> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/ask/flat/chapter-40-freebsd-kernel-architecture/di-40.4-jie-ji-qi-wu-guan-de-nei-he-xuan-xiang-zhu-jie.md). # 40.4 Machine-Independent Kernel Options Machine-independent options form the core abstraction layer of the kernel, enabling cross-hardware-platform portability. This section translates and annotates the general configuration options in **sys/conf/NOTES**, listing the original text and English interpretations by functional category. * Source: [freebsd-src/main/sys/conf/NOTES](https://github.com/freebsd/freebsd-src/blob/main/sys/conf/NOTES) * Version: [random: allow disabling of entropy harvesting from keyboard & mice](https://github.com/freebsd/freebsd-src/commit/d6f10a5d013fdcc92847644ffbaf65cbf491bb39) > **Tip** > > You can directly cut and paste the entries below into the kernel configuration file. > > > Lines starting with `device`, `options`, `machine`, `ident`, `maxusers`, `makeoptions`, `hints`, etc. should be placed in the kernel configuration file where config(8) will be run. > > > > Lines starting with `envvar hint.` should be placed in the hints file. > > > > For kernel test builds, use `make LINT` to create the old-style LINT file. > > > > This file contains machine-independent kernel configuration notes. > **Tip** > > NOTES conventions and style guide: > > Large comment blocks should begin and end with a line containing only the comment character. > > When describing a specific object, if a block comment exists, it should be written first. Next, write device, options, and hints entries in that order. All device and option lines must have comments, and the comments must not merely repeat the device or option name. Where possible, comments should be concise and placed on the same line. Detailed descriptions of devices and subsystems should be placed in manual pages. > > `options` and the option name are separated by one space plus one tab. `device` and the device name are separated by two spaces plus one tab. Comments after an option or device should have one space after the comment character. To comment out disabling negative options (and thus should not be enabled in a LINT build), prefix with `#!` before `options`. ```ini ident LINT ``` This is the kernel "identifier," which should typically be the same as the kernel name. ```ini maxusers 10 ``` The `maxusers` parameter controls the static sizing of multiple internal system tables through formulas defined in `subr_param.c`. Omitting this parameter or setting it to `0` allows the system to automatically adjust sizes based on physical memory. ```ini #hints "LINT.hints" # Default location to find device hints ``` Statically compile device connection information instead of using **/boot/device.hints**. ```ini #env "LINT.env" ``` Use the above method to compile values into the kernel so that the kernel can access them via `getenv()` (or kenv(1) from user space). The file format is `variable=value`; see [kenv(1)](https://man.freebsd.org/cgi/man.cgi?query=kenv\&sektion=1) for details. ```ini makeoptions CONF_CFLAGS=-fno-builtin # ①② Disable gcc built-in functions such as memcmp #makeoptions DEBUG=-g # ③ Build a kernel with gdb(1) debugging symbols #makeoptions KERNEL=foo # ④ Build kernel "foo" and install to "/foo" #makeoptions MODULES_OVERRIDE="ext2fs sound/sound sound/driver/maestro3" # ⑤ Only build ext2fs module and required sound system parts makeoptions DESTDIR=/tmp # Temporarily set the target installation directory to /tmp ``` * ①: `makeoptions` parameters can pass variables to the Makefile generated in the build area. * ②: `CONF_CFLAGS` provides additional compiler flags that are appended to `${CFLAGS}` after most other flags. Here it is used to disable the use of non-optimal gcc built-in functions (such as `memcmp`). * ③: `DEBUG` is a special flag. The following approach is equivalent to running `config -g KERNELNAME`, which generates `kernel.debug` with debugging information `-g`, and also generates a normal `kernel`. Use `make install.debug` to install the debug kernel, but since the kernel does not load debug symbols, this is usually unnecessary. * ④: Renames `KERNEL`, i.e., changes the default name of the kernel. * ⑤: `MODULES_OVERRIDE` can be used to restrict the list of modules built, compiling only the specified modules. ```ini options MAXDSIZ=(1024UL*1024*1024) options MAXSSIZ=(128UL*1024*1024) options DFLDSIZ=(1024UL*1024*1024) ``` FreeBSD processes have certain limits when using system resources. For more details, see: getrlimit(2)\[EB/OL]. \[2026-03-26]. . Each resource limit has two values: a "soft limit" and a "hard limit." The soft limit can be modified during normal system operation, while the hard limit can only be set at boot time. Their default values are defined in **sys/architecture/include/vmparam.h**. There are two ways to modify the above limits: 1. Set values at kernel compile time. The following options can raise the limit to 1 GB. These values can be further increased by modifying the relevant parameters. 2. Set tunable parameters in the **/boot/loader.conf** file: `kern.maxswzone`, `kern.maxbcache`, `kern.maxtsiz`, `kern.dfldsiz`, `kern.maxdsiz`, `kern.dflssiz`, `kern.maxssiz`, and `kern.sgrowsiz`. Settings in the **/boot/loader.conf** file override any values in the kernel configuration file. For more details, see the function `init_param1` in **sys/kern/subr\_param.c**. It is recommended to use the **/boot/loader.conf.local** file to extend local configuration and avoid directly modifying the **/boot/loader.conf** file. ```ini options BLKDEV_IOSIZE=8192 ``` `BLKDEV_IOSIZE` can set the default block size used for user block device I/O. > **Note** > > When specifying a block device via a label with a non-zero partition block size, the label overrides this value. The default value is `PAGE_SIZE`. ```ini options DFLTPHYS=(64*1024) # DFLTPHYS indicates the safe size for raw I/O block device access, default 64K options MAXPHYS=(128*1024) # MAXPHYS indicates the maximum size for raw I/O block device access, default 128K on ILP32 platforms and 1M on LP64 platforms ``` For known reliable devices, read/write operations will be split into MAXPHYS-sized chunks; for other devices, DFLTPHYS-sized chunks are used. Some applications perform better with larger raw I/O access blocks. > **Note** > > Some virtual memory (VM) parameters are derived from these values; setting them too large may prevent the kernel from booting. ```ini options INCLUDE_CONFIG_FILE # Embed this file into the kernel ``` This configuration file can be actually stored in the kernel binary. See config(8) for details. ```ini options BOOTVERBOSE=1 options BOOTHOWTO=RB_MULTIPLE ``` Compile-time defaults for various boot parameters. ```ini options BOOT_TAG=\"\" ``` Compile-time default for the `dmesg` boot tag. Default boot tag; can be overridden using the loader tunable `kern.boot_tag`. The current boot tag is also exposed via the sysctl `kern.boot_tag`. ```ini options BOOT_TAG_SZ=32 ``` Maximum boot tag size that the kernel static buffer should accommodate. Maximum size of BOOT\_TAG and its related tunables. ```ini options GEOM_CACHE # Disk cache options GEOM_CONCAT # Disk concatenation options GEOM_ELI # Disk encryption options GEOM_GATE # Userland service options GEOM_JOURNAL # Journaling options GEOM_LABEL # Provider labeling options GEOM_LINUX_LVM # Linux LVM2 volumes options GEOM_MAP # Map-based partitioning options GEOM_MIRROR # Disk mirroring options GEOM_MULTIPATH # Disk multipathing options GEOM_NOP # Test class options GEOM_PART_APM # Apple partitioning options GEOM_PART_BSD # BSD disklabels options GEOM_PART_BSD64 # BSD disklabels 64 options GEOM_PART_EBR # Extended Boot Records options GEOM_PART_GPT # GPT partitions options GEOM_PART_LDM # Logical Disk Manager options GEOM_PART_MBR # MBR partitions options GEOM_RAID # Software RAID functionality options GEOM_RAID3 # RAID3 functionality options GEOM_SHSEC # Shared secret options GEOM_STRIPE # Disk striping options GEOM_UZIP # Read-only compressed disks options GEOM_VIRSTOR # Virtual storage options GEOM_ZERO # Performance testing helper ``` GEOM-related options. ```ini options ROOTDEVNAME=\"ufs:da0s2e\" ``` The root device and filesystem type can be specified at compile time; if the bootloader cannot correctly identify the root device, this provides a fallback; or specify the `RB_DFLTROOT` flag (`-r`) at kernel boot time to override the option. ## Scheduler The scheduler is the core component in the kernel responsible for allocating CPU time to different threads and processes. ```ini options SCHED_4BSD # Historic, battle-tested BSD scheduler options SCHED_STATS # Statistics #options SCHED_ULE # Default ULE scheduler ``` Either `SCHED_4BSD` or `SCHED_ULE` must be selected. These options select which scheduler to compile into the kernel. Explanation: * `SCHED_4BSD` uses global run queues and has no CPU affinity, which results in relatively limited performance on SMP systems. However, it has excellent interactivity and priority selection capabilities. Since FreeBSD 7.1, `SCHED_ULE` has replaced `SCHED_4BSD` as the default scheduler. `SCHED_4BSD` is only meaningful on uniprocessor systems or in specific debugging scenarios; `SCHED_ULE` is recommended on modern SMP systems. * `SCHED_ULE` provides significant performance advantages over 4BSD on many SMP machine workloads. It supports CPU affinity, per-CPU run queues, and scheduler locks. It also has stronger support for interactivity, providing better responsiveness even on uniprocessor machines. * `SCHED_STATS` saves some statistics under the sysctl `kern.sched.stats`, which is helpful for debugging scheduling decisions. ## SMP Symmetric MultiProcessor (SMP) systems contain multiple processor cores that share memory and other resources. ```ini options SMP # Symmetric MultiProcessor (SMP) kernel ``` SMP builds a symmetric multiprocessor kernel. Must be specified. ```ini options EARLY_AP_STARTUP ``` `EARLY_AP_STARTUP` releases application processors earlier during kernel startup (before device probing), rather than at the end of startup. This option was used as a transitional option during the migration from late to early AP startup. ```ini options MAXCPU=32 ``` `MAXCPU` defines the maximum number of CPUs that can be started in the system. Each architecture typically already has a default value. ```ini options NUMA ``` NUMA enables support for Non-Uniform Memory Access policies in various kernel subsystems. ```ini options MAXMEMDOM=2 ``` `MAXMEMDOM` defines the maximum number of memory domains that can be started in the system. Each architecture typically already has a default value. ```ini options NO_ADAPTIVE_MUTEXES ``` `ADAPTIVE_MUTEXES` changes the behavior of blocking mutexes: if the thread currently holding the mutex is executing on another CPU, the mutex spins. This behavior is enabled by default; this option can be used to disable the above behavior. ```ini options NO_ADAPTIVE_RWLOCKS ``` `ADAPTIVE_RWLOCKS` changes the behavior of read-write locks: if the thread currently holding the read-write lock is executing on another CPU, the lock spins. This behavior is enabled by default; this option can be used to disable the above behavior. ```ini options NO_ADAPTIVE_SX ``` `ADAPTIVE_SX` changes the behavior of sx locks: if the thread currently holding the sx lock is executing on another CPU, the lock spins. This behavior is enabled by default; this option can be used to disable the above behavior. ```ini options MUTEX_NOINLINE ``` `MUTEX_NOINLINE` forces mutex operations to call a function for each operation rather than inlining the simple cases. Can be used to reduce the kernel text segment size. > **Note** > > The options `INVARIANT_SUPPORT`, `INVARIANTS`, `KTR`, `LOCK_PROFILING`, and `WITNESS` implicitly enable this behavior. ```ini options RWLOCK_NOINLINE ``` `RWLOCK_NOINLINE` forces read-write lock operations to call a function for each operation rather than inlining the simple cases. Can be used to reduce the kernel text segment size. > **Note** > > The options `INVARIANT_SUPPORT`, `INVARIANTS`, `KTR`, `LOCK_PROFILING`, and `WITNESS` implicitly enable this behavior. ```ini options SX_NOINLINE ``` `SX_NOINLINE` forces sx lock operations to call a function for each operation rather than inlining the simple cases. This can be used to reduce the kernel text segment size. > **Note** > > This behavior is implicitly enabled by the options `INVARIANT_SUPPORT`, `INVARIANTS`, `KTR`, `LOCK_PROFILING`, and `WITNESS`. ### SMP Debugging Options The following are kernel configuration options related to SMP debugging. ```ini options PREEMPTION options FULL_PREEMPTION options WITNESS options WITNESS_KDB options WITNESS_SKIPSPIN ``` * `CALLOUT_PROFILING`: Enable basic profiling of the callwheel data structure used by the [callout(9)](https://man.freebsd.org/cgi/man.cgi?query=callout\&sektion=9) backend. * `PREEMPTION`: Allows higher-priority interrupt threads to preempt threads in the kernel. Improves interactivity by enabling interrupt threads to run sooner rather than waiting. * `FULL_PREEMPTION`: Instructs the kernel to preempt non-realtime kernel threads. Primarily used during development to expose race conditions and other defects. Enabling it degrades performance and increases kernel panic frequency. Depends on the `PREEMPTION` option; not recommended to enable. * `SLEEPQUEUE_PROFILING`: Basic profiling that saves hash tables of active sleep queues and the frequency of sleep wait messages. * `TURNSTILE_PROFILING`: Basic profiling that saves hash tables of active lock queues. * `UMTX_PROFILING`: Basic profiling that saves hash tables of active lock queues. * `WITNESS`: Enables witness code to detect deadlocks and cycles during lock operations. * WITNESS\_KDB: Enter the kernel debugger on lock hierarchy violations or when a thread holds a lock before sleeping. * WITNESS\_SKIPSPIN: Disable witness checks on spin mutexes. ```ini options LOCK_PROFILING ``` `LOCK_PROFILING` — lock profiling. See [LOCK\_PROFILING(9)](https://man.freebsd.org/cgi/man.cgi?query=LOCK_PROFILING\&sektion=9) for details. ```ini options MPROF_BUFFERS="1536" # Set number of buffers options MPROF_HASH_SIZE="1543"# Set buffer hash table size ``` The `MPROF_HASH_SIZE` hash table size must be greater than the number of buffers `MPROF_BUFFERS` and should be a prime number. ```ini options CALLOUT_PROFILING ``` Profiling for the [callout(9)](https://man.freebsd.org/cgi/man.cgi?query=callout\&sektion=9) backend. ```ini options SLEEPQUEUE_PROFILING options TURNSTILE_PROFILING options UMTX_PROFILING ``` Profiling of internal hash tables. ```ini options EPOCH_TRACE ``` Debug tracing for [epoch(9)](https://man.freebsd.org/cgi/man.cgi?query=epoch\&sektion=9) misuse. ## Compatibility Compatibility options allow the kernel to support system calls and interfaces from older versions of FreeBSD, thereby running programs written for those older versions. ```ini options COMPAT_43TTY ``` Legacy TTY interface. ```ini options COMPAT_FREEBSD4 ``` Enable FreeBSD 4 compatibility system calls. FreeBSD 4 was released in 2000, over 20 years ago, and applications actually requiring this compatibility layer are extremely rare. This option has been removed from streamlined kernel configurations such as MINIMAL; it is recommended to enable it only when there is a confirmed need for legacy binary programs. > **Note** > > In general, `COMPAT_FREEBSD` depends on `COMPAT_FREEBSD`, `COMPAT_FREEBSD`, etc. ```ini options COMPAT_FREEBSD5 ``` Enable FreeBSD 5 compatibility system calls. FreeBSD 5 was released in 2003, over 20 years ago; actual demand is extremely low. ```ini options COMPAT_FREEBSD6 ``` Enable FreeBSD 6 compatibility system calls. FreeBSD 6 was released in 2005, over 20 years ago; actual demand is extremely low. ```ini options COMPAT_FREEBSD7 ``` Enable FreeBSD 7 compatibility system calls. FreeBSD 7 was released in 2008, over 15 years ago; actual demand is extremely low. This option has been removed from streamlined kernel configurations such as MINIMAL. ```ini options COMPAT_FREEBSD8 ``` Enable FreeBSD 8 compatibility system calls. ```ini options COMPAT_FREEBSD9 ``` Enable FreeBSD 9 compatibility system calls. ```ini options COMPAT_FREEBSD10 ``` Enable FreeBSD 10 compatibility system calls. ```ini options COMPAT_FREEBSD11 ``` Enable FreeBSD 11 compatibility system calls. ```ini options COMPAT_FREEBSD12 ``` Enable FreeBSD 12 compatibility system calls. ```ini options COMPAT_FREEBSD13 ``` Enable FreeBSD 13 compatibility system calls. ```ini options COMPAT_FREEBSD14 ``` Enable FreeBSD 14 compatibility system calls. ```ini options COMPAT_LINUXKPI ``` Enable Linux Kernel Programming Interface. ```ini options SYSVSHM options SYSVSEM options SYSVMSG ``` * `SYSVSHM`: Enable System V-style shared memory support. * `SYSVSEM`: Enable System V-style semaphore support. * `SYSVMSG`: Enable System V-style message queue support. ## Debugging Debugging options are used to enable debugging features in the kernel, including the kernel debugger, call stack tracing, lock verification, and other functions to help developers diagnose and fix problems. ```ini options KDB ``` Compile kernel debugger-related code at build time. ```ini options KDB_TRACE ``` Print the call stack trace of the current thread on the console when the system panics. ```ini options KDB_UNATTENDED ``` Do not enter the debugger on panic. Suitable for unattended operating environments; if you need to manually enter the debugger from the console but still want the system to recover on its own after a panic, this option can be enabled. ```ini options DDB ``` Enable the ddb debugger backend. ```ini options DDB_NUMSYM ``` Print numeric values of symbols in addition to symbolic representation. ```ini options GDB ``` Enable the remote gdb debugger backend. ```ini options QUEUE_MACRO_DEBUG_TRASH ``` Trash list pointers when they become invalid (i.e., when elements are removed from the list). Relatively low cost to enable. ```ini #options QUEUE_MACRO_DEBUG_TRACE ``` Store information about the last caller that modified the list object in the list object. Requires additional memory overhead. ```ini options SYSCTL_DEBUG ``` When `SYSCTL_DEBUG` is enabled, it generates a sysctl debug tree that can be used to dump the contents of registered sysctl nodes on the console. Because it generates overly verbose console output that may interfere with serial console operations, it is disabled by default. ```ini options TEXTDUMP_PREFERRED ``` Enable textdump by default and disable kernel core dumps. ```ini options TEXTDUMP_VERBOSE ``` Enable additional debug information when performing a textdump. ```ini options NO_SYSCTL_DESCR ``` `NO_SYSCTL_DESCR` omits sysctl node descriptions to save space in the generated kernel. ```ini options MALLOC_DEBUG_MAXZONES=8 ``` `MALLOC_DEBUG_MAXZONES` enables multiple uma zones for [malloc(9)](https://man.freebsd.org/cgi/man.cgi?query=malloc\&sektion=9) allocations smaller than one page. Its purpose is to isolate different malloc types into hash categories, so that all buffer overflows and use-after-free (UAF) issues typically only affect memory of malloc types within that hash category. This is purely a debugging tool; by changing the hash function and tracking the corrupted hash category, the intersection of hash categories across instances can point to the single abusive malloc type. At that point, inspection or [memguard(9)](https://man.freebsd.org/cgi/man.cgi?query=memguard\&sektion=9) can be used to catch the offending code. ```ini options DEBUG_MEMGUARD ``` `DEBUG_MEMGUARD` builds and enables memguard(9), an alternative allocator for the kernel used to detect scenarios such as use-after-free (UAF). ```ini options DEBUG_REDZONE ``` `DEBUG_REDZONE` enables buffer underflow and buffer overflow detection for [malloc(9)](https://man.freebsd.org/cgi/man.cgi?query=malloc\&sektion=9). ```ini #options EARLY_PRINTF ``` `EARLY_PRINTF` allows a special `printf` (`eprintf`) to be used very early in the kernel (before `cn_init()` is called). This is typically only used for early boot debugging. Since this functionality is generally unavailable and the required `eputc()` is also undefined, it is normally not defined and is commented out here. ```ini options KTRACE # Kernel tracing options KTRACE_REQUEST_POOL=101 ``` `KTRACE` enables the system call tracing facility [ktrace(2)](https://man.freebsd.org/cgi/man.cgi?query=ktrace\&sektion=2). For better SMP support, KTRACE uses a worker thread to asynchronously process most trace events rather than having the generating thread process them directly. This requires pre-allocating a pool for storing trace event objects. The `KTRACE_REQUEST_POOL` option specifies the initial size of this pool. ```ini options KTR options KTR_BOOT_ENTRIES=1024 options KTR_ENTRIES=(128*1024) options KTR_COMPILE=(KTR_ALL) options KTR_MASK=KTR_INTR options KTR_CPUMASK=0x3 options KTR_VERBOSE ``` KTR is a kernel tracing facility ported from BSD/OS. It is enabled via the `KTR` option. * `KTR_ENTRIES` defines the number of entries in the circular trace buffer; it can be any number. * `KTR_BOOT_ENTRIES` defines the number of entries during early boot, used before [malloc(9)](https://man.freebsd.org/cgi/man.cgi?query=malloc\&sektion=9) is available. * `KTR_COMPILE` defines the event mask to compile into the kernel, defined by the `KTR_*` constants in ``. * `KTR_MASK` defines the initial value of the variable `ktr_mask`, which determines at runtime which events to trace. * `KTR_CPUMASK` determines which CPUs record events; bit X corresponds to CPU X. The value of this option can be a series of comma-separated bitmasks. (e.g.: `KTR_CPUMASK=0xAF,0xFFFFFFFFFFFFFFFF`). * `KTR_VERBOSE` enables KTR event output to the console by default. This feature can be adjusted via the sysctl `debug.ktr.verbose`; if `KTR_VERBOSE` is not defined, it is disabled by default. For details, see: ktr(4)\[EB/OL]. \[2026-03-26]. and ktrdump(8)\[EB/OL]. \[2026-03-26]. . ```ini options ALQ options KTR_ALQ ``` * [ALQ(9)](https://man.freebsd.org/cgi/man.cgi?query=alq\&sektion=9) is a mechanism for asynchronously queuing kernel records to a vnode. * Services such as [ktr(4)](https://man.freebsd.org/cgi/man.cgi?query=ktr\&sektion=4) use it to generate trace files based on the kernel event stream. Records are written asynchronously by a worker thread. ```ini options INVARIANTS ``` The `INVARIANTS` option is used in multiple source files to enable additional integrity checks on internal structures. Since checking these conditions consumes additional time and related issues are typically only caused by programming errors, this option is disabled by default. ```ini options INVARIANT_SUPPORT ``` The `INVARIANT_SUPPORT` option adds verification support for some internal structures at compile time. Since enabling `INVARIANTS` calls these verification functions, `INVARIANT_SUPPORT` is a prerequisite for enabling `INVARIANTS`. The purpose of this is to allow `INVARIANTS` to be set for individual source files (by modifying the source file or specifying on the command line) after `INVARIANT_SUPPORT` is enabled. If you want to build kernel modules with `INVARIANTS`, adding `INVARIANT_SUPPORT` to the kernel provides all the necessary infrastructure without additional overhead. ```ini options KASSERT_PANIC_OPTIONAL ``` The `KASSERT_PANIC_OPTIONAL` option allows kasserts to not necessarily cause a panic when triggered. Panic is the default behavior, but runtime options can turn it off entirely or disable it under set limits. ```ini options DIAGNOSTIC ``` The `DIAGNOSTIC` option enables additional debugging information and integrity checks. Since these additional checks are too costly or too verbose for `INVARIANTS` kernels, they are disabled by default. Typically, a kernel configured with `DIAGNOSTIC` also enables the `INVARIANTS` option. ```ini options REGRESSION ``` `REGRESSION` enables optional kernel interfaces that are only needed in regression testing. Enabling these interfaces may pose a security risk, as they allow processes to easily modify certain aspects of the runtime environment, reproducing unlikely or anomalous (possibly normally impossible) scenarios. ```ini options COMPILING_LINT ``` This option allows certain drivers that cannot coexist in a running system to coexist. It is used to compile all kernel code at once for quality assurance (such as this file, whose name derives from this option). ```ini options STACK ``` STACK enables the [stack(9)](https://man.freebsd.org/cgi/man.cgi?query=stack\&sektion=9) facility, which can capture kernel stacks. If [DDB(4)](https://man.freebsd.org/cgi/man.cgi?query=ddb\&sektion=4) is compiled into the kernel, [stack(9)](https://man.freebsd.org/cgi/man.cgi?query=stack\&sektion=9) is also automatically compiled in. ```ini options NUM_CORE_FILES=5 ``` The `NUM_CORE_FILES` option specifies the upper limit on the number of core files generated by a specific process. This option takes effect when the core file format specifier includes the `%I` pattern. Since the core count in the format string is only `1` character, the representable range is 0-9, so the maximum value allowed by this option is `10` (i.e., specifying this parameter as `9`). The core file count limit can be adjusted at runtime via the sysctl `debug.ncores`. ```ini options TSLOG options TSLOGSIZE=262144 ``` The `TSLOG` option enables timestamped recording of events, particularly function entry/exit, to track time consumed by the kernel. Since more advanced tools such as DTrace are not yet available at that point, this option is especially useful during early boot. * The `TSLOGSIZE` option controls the size of the (pre-allocated, fixed-length) buffer used to store these events (default: `262144` records). * The `TSLOG_PAGEZERO` option enables TSLOG for `pmap_zero_page`; since it typically generates too many records to be practical, it must be explicitly enabled. For security reasons, TSLOG should not be enabled on production systems. ## Performance Monitoring Performance monitoring options provide the ability to measure and analyze system performance, particularly utilizing CPU built-in performance monitoring counters. ```ini device hwpmc # Driver (also available as a loadable module) options HWPMC_DEBUG options HWPMC_HOOKS # Additional required kernel hooks ``` The `hwpmc` driver can monitor performance using CPU built-in performance monitoring counters. The base kernel needs to be configured via `options` entries; the hwpmc device can be compiled into the kernel or loaded as a loadable kernel module. Additional configuration options may be required on specific architectures; see: hwpmc(4)\[EB/OL]. \[2026-03-26]. . ## Network Interfaces Network interfaces are a key part of the FreeBSD kernel responsible for handling network communication, including protocol stacks, network device drivers, etc. ### Protocol Stack The network protocol stack is responsible for handling the transmission and reception of network data, including protocols such as TCP/IP and UDP. ```ini options INET # Internet communications protocol (IPv4) options INET6 # Internet communications protocol (IPv6) ``` ```ini options CC_CDG # CAIA Delay-Gradient algorithm options CC_CHD # CAIA Hamilton-Delay algorithm options CC_CUBIC # Cubic algorithm options CC_DCTCP # DCTCP algorithm options CC_HD # Hamilton Delay algorithm options CC_HTCP # H-TCP algorithm options CC_NEWRENO # NewReno algorithm options CC_VEGAS # Vegas algorithm options CC_DEFAULT=\"cubic\" # Specify Cubic as the default congestion control algorithm options RATELIMIT # Transmit rate limiting support options ROUTETABLES=2 # Allocate up to 65536 FIBs. Default is 1, but this is not recommended as each FIB entry consumes significant memory options TCP_OFFLOAD # TCP offload options TCP_RFC7413 # TCP Fast Open options TCPHPTS # Enable TCP HPTS (High Precision Timer) support #options TCP_HPTS_KTEST # Add KTEST support for HPTS ``` > **Note** > > If the options `INET`, `INET6`, or both are used: at least one congestion control option must be specified, otherwise compilation will fail. `GENERIC` defines `CC_CUBIC`. If multiple congestion controls are compiled, a default value may need to be specified. The string in `default` is the name of the `cc` module, used in sysctl to set the default. The code defines `CUBIC` as the default, or if only one `cc_module` is compiled, that module is used. ```ini options IPSEC # IPsec (requires device crypto support) ``` IPsec (IP Security). To enable `IPSEC`, device crypto support **must** also be specified in the kernel configuration. ```ini options IPSEC_SUPPORT #options IPSEC_DEBUG # IPsec debugging ``` The `IPSEC_SUPPORT` option does not directly enable IPsec, but it allows IPsec to be loaded as a kernel module. Device crypto support **must** still be added to the kernel configuration. ```ini options TCP_BBR # BBR (Bottleneck Bandwidth and Round-trip propagation time) options TCP_RACK # RACK stack, Recent ACKnowledgment ``` Optional TCP stacks. ```ini options KERN_TLS # TLS send and receive offload ``` TLS is used for framing and encrypting/decrypting data over TCP sockets. ```ini options NETLINK ``` Netlink is a message passing interface between the kernel and user space. ```ini options NETSMB # SMB/CIFS requester ``` SMB/CIFS requester. NETSMB enables support for the SMB protocol; it requires the `LIBMCHAIN` and `LIBICONV` options. ```ini options LIBMCHAIN ``` mchain library. It can be loaded as a KLD (loadable kernel module) or compiled into the kernel. ```ini options LIBALIAS ``` libalias library, used for performing NAT (Network Address Translation). ```ini options SCTP options SCTP_SUPPORT ``` SCTP is a transport layer protocol originally defined by RFC 2960, later updated by RFC 3309 and RFC 3758; RFC 4960, published in 2007, superseded RFC 2960 and RFC 3309 as the new base specification, subsequently updated by RFC 6096, RFC 7053, etc.; RFC 9260, published in 2022, further superseded RFC 4960 (IETF. RFC 9260: Stream Control Transmission Protocol\[EB/OL]. (2022-05). \[2026-04-19]. ). This version supports all extensions, including many drafts (most of which are about to become RFCs). It is the reference implementation of SCTP and has been thoroughly tested. > **Note** > > **Both INET and INET6 must be defined**. It is not necessary to enable IPv6, but SCTP is a dual-stack protocol because an association can span both IPv6 and IPv4 addresses; IPv6 and IPv4 have not yet been separated. The `SCTP_SUPPORT` option does not directly enable SCTP, but provides the support needed to load SCTP as a loadable kernel module. ```ini options SCTP_DEBUG ``` The following are SCTP debugging options: `SCTP_DEBUG` enables various verbose print functions. It is controlled by a bitmask (settable via socket options and sysctl). Including this option alone does not immediately produce logs; the corresponding bits must be set first. However, the print output can be very verbose. Therefore, if the option is not enabled, the code will not perform bit checks and printing, which improves running speed. Do not use unless for debugging purposes. ```ini options SCTP_LOCK_LOGGING options SCTP_MBUF_LOGGING options SCTP_MBCNT_LOGGING options SCTP_PACKET_LOGGING options SCTP_LTRACE_CHUNKS options SCTP_LTRACE_ERRORS ``` All the above options are used to enable specific types of logging. They can monitor congestion window (CWND) growth, flight size, and various other metrics. See the code for more details. Using these features requires enabling [ktr(4)](https://man.freebsd.org/cgi/man.cgi?query=ktr\&sektion=4), then setting various log bits via sysctl to turn them on or off. Use [ktrdump(8)](https://man.freebsd.org/cgi/man.cgi?query=ktrdump\&sektion=8) to extract logs, then process them with a display program to generate charts and other visualizations. ```ini options OFED options OFED_DEBUG_INIT ``` OpenFabrics Enterprise Distribution (OFED, InfiniBand). ```ini options SDP options SDP_DEBUG ``` Sockets Direct Protocol (SDP). ```ini options IPOIB # InfiniBand protocol stack and support options IPOIB_DEBUG options IPOIB_CM # Use connected mode IPoIB ``` IP over InfiniBand (IPoIB), Internet Protocol based on InfiniBand, see: wiki/InfiniBand\[EB/OL]. \[2026-03-26]. . ```ini options ALTQ # Alternate queuing options ALTQ_CBQ # Class-Based Queuing options ALTQ_RED # Random Early Detection options ALTQ_RIO # RED In/Out options ALTQ_CODEL # CoDel active queue management options ALTQ_HFSC # Hierarchical Fair Service Curve scheduler options ALTQ_FAIRQ # Fair packet scheduler options ALTQ_CDNR # Traffic conditioner options ALTQ_PRIQ # Priority queue options ALTQ_NOPCC # Required when TSC is unavailable options ALTQ_DEBUG # Enable ALTQ debugging ``` [altq(9)](https://man.freebsd.org/cgi/man.cgi?query=altq\&sektion=9). The base part enabling hooks via the `ALTQ` option. Individual scheduling policies must be compiled into the base system and cannot be loaded as modules at this stage. ALTQ requires a stable TSC; if the TSC is unstable or changes during CPU throttling, the `ALTQ_NOPCC` option must also be enabled. ```ini options NETGRAPH # netgraph(4) system ① options NETGRAPH_DEBUG # Enable extra debugging for netgraph(4) and its nodes ``` * ①: The [netgraph(4)](https://man.freebsd.org/cgi/man.cgi?query=netgraph\&sektion=4) system is a networking toolkit. Use the `NETGRAPH` option to enable netgraph core code. Individual node types can be enabled via the corresponding options below; however, this is not strictly necessary because if a node type has not been compiled into the kernel, netgraph will automatically load the corresponding KLD module. Each type below has a corresponding manual page, e.g., [ng\_async(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_async\&apropos=0\&sektion=4). ```ini options NETGRAPH_ASYNC # ng_async(4) options NETGRAPH_BLUETOOTH # ng_bluetooth(4) options NETGRAPH_BLUETOOTH_HCI # ng_hci(4) options NETGRAPH_BLUETOOTH_L2CAP # ng_l2cap(4) options NETGRAPH_BLUETOOTH_SOCKET # ng_btsocket(4) options NETGRAPH_BLUETOOTH_UBT # ng_ubt(4) options NETGRAPH_BLUETOOTH_UBTBCMFW # ubtbcmfw(4) options NETGRAPH_BPF # ng_bpf(4) options NETGRAPH_BRIDGE # ng_bridge(4) options NETGRAPH_CAR # ng_car(4) options NETGRAPH_CHECKSUM # ng_checksum(4) options NETGRAPH_CISCO # ng_cisco(4) options NETGRAPH_DEFLATE # ng_deflate(4) options NETGRAPH_DEVICE # ng_device(4) options NETGRAPH_ECHO # ng_echo(4) options NETGRAPH_EIFACE # ng_eiface(4) options NETGRAPH_ETHER # ng_ether(4) options NETGRAPH_FRAME_RELAY # ng_frame_relay(4) options NETGRAPH_GIF # ng_gif(4) options NETGRAPH_GIF_DEMUX # ng_gif_demux(4) options NETGRAPH_HOLE # ng_hole(4) options NETGRAPH_IFACE # ng_iface(4) options NETGRAPH_IP_INPUT # ng_ip_input(4) options NETGRAPH_IPFW # ng_ipfw(4) options NETGRAPH_KSOCKET # ng_ksocket(4) options NETGRAPH_L2TP # ng_l2tp(4) options NETGRAPH_LMI # ng_lmi(4) options NETGRAPH_MPPC_COMPRESSION # ng_mppc(4) options NETGRAPH_MPPC_ENCRYPTION # ng_mppc(4) options NETGRAPH_NETFLOW # ng_netflow(4) options NETGRAPH_NAT # ng_nat(4) options NETGRAPH_ONE2MANY # ng_one2many(4) options NETGRAPH_PATCH # ng_patch(4) options NETGRAPH_PIPE # ng_pipe(4) options NETGRAPH_PPP # ng_ppp(4) options NETGRAPH_PPPOE # ng_pppoe(4) options NETGRAPH_PPTPGRE # ng_pptpgre(4) options NETGRAPH_PRED1 # ng_pred1(4) options NETGRAPH_RFC1490 # ng_rfc1490(4) options NETGRAPH_SOCKET # ng_socket(4) options NETGRAPH_SPLIT # ng_split(4) options NETGRAPH_TAG # ng_tag(4) options NETGRAPH_TCPMSS # ng_tcpmss(4) options NETGRAPH_TEE # ng_tee(4) options NETGRAPH_UI # ng_UI(4) options NETGRAPH_VJC # ng_vjc(4) options NETGRAPH_VLAN # ng_vlan(4) ``` netgraph node types: * NETGRAPH\_ASYNC --- [ng\_async(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_async\&apropos=0\&sektion=4) * NETGRAPH\_BLUETOOTH --- [ng\_bluetooth(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_bluetooth\&sektion=4) * NETGRAPH\_BLUETOOTH\_HCI --- [ng\_hci(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_hci\&sektion=4) * NETGRAPH\_BLUETOOTH\_L2CAP --- [ng\_l2cap(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_l2cap\&sektion=4) * NETGRAPH\_BLUETOOTH\_SOCKET --- [ng\_btsocket(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_btsocket\&sektion=4) * NETGRAPH\_BLUETOOTH\_UBT --- [ng\_ubt(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_ubt\&sektion=4) * NETGRAPH\_BLUETOOTH\_UBTBCMFW --- [ubtbcmfw(4)](https://man.freebsd.org/cgi/man.cgi?query=ubtbcmfw\&sektion=4) * NETGRAPH\_BPF --- [ng\_bpf(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_bpf\&sektion=4) * NETGRAPH\_BRIDGE --- [ng\_bridge(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_bridge\&sektion=4) * NETGRAPH\_CAR --- [ng\_car(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_car\&sektion=4) * NETGRAPH\_CHECKSUM --- [ng\_checksum(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_checksum\&sektion=4) * NETGRAPH\_CISCO --- [ng\_cisco(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_cisco\&sektion=4) * NETGRAPH\_DEFLATE --- [ng\_deflate(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_deflate\&sektion=4) * NETGRAPH\_DEVICE --- [ng\_device(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_device\&sektion=4) * NETGRAPH\_ECHO --- [ng\_echo(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_echo\&sektion=4) * NETGRAPH\_EIFACE --- [ng\_eiface(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_eiface\&sektion=4) * NETGRAPH\_ETHER --- [ng\_ether(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_ether\&sektion=4) * NETGRAPH\_FRAME\_RELAY --- [ng\_frame\_relay(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_frame_relay\&sektion=4) * NETGRAPH\_GIF --- [ng\_gif(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_gif\&sektion=4) * NETGRAPH\_GIF\_DEMUX --- [ng\_gif\_demux(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_gif_demux\&sektion=4) * NETGRAPH\_HOLE --- [ng\_hole(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_hole\&sektion=4) * NETGRAPH\_IFACE --- [ng\_iface(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_iface\&sektion=4) * NETGRAPH\_IP\_INPUT --- [ng\_ip\_input(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_ip_input\&sektion=4) * NETGRAPH\_IPFW --- [ng\_ipfw(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_ipfw\&sektion=4) * NETGRAPH\_KSOCKET --- [ng\_ksocket(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_ksocket\&sektion=4) * NETGRAPH\_L2TP --- [ng\_l2tp(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_l2tp\&sektion=4) * NETGRAPH\_LMI --- [ng\_lmi(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_lmi\&sektion=4) * NETGRAPH\_MPPC\_COMPRESSION --- [ng\_mppc(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_mppc\&sektion=4) * NETGRAPH\_MPPC\_ENCRYPTION --- [ng\_mppc(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_mppc\&sektion=4) * NETGRAPH\_NETFLOW --- [ng\_netflow(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_netflow\&sektion=4) * NETGRAPH\_NAT --- [ng\_nat(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_nat\&sektion=4) * NETGRAPH\_ONE2MANY --- [ng\_one2many(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_one2many\&sektion=4) * NETGRAPH\_PATCH --- [ng\_patch(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_patch\&sektion=4) * NETGRAPH\_PIPE --- [ng\_pipe(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_pipe\&apropos=0\&sektion=4) * NETGRAPH\_PPP --- [ng\_ppp(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_ppp\&sektion=4) * NETGRAPH\_PPPOE --- [ng\_pppoe(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_pppoe\&sektion=4) * NETGRAPH\_PPTPGRE --- [ng\_pptpgre(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_pptpgre\&sektion=4) * NETGRAPH\_PRED1 --- [ng\_pred1(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_pred1\&sektion=4) * NETGRAPH\_RFC1490 --- [ng\_rfc1490(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_rfc1490\&sektion=4) * NETGRAPH\_SOCKET --- [ng\_socket(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_socket\&sektion=4) * NETGRAPH\_SPLIT --- [ng\_split(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_split\&sektion=4) * NETGRAPH\_TAG --- [ng\_tag(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_tag\&sektion=4) * NETGRAPH\_TCPMSS --- [ng\_tcpmss(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_tcpmss\&sektion=4) * NETGRAPH\_TEE --- [ng\_tee(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_tee\&sektion=4) * NETGRAPH\_UI --- [ng\_UI(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_UI\&sektion=4) * NETGRAPH\_VJC --- [ng\_vjc(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_vjc\&sektion=4) * NETGRAPH\_VLAN --- [ng\_vlan(4)](https://man.freebsd.org/cgi/man.cgi?query=ng_vlan\&sektion=4) ```ini options VIMAGE options VNET_DEBUG # VIMAGE debug support ``` [vimage(9)](https://man.freebsd.org/cgi/man.cgi?query=vimage\&sektion=9) (an alias for VNET(9)), used for network stack virtualization. ### Network Interfaces Network interface devices provide the system with the ability to physically connect to networks. ```ini device loop ``` When networking is enabled, the [loop(4)](https://man.freebsd.org/cgi/man.cgi?query=loop\&apropos=0\&sektion=4) device is **required**. ```ini device ether ``` The `ether` device provides generic code for handling Ethernet; it is **required** when configuring Ethernet device drivers. ```ini device vlan ``` The [vlan(4)](https://man.freebsd.org/cgi/man.cgi?query=vlan\&apropos=0\&sektion=4) device implements Ethernet frame VLAN tagging per IEEE 802.1Q. ```ini device vxlan ``` The [vxlan(4)](https://man.freebsd.org/cgi/man.cgi?query=vxlan\&apropos=0\&sektion=4) device implements VXLAN encapsulation of Ethernet frames in UDP packets per RFC 7348. ```ini device wlan options IEEE80211_DEBUG # Enable debug information options IEEE80211_DEBUG_REFCNT options IEEE80211_SUPPORT_MESH # Enable 802.11s D3.0 / Mesh support options IEEE80211_SUPPORT_TDMA # Enable TDMA ``` The [wlan(4)](https://man.freebsd.org/cgi/man.cgi?query=wlan\&apropos=0\&sektion=4) device provides generic code supporting 802.11 drivers, including host AP mode; the wi and ath drivers require `wlan`, and it will eventually become a requirement for all 802.11 drivers. ```ini device wlan_wep # Support WEP encryption protocol device wlan_tkip # Support TKIP encryption protocol device wlan_ccmp # Support AES-CCMP encryption protocol device wlan_gcmp # Support AES-GCMP encryption protocol ``` Optional devices, dependent on the 802.11 `wlan` module. ```ini device wlan_xauth ``` The `wlan_xauth` device provides support for external (i.e., user-space) authenticators for 802.11 drivers that depend on the `wlan` module and support 802.1x and/or WPA security protocols. ```ini device wlan_acl device wlan_amrr ``` * The `wlan_acl` device provides a MAC-based access control mechanism for 802.11 drivers operating in AP mode and using the `wlan` module. * The `wlan_amrr` device provides the AMRR transmit rate control algorithm. ```ini device bpf ``` The `bpf` device enables the Berkeley Packet Filter. Be aware of the relevant security and administrative implications when enabling this option. DHCP depends on this option. ```ini device netmap ``` The `netmap` device enables memory-mapped access to network devices from user space, achieving wire-speed packet capture and generation even at 10 Gbit/s rates. Requires device driver support. Supported drivers include ixgbe, ixl, iflib (providing igb and em), re, vtnet, cxgbe. ```ini device disc ``` The `disc` device implements a minimal network interface that discards all sent packets and never receives any packets, used for testing and performance benchmarking. ```ini device epair ``` The `epair` device implements a pair of virtual back-to-back connected Ethernet interfaces. ```ini device edsc ``` The `edsc` device implements a minimal Ethernet interface that discards all sent packets and receives no packets. ```ini device tuntap ``` The `tuntap` device implements user-space PPP, [nos-tun(8)](https://man.freebsd.org/cgi/man.cgi?query=nos-tun\&sektion=8), and pty-like virtual Ethernet interfaces. ```ini device gif device gre device me options XBONEHACK ``` * The `gif` device implements IPv6 over IPv4 tunneling, IPv4 over IPv6 tunneling, IPv4 over IPv4 tunneling, and IPv6 over IPv6 tunneling * The `gre` device implements GRE (Generic Routing Encapsulation) tunneling per RFC 2784 and RFC 2890 * The `me` device implements Minimal Encapsulation within IPv4 per RFC 2004 * The `XBONEHACK` option allows configuring the same address pair on multiple `gif` interfaces ```ini device stf ``` The `stf` device implements 6to4 encapsulation. ```ini device pf device pflog device pfsync ``` The PF packet filter consists of three devices: * The `pf` device provides **/dev/pf** and the firewall code itself. * The `pflog` device provides the `pflog0` interface for logging packets. * The `pfsync` device provides the `pfsync0` interface for firewall state table synchronization (over the network). ```ini device if_bridge ``` Bridged network interface. ```ini device carp ``` Common Address Redundancy Protocol (CARP). For more details see: carp(4)\[EB/OL]. \[2026-03-26]. . ```ini device enc ``` IPsec interface. ```ini device lagg ``` LAGG link aggregation interface. ```ini device wg ``` WireGuard interface. ```ini device dummymbuf ``` `dummymbuf` is a pfil hook for mbuf modification. ### Internet Protocol Suite The Internet Protocol Suite provides basic protocol support for network communication. ```ini options MROUTING # Multicast routing ① options IPFIREWALL # IP firewall ② options IPFIREWALL_VERBOSE # Enable logging to syslogd(8) ③ options IPFIREWALL_VERBOSE_LIMIT=100 # Limit log verbosity ④ options IPFIREWALL_DEFAULT_TO_ACCEPT # Allow all traffic by default ⑤ options IPFIREWALL_NAT # Provides support for IPFW kernel NAT, requires LIBALIAS options IPFIREWALL_NAT64 # Provides support for IPFW kernel NAT64 options IPFIREWALL_NPTV6 # Provides support for IPFW kernel NPTv6 options IPDIVERT # Divert sockets. Enables divert IP sockets, used for ipfw divert; if compiled into the kernel, depends on IPFIREWALL options IPFILTER # ipfilter support options IPFILTER_LOG # ipfilter logging options IPFILTER_LOOKUP # ipfilter pools options IPFILTER_DEFAULT_BLOCK # Block all packets by default options IPSTEALTH # Support for stealth forwarding (forward packets without modifying TTL), used to hide firewalls from tools like traceroute options PF_DEFAULT_TO_DROP # Drop all packets by default, making pf(4) default rules deny all traffic options TCP_BLACKBOX # Enable enhanced TCP event logging options TCP_HHOOK # Enable hhook(9) framework hooks for the TCP stack options SOCKET_HHOOK # Enable hhook(9) framework hooks for socket operations options ROUTE_MPATH # Provides multipath routing support ``` * ①: `MROUTING` enables kernel multicast packet forwarding, which can be used with mrouted and XORP. * ②: `IPFIREWALL` requires the `ipfw` program. * ③: `IPFIREWALL_VERBOSE` sends logged packets to the system log. * ④: `IPFIREWALL_VERBOSE_LIMIT` limits the number of log entries for matching rules. > **Warning**: > > IPFIREWALL default policy is `deny ip from any to any`. If no rules are added to allow access at boot time, it may result in being unable to remotely access the system. > > It is recommended to set `firewall_type` to `open` in the **/etc/rc.conf** file when first enabling this feature, and then refine firewall rules in the **/etc/rc.firewall** file after confirming the new kernel functionality works correctly. * ⑤: `IPFIREWALL_DEFAULT_TO_ACCEPT` makes the default rule (at boot) allow all traffic. Use with caution; if an attacker can compromise the firewall host, they may access protected machines. However, it may be suitable as a tool for filtering specific problems on demand. Changing the default policy to `allow` can prevent unresponsiveness when the kernel and **/sbin/ipfw** binary are out of sync. `IPFIREWALL_PMOD` enables protocol modification module support. Currently only supports TCP MSS modification. ```ini options MBUF_STRESS_TEST options MBUF_PROFILING ``` The `MBUF_STRESS_TEST` option enables various random failure or edge case tests related to mbuf functions. See: mbuf(9)\[EB/OL]. \[2026-03-26]. for a list of available test cases. `MBUF_PROFILING` enables code for analyzing system output mbuf chains and returns logarithmic histograms of monitored parameters (e.g., packet size, wasted space, and number of mbufs in the chain) through the corresponding interface. ```ini options ACCEPT_FILTER_DATA # Data connection accept filter options ACCEPT_FILTER_DNS # DNS request accept filter options ACCEPT_FILTER_HTTP # HTTP request accept filter options ACCEPT_FILTER_TLS # TLS handshake accept filter ``` These options are used to enable statically linked accept filters. ```ini options TCP_SIGNATURE # Support for RFC 2385 ``` `TCP_SIGNATURE` provides support for RFC 2385 (TCP-MD5) digests. These digests are carried via TCP option 19. This option is typically used to protect TCP sessions (e.g., BGP) in situations where IPsec cannot or should not be used. This feature can be enabled per socket via the TCP\_MD5SIG socket option. Enabling this feature requires `device crypto` and either `options IPSEC` or `options IPSEC_SUPPORT`. ```ini options DUMMYNET ``` DUMMYNET enables the bandwidth limiter “dummynet”. This feature also requires IPFIREWALL. See: dummynet(4)\[EB/OL]. \[2026-03-26]. and ipfw(8)\[EB/OL]. \[2026-03-26]. . When running DUMMYNET, HZ/kern.hz should be at least 1000 to ensure sufficiently timely responses. ```ini options DEBUGNET ``` The `DEBUGNET` option enables the basic debugging/network API during kernel panic. NETDUMP and NETGDB require `DEBUGNET`. ```ini options NETDUMP ``` The `NETDUMP` option enables [netdump(4)](https://man.freebsd.org/cgi/man.cgi?query=netdump\&sektion=4) client support in the kernel. It can send kernel dumps to a remote host during a kernel panic. ```ini options NETGDB ``` The `NETGDB` option enables [netgdb(4)](https://man.freebsd.org/cgi/man.cgi?query=netgdb\&sektion=4) support in the kernel. It can make a panicked kernel available as a GDB remote debugging target over the network. ## File Systems Only the root file system needs to be statically compiled or preloaded as a module; other file systems can be loaded automatically at mount time. However, some users prefer to statically compile other file systems as well. > **Note** > > The UNION filesystem previously had bugs and is now actively maintained, although some issues still need to be resolved. ```ini options FFS # Fast Filesystem, i.e., UFS options NFSCL # Network File System client (NFS client) ``` At least one of the above options must be selected. ```ini options AUTOFS # Automount file system options CD9660 # ISO 9660 file system options FDESCFS # File descriptor file system options FUSEFS # FUSEFS support module options MSDOSFS # MS DOS file system (FAT, FAT32) options NFSLOCKD # Network lock manager options NFSD # Network File System server options KGSSAPI # Kernel GSSAPI implementation options NULLFS # NULL file system options PROCFS # Process file system (requires PSEUDOFS) options PSEUDOFS # Pseudo file system framework options PSEUDOFS_TRACE # PSEUDOFS debugging support options SMBFS # SMB/CIFS file system options TMPFS # Efficient memory file system options UDF # Universal Disk Format options UNIONFS # Union file system ``` The above options are all optional. ```ini options NFS_ROOT ``` Support for using NFS as the root filesystem (root device). ```ini options SOFTUPDATES ``` Soft Updates improve filesystem performance and reduce the risk of data inconsistency due to sudden shutdowns. ```ini options UFS_EXTATTR # ① options UFS_EXTATTR_AUTOSTART # ② ``` UFS Extended Attributes allow additional data to be associated with files, used for ACLs, Capabilities, and MAC labels. See `src/sys/ufs/ufs/README.extattr` for more information. * ①: `UFS_EXTATTR`: Extended attributes allow additional arbitrary metadata to be associated with files and directories, which can be allocated and read from user space as well as operated on within the kernel; see extattrctl(8). * ②: If the option `UFS_EXTATTR_AUTOSTART` is defined, UFS will search for the `.attribute` subdirectory under the filesystem root during mount operations. If found, extended attribute support will be automatically enabled for that filesystem. See: ffs(7)\[EB/OL]. \[2026-03-26]. . ```ini options UFS_ACL ``` Support for Access Control Lists (ACLs) on UFS filesystems. The current ACL implementation depends on the underlying filesystem's extended attribute support (UFS\_EXTATTR). See `src/sys/ufs/ufs/README.acls` for more information. ```ini options UFS_DIRHASH ``` UFS Directory Hashing improves the speed of operations on very large directories at the cost of memory consumption. ```ini options UFS_GJOURNAL ``` UFS journaling support based on [gjournal(8)](https://man.freebsd.org/cgi/man.cgi?query=gjournal\&sektion=8). ```ini options MD_ROOT_SIZE=10 ``` Reserves space in the kernel for an md device-based root filesystem. The value defined here is the number of kilobytes (KB) reserved for the filesystem. This definition is now optional. * If not defined, the root filesystem passed via the `MFS_IMAGE` build option will be automatically embedded into the kernel at link time, and its actual size will occupy kernel space entirely. * If defined, the legacy kernel embedded filesystem method is used: a fixed space of `MD_ROOT_SIZE` kilobytes (KB) is first allocated in the kernel, and if the filesystem image passed via the `MFS_IMAGE` build option matches the size, it will be written into the reserved area using the `dd` command. ```ini options MD_ROOT ``` Configures the md device as a potential root device, supporting preloaded mfs\_root and md\_root type images. ```ini options MD_ROOT_READONLY ``` Enables write protection for the md root device to prevent it from being mounted writable. ```ini options MD_ROOT_MEM ``` Allows reading md images from external memory regions. ```ini options QUOTA # Enable disk quotas ``` Enabling this option enables disk quota support. ```ini options SUIDDIR ``` If the device is used solely as a file server for PC and MAC users (using Samba services), it is recommended to enable this option and set user directories on filesystems that support the `suiddir` mount option. This setting causes newly created files to automatically inherit the directory owner's permissions (similar to group permissions). > **Note** > > If these users are allowed to execute programs, there will be security risks, so please limit usage to pure file server environments (this can effectively avoid many administrative difficulties). Directories owned by the root user are not subject to this restriction, and the execute permission bit will be automatically cleared. > **Note** > > The directory must also have the suid permission bit set (see chmod(1) manual for details). Since PC users cannot view/set file ownership, permission conflicts often occur. After enabling this feature, the relevant filesystem will align with user intuition: “Since this is my directory, the files I create naturally belong to me,” thereby significantly reducing technical support requirements. ```ini options NFS_MINATTRTIMO=3 # VREG attribute cache timeout (seconds) options NFS_MAXATTRTIMO=60 options NFS_MINDIRATTRTIMO=30 # VDIR attribute cache timeout (seconds) options NFS_MAXDIRATTRTIMO=60 options NFS_DEBUG # Enable NFS debugging ``` Several NFS options. ```ini options EXT2FS ``` Provides support for the Linux EXT2 filesystem. Use this feature with extreme caution; the ext2 code often lags behind kernel updates and lacks sufficient testing, so mounting in read-write mode may be risky (even mounting in read-only mode may cause system crashes). ```ini device mem ``` System memory devices: **/dev/mem**, **/dev/kmem** ```ini device ksyms ``` Kernel symbol table device: **/dev/ksyms**. ```ini options CD9660_ICONV options MSDOSFS_ICONV options UDF_ICONV ``` Optional character encoding conversion support, requires `LIBICONV`. Each option requires its base filesystem and the `LIBICONV` library. ## POSIX P1003.1B POSIX P1003.1B is the real-time extension of the POSIX standard, providing features such as priority scheduling, semaphores, and message queues. ```ini options _KPOSIX_PRIORITY_SCHEDULING ``` The real-time extension `_KPOSIX_PRIORITY_SCHEDULING` added in the 1993 POSIX standard provides support for `_POSIX_PRIORITY_SCHEDULING`. ```ini options P1003_1B_SEMAPHORES ``` The `p1003_1b_semaphores` feature is still highly experimental; if issues arise, users need to assist with debugging. ```ini options P1003_1B_MQUEUE ``` POSIX message queues. ## Security Policy Parameters Security policy parameters provide kernel configuration options related to system security, including auditing, mandatory access control, and other features. ```ini options AUDIT ``` BSM auditing. ```ini options MAC options MAC_BIBA options MAC_BSDEXTENDED options MAC_DDB options MAC_DO options MAC_IFOFF options MAC_IPACL options MAC_LOMAC options MAC_MLS options MAC_NONE options MAC_NTPD options MAC_PARTITION options MAC_PORTACL options MAC_PRIORITY options MAC_SEEOTHERUIDS options MAC_STUB options MAC_TEST options MAC_VERIEXEC options MAC_VERIEXEC_SHA1 options MAC_VERIEXEC_SHA256 options MAC_VERIEXEC_SHA384 options MAC_VERIEXEC_SHA512 device mac_veriexec_parser ``` Mandatory Access Control (MAC). ```ini options CAPABILITIES # Fine-grained capability control for file descriptors options CAPABILITY_MODE # Sandbox environment (no access to global namespaces) ``` Capsicum technology. ## Clock Clock options are used to configure the kernel clock frequency and time synchronization related features. ```ini options HZ=100 ``` The operation granularity is controlled by the kernel option `HZ` (default frequency is 1000 Hz, i.e., a scheduling interval of 1 millisecond). Virtual machine guest systems typically use the value `100`. Lower values may reduce system overhead at the cost of scheduling precision, but the adaptive timer code can mitigate this overhead. ```ini options PPS_SYNC ``` Enables the kernel PLL to use external PPS signal functionality, operating under the supervision of \[x]ntpd(8). See the ntpd documentation for more information: ```ini options FFCLOCK ``` Enables support for generic feed-forward clock in the kernel. Feed-forward clock support is an alternative to the feedback-oriented ntpd/system clock approach and requires a feed-forward synchronization algorithm (e.g., RADclock). See: ## SCSI Devices SCSI (Small Computer System Interface) is a standard interface for connecting computers and external devices. ```ini envvar hint.scbus.0.at="ahc0" envvar hint.scbus.1.at="ahc1" envvar hint.scbus.1.bus="0" envvar hint.scbus.3.at="ahc2" envvar hint.scbus.3.bus="0" envvar hint.scbus.2.at="ahc2" envvar hint.scbus.2.bus="1" envvar hint.da.0.at="scbus0" envvar hint.da.0.target="0" envvar hint.da.0.unit="0" envvar hint.da.1.at="scbus3" envvar hint.da.1.target="1" envvar hint.da.2.at="scbus2" envvar hint.da.2.target="3" envvar hint.sa.1.at="scbus1" envvar hint.sa.1.target="6" ``` SCSI device configuration. The SCSI subsystem consists of SCSI core code, multiple high-level SCSI device “type” drivers, and low-level host adapter device drivers. Refer to the ISA and PCI device configuration sections below for the host adapter list. The system can fix SCSI device configurations to ensure that specific buses, targets, and LUNs always correspond to the same device unit. In earlier versions, device unit numbers were assigned in the order detected on the SCSI bus. This means that if a disk drive is removed, the file **/etc/fstab** may need to be rewritten; caution is also needed when adding new disks, as new devices may be probed earlier, changing the configuration of existing devices. The system maintains this legacy behavior by default. Device unit allocation will start from the first non-fixed unit of that device type. For example, if a disk is fixed as `da3`, the first non-fixed disk will be assigned as `da4`. The syntax for device fixing configuration is as described above. ```ini device scbus # SCSI core code device ch # SCSI media changer device da # SCSI direct access ("disk") and optical media ("WORM") devices device sa # SCSI tape device cd # SCSI read-only direct access ("CD-ROM") device ses # Enclosure services (SES and SAF-TE) device pt # SCSI processor device targ # SCSI target mode code device targbh # SCSI target mode black hole device device pass # CAM passthrough driver device sg # Linux SCSI passthrough device ctl # CAM Target Layer ``` Devices that do not explicitly specify a “unit” (SCSI logical unit number) will default to LUN 0. All SCSI devices will be allocated the appropriate number of units based on actual needs. * The ch driver is used to drive SCSI media changer (“jukebox”) devices. * The da driver is used to drive SCSI direct access (“disk”) and optical media (“WORM”) devices. * The sa driver is used to drive SCSI sequential access (“tape”) devices. * The cd driver is used to drive SCSI read-only direct access (“CD-ROM”) devices. * The ses driver is used to drive SCSI Enclosure Services (“ses”) and SAF-TE (“SCSI Accessed Fault-Tolerant Enclosure”) devices. * The `pt` driver is used to drive SCSI processor devices. * The `sg` driver provides a passthrough API compatible with the Linux SG driver, and can work with Linux emulators to run Linux SG applications. It can also run independently, providing source-level API compatibility for porting applications to FreeBSD. Target mode support is implemented in this section, but still requires corresponding support from the SIM (SCSI host adapter driver). * The `targ` driver provides target mode support in the form of a processor type device, whose purpose is to provide the minimal context environment needed to respond to inquiry commands. The **/usr/share/examples/scsi\_target** directory contains user application examples demonstrating how to implement support for the remaining commands. * The `targbh` driver provides target mode support specifically for responding to incoming commands for unassigned logical units. * The `pass` driver provides a passthrough API for accessing the CAM subsystem. ## CAM CAM, Common Access Method storage subsystem, see: cam(4)\[EB/OL]. \[2026-03-26]. . ### CAM Debugging The following are kernel configuration options related to CAM debugging. ```ini options CAMDEBUG ``` Enable and compile all debugging features. ```ini options CAM_DEBUG_COMPILE=-1 ``` Specify the debug level to compile into the kernel. ```ini options CAM_DEBUG_FLAGS=(CAM_DEBUG_INFO|CAM_DEBUG_PROBE|CAM_DEBUG_PERIPH) ``` Specify the debug level to enable at system boot. ```ini options CAM_DEBUG_BUS=-1 ``` Restrict debugging to the specified bus. ```ini options CAM_DEBUG_TARGET=-1 ``` Restrict debugging to the specified target. ```ini options CAM_DEBUG_LUN=-1 ``` Restrict debugging to the specified LUN. ```ini options CAM_DEBUG_DELAY=1 ``` Delay time (in microseconds) after printing each line of debug information. ```ini options CAM_MAX_HIGHPOWER=4 ``` Maximum number of high-power (START UNIT) commands executed concurrently. ```ini options SCSI_NO_SENSE_STRINGS ``` Defining this option disables sense description strings. ```ini options SCSI_NO_OP_STRINGS ``` Defining this option disables opcode description strings. ```ini options SCSI_DELAY=5000 # Use conservative delay for regular SCSI devices ``` `SCSI_DELAY`: The number of milliseconds to freeze the SIM (SCSI adapter) queue after a bus reset, and the number of milliseconds to freeze the device queue after a bus device reset. This value can be changed at boot time and runtime via the sysctl tunable `kern.cam.scsi_delay`. ```ini options CAM_IOSCHED_DYNAMIC ``` Enables dynamic decision-making in the I/O scheduler based on hints and the current performance of storage devices. ```ini options CAM_IO_STATS ``` Displays additional CAM device statistics via sysctl. ```ini options CAM_TEST_FAILURE ``` Enables the ability to simulate I/O failures. ### CAM CD-ROM Read-Only Direct Access ("CD-ROM") Devices The following are kernel configuration options related to CD-ROM devices. ```ini options CHANGER_MIN_BUSY_SECONDS=2 ``` Minimum guaranteed service time slice for changer LUNs. The compile-time default value for this variable is 2 seconds. It can be adjusted via the sysctl `kern.cam.cd.changer.min_busy_seconds`. ```ini options CHANGER_MAX_BUSY_SECONDS=10 ``` Maximum time slice per changer LUN, only effective when there is I/O waiting for other LUNs. The compile-time default value for this variable is 10 seconds. It can be adjusted via the sysctl `kern.cam.cd.changer.max_busy_seconds`. ### CAM Sequential Access ("Tape") Device Driver The following are kernel configuration options related to tape devices. ```ini options SA_IO_TIMEOUT=4 ``` Timeout for read/write/WFM operations, in minutes. ```ini options SA_SPACE_TIMEOUT=60 ``` Timeout for space operations, in minutes. ```ini options SA_REWIND_TIMEOUT=(2*60) ``` Timeout for rewind operations, in minutes. ```ini options SA_ERASE_TIMEOUT=(4*60) ``` Timeout for erase operations, in minutes. ```ini options SA_1FM_AT_EOD ``` Default for device models that only have a single file mark at the end of tape (EOT). ### CAM Processor Target (PT) Device The following are kernel configuration options related to processor target devices. ```ini options SCSI_PT_DEFAULT_TIMEOUT=60 ``` Timeout for CAM processor target (pt) devices (optional), in seconds. Default value is 60 seconds. ### SES Passthrough Access on Other Devices (e.g., Disks) The following are kernel configuration options related to SES passthrough access. ```ini options SES_ENABLE_PASSTHROUGH ``` Since many newer SCSI disks report themselves as having SES (SCSI Enclosure Services) capabilities, they may conflict with the SES device of the enclosure containing the disk when building the topology, this feature is typically disabled by default. ### iSCSI iSCSI is a protocol for accessing SCSI devices over network connections. ```ini device cfiscsi # CAM Target Layer iSCSI target frontend device iscsi # iSCSI initiator device iser # iSCSI RDMA Extensions (iSER) initiator ``` iSCSI allows access to SCSI peripherals over network connections (e.g., TCP/IP sockets). ## Miscellaneous Devices and Options The following are various miscellaneous devices and kernel configuration options. ```ini device pty ``` BSD-style compatible pseudo terminals (pty). ```ini device nmdm ``` Back-to-back tty devices. ```ini device md ``` Memory-based (allocated via malloc) disk device. ```ini device snp ``` Snoop device, used to monitor terminal devices such as pty, vty, etc. ```ini device ccd ``` Concatenated Disk driver. This driver's functionality has been superseded by gconcat(8) (disk concatenation), gstripe(8) (disk striping), gmirror(8) (disk mirroring), and graid(8) (software RAID) under the GEOM framework. New deployments are recommended to use the corresponding GEOM modules. ```ini device firmware ``` [firmware(9)](https://man.freebsd.org/cgi/man.cgi?query=firmware\&sektion=9) support, firmware image loading and management. ```ini options LIBICONV ``` Kernel-side iconv library, see: iconv(3)\[EB/OL]. \[2026-03-26]. . ```ini options MSGBUF_SIZE=40960 ``` Size of the kernel message buffer. Should be **N × pagesize (memory page size)**. ## Hardware Bus Configuration Hardware bus configuration is used to set up communication interfaces between the system and hardware devices. ```ini device pci options PCI_HP # PCIe native hot-plug options PCI_IOV # PCI SR-IOV support ``` PCI bus and its related options. ## Hardware Device Configuration For ISA buses, the required hints are listed. PCI, CardBus, and SD/MMC are self-identifying buses, so hints are not required. ### Required Devices The following are basic device configuration options required for system operation. ```ini options KBD_DISABLE_KEYMAP_LOAD # Deny loading of keyboard layouts options KBD_INSTALL_CDEV # Generate CDEV entries in /dev ``` These options also apply to other keyboard drivers. ```ini options KBD_DELAY1=200 # Define initial key delay options KBD_DELAY2=15 # Define key repeat delay ``` Define keyboard delay parameters (for a responsive interactive console, try `200` and `15`). ```ini device kbdmux # Keyboard multiplexer options KBDMUX_DFLT_KEYMAP # Specify built-in keyboard layout makeoptions KBDMUX_DFLT_KEYMAP=it.iso # Set default keyboard layout to Italian ISO ``` ```ini options FB_DEBUG ``` Framebuffer debugging. ```ini options TEKEN_CONS25 # cons25 style terminal emulation options TEKEN_UTF8 # UTF-8 output processing ``` Enable experimental feature support for the syscons terminal emulator (teken). ```ini device vt options VT_ALT_TO_ESC_HACK=1 # Add ESC sequence before ALT key options VT_MAXWINDOWS=16 # Number of virtual consoles options VT_TWOBUTTON_MOUSE # Use right button to paste ``` vt video console driver. ```ini options VT_FB_MAX_HEIGHT=480 # Height options VT_FB_MAX_WIDTH=640 # Width ``` The above options are used to set the maximum framebuffer size. ```ini options TERMINAL_NORM_ATTR=(FG_GREEN|BG_BLACK) # Set normal terminal text color: foreground green, background black options TERMINAL_KERN_ATTR=(FG_LIGHTRED|BG_BLACK) # Set kernel message text color: foreground light red, background black ``` The above options are used to customize the default vt terminal colors. ### Optional Devices The following are various optional hardware device driver configuration options. #### SCSI Host Adapters ```ini device aacraid ``` PMC Adaptec RAID controllers, supporting 6th, 7th, 8th generation and later models. This driver uses the CAM container interface. ```ini device ahc ``` Adaptec 274x, 284x, 2910, 293x, 294x, 394x, 3950x, 3960x, 398x, 4944, 19160x, 29160x, and aic7770/aic78xx series. ```ini device ahd ``` Adaptec 29320/39320 controllers ```ini device isp ``` * Qlogic ISP 1020, 1040, and 1040B PCI SCSI host adapters * ISP 1240 Dual Ultra SCSI, ISP 1080 and 1280 (Dual) Ultra2 * ISP 12160 Ultra3 SCSI * Qlogic ISP 2100 and ISP 2200 1Gb Fibre Channel host adapters * Qlogic ISP 2300 and ISP 2312 2Gb Fibre Channel host adapters * Qlogic ISP 2322 and ISP 6322 2Gb Fibre Channel host adapters ```ini envvar hint.isp.0.disable="1" envvar hint.isp.0.role="3" envvar hint.isp.0.prefer_iomap="1" envvar hint.isp.0.prefer_memmap="1" envvar hint.isp.0.fwload_disable="1" envvar hint.isp.0.ignore_nvram="1" envvar hint.isp.0.fullduplex="1" envvar hint.isp.0.topology="lport" envvar hint.isp.0.topology="nport" envvar hint.isp.0.topology="lport-only" envvar hint.isp.0.topology="nport-only" ``` Description of isp-related hint parameters. ```ini envvar hint.isp.0.portwnn="w50000000aaaa0000" envvar hint.isp.0.nodewnn="w50000000aaaa0001" ``` isp-related hints. This workaround is adopted because values of type `u_int64_t` cannot be obtained and strings starting with `0x` cannot be parsed. ```ini device ispfw ``` Firmware module for Qlogic host adapters. ```ini #device mpi3mr ``` Broadcom MPIMR 3.0 IT/IR 24Gb/s SAS Tri-Mode RAID controller (aarch64 and amd64 only). ```ini device mpr ``` 3rd generation LSI-Logic MPT/Fusion (aarch64 and amd64 only). ```ini device mps ``` 2nd generation LSI-Logic MPT/Fusion (aarch64 and amd64 only). ```ini device mpt ``` LSI-Logic MPT/Fusion 53c1020, 53c1030 Ultra4, FC9x9 Fibre Channel host adapters. ```ini device sym ``` Symbios/Logic 53C8XX series PCI-SCSI I/O processors (aarch64 and amd64 only): * 53C810 * 53C810A * 53C815 * 53C825 * 53C825A * 53C860 * 53C875 * 53C876 * 53C885 * 53C895 * 53C895A * 53C896 * 53C897 * 53C1510D * 53C1010-33 * 53C1010-66 ```ini options AHC_ALLOW_MEMIO ``` Only when this option is set will the aic7xxx driver attempt to use memory-mapped I/O for all PCI controllers configured with memory-mapped I/O. However, this method does not work correctly on some motherboards, so it cannot be the default setting. ```ini options AHC_DUMP_EEPROM ``` Dump the contents of the ahc controller configuration PROM. ```ini options AHC_TMODE_ENABLE ``` Enable the target mode operation unit bitmap for [ahc(4)](https://man.freebsd.org/cgi/man.cgi?query=ahc\&sektion=4). ```ini options AHC_DEBUG ``` Compile Aic7xxx debugging code. ```ini options AHC_DEBUG_OPTS ``` Aic7xxx driver debug options. See: sys/dev/aic7xxx/aic7xxx.h\[EB/OL]. \[2026-03-26]. . ```ini options AHC_REG_PRETTY_PRINT ``` Print register bit fields in debug output. Increases the driver size by approximately 128 KB. See: ahc(4)\[EB/OL]. \[2026-03-26]. . ```ini options AHD_DEBUG ``` Compile aic79xx debugging code. ```ini options AHD_DEBUG_OPTS=0xFFFFFFFF ``` Aic79xx driver debug options. Increases the driver size by approximately 215 KB. See: ahd(4)\[EB/OL]. \[2026-03-26]. . ```ini options AHD_REG_PRETTY_PRINT ``` Print readable register definitions when debugging. ```ini options AHD_TMODE_ENABLE ``` Enable the target mode operation unit bitmap for [ahd(4)](https://man.freebsd.org/cgi/man.cgi?query=ahd\&sektion=4). #### `dev/isp/` (Qlogic SCSI/FC Driver) Related The following are kernel configuration options related to the Qlogic ISP driver. ```ini options ISP_TARGET_MODE=1 ``` `ISP_TARGET_MODE` enables [isp(4)](https://man.freebsd.org/cgi/man.cgi?query=isp\&sektion=4) target mode operation. ```ini options ISP_DEFAULT_ROLES=0 ``` `ISP_DEFAULT_ROLES`: default roles. * none = 0 * target = 1 * initiator = 2 * both = 3 (currently not supported) ```ini # ISP_INTERNAL_TARGET (simple internal disk target for testing) ``` > **Note** > > This item appears as-is in the original text; it is uncertain whether it is an options entry. Readers should verify for themselves. ```ini #options SYM_SETUP_SCSI_DIFF ``` HVD support for 825A, 875, 885. Disabled: 0 (default); Enabled: 1. ```ini #options SYM_SETUP_PCI_PARITY ``` PCI parity check. Disabled: 0; Enabled: 1 (default). ```ini #options SYM_SETUP_MAX_LUN ``` Number of supported LUNs. Default: 8, range: 1-64. ```ini device ciss ``` Compaq “CISS” RAID controllers (Smart Array 5\*/6\* series). These controllers provide a SCSI-like interface and depend on the CAM infrastructure. ```ini device ida # Compaq Smart RAID device mlx # Mylex DAC960 device mfi # LSI MegaRAID SAS device mfip # LSI MegaRAID SAS passthrough, requires CAM options MFI_DEBUG device mrsas # LSI/Avago MegaRAID SAS/SATA, 6Gb/s and 12Gb/s ``` Compaq Smart RAID, Mylex DAC960, and AMI MegaRAID controllers. Only the relevant entries need to be added; the code automatically discovers and configures all controllers it supports. #### NVMe NVMe is an interface protocol designed specifically for flash storage. ```ini device nvme # PCIe NVMe host driver/host controller options NVME_USE_NVD=1 # Use nvd(4) instead of CAM's nda(4) driver device nvmf # NVMeoF host driver/NVMeoF host device nvmft # NVMeoF ctl(4) frontend / NVMeoF CAM Target Layer frontend device nvmf_tcp # NVMeoF TCP transport device nda # NVMe direct access device (i.e., disk) device nvd # Non-CAM NVMe disk driver. Exposes NVMe namespaces as disks, depends on nvme ``` #### Serial ATA (SATA) Host Controllers SATA is an interface standard for connecting storage devices. ```ini device ahci # AHCI-compliant SATA controllers ``` Compatible with Advanced Host Controller Interface (AHCI). ```ini device mvs ``` Marvell 88SX50XX/88SX60XX/88SX70XX/SoC SATA controllers. ```ini device siis ``` SiliconImage SiI3124/SiI3132/SiI3531 SATA controllers. ```ini device ada ``` ATA/SATA direct access devices (i.e., disks). The above drivers are all part of the [cam(4)](https://man.freebsd.org/cgi/man.cgi?query=cam\&sektion=4) subsystem. They replace the less feature-rich [ata(4)](https://man.freebsd.org/cgi/man.cgi?query=ata\&sektion=4) subsystem drivers and support the same hardware. *** ```ini device ata # Legacy ATA/SATA controller ``` The `ATA` driver supports all legacy ATA/ATAPI controllers, including PC Card devices. On modern hosts, simply adding the line `device ata` allows the system to discover all PCI and PC Card ATA/ATAPI devices. It is also possible to use the `atacore` driver and then select individual bus and chipset drivers by vendor. For example, to build a system that only supports VIA chipsets, you can omit the `ata` line and only include the `atacore`, `atapci`, and `atavia` drivers. ```ini #device atacore # ATA core functionality #device ataisa # ISA bus support #device atapci # PCI bus support; generic chipset support only ``` Modular ATA drivers. ```ini #device ataacard # ACARD #device ataacerlabs # Acer Labs Inc. (ALI) #device ataamd # Advanced Micro Devices (AMD) #device ataati # ATI #device atacenatek # Cenatek #device atacypress # Cypress #device atacyrix # Cyrix #device atahighpoint # HighPoint #device ataintel # Intel #device ataite # Integrated Technology Inc. (ITE) #device atajmicron # JMicron #device atamarvell # Marvell #device atamicron # Micron #device atanational # National #device atanetcell # NetCell #device atanvidia # nVidia #device atapromise # Promise #device ataserverworks # ServerWorks #device atasiliconimage # Silicon Image Inc. (SiI) (formerly CMD) #device atasis # Silicon Integrated Systems Corp. (SiS) #device atavia # VIA Technologies Inc. ``` PCI ATA chipsets. ```ini envvar hint.ata.0.at="isa" envvar hint.ata.0.port="0x1f0" envvar hint.ata.0.irq="14" envvar hint.ata.1.at="isa" envvar hint.ata.1.port="0x170" envvar hint.ata.1.irq="15" ``` For older non-PCI, non-PnP BIOS systems, these hint lines need to be added. #### Serial Interface (uart) The serial interface provides serial communication capability between the system and external devices. ```ini device uart ``` [uart(4)](https://man.freebsd.org/cgi/man.cgi?query=uart\&sektion=4) generic serial interface driver. ```ini options UART_PPS_ON_CTS # Use CTS instead of DCD to capture time pulses options UART_POLL_FREQ # Set polling frequency, used when hardware does not support interrupts (default 50 Hz) ``` [uart(4)](https://man.freebsd.org/cgi/man.cgi?query=uart\&sektion=4) driver options. ```ini envvar hint.uart.0.at="isa" ``` This hint should only be used for pure ISA devices; it is not needed in other cases and is strongly discouraged. ```ini envvar hint.uart.0.port="0x3f8" envvar hint.uart.0.flags="0x10" envvar hint.uart.0.baud="115200" ``` The above three hints: UART is a system device (e.g., console or debug port) and is only used when the platform has no other way to pass information to the kernel. The hint unit number (i.e., `0`) is only used to group hints together and is unrelated to the unit number of the probed UART. `flags` is used for serial drivers that support consoles, such as [uart(4)](https://man.freebsd.org/cgi/man.cgi?query=uart\&sektion=4): * 0x10: Enable console support for this unit. Other console flags (if applicable) are ignored when this flag is not set. Enabling console support does not mean the unit is the preferred console. It can be enabled by using `-h` at boot, or by setting `boot_serial=YES` in the loader. Currently, at most one unit can have console support enabled; the first unit in the configuration file with this flag set is preferred. * `0x80`: Use this port for serial line gdb support in ddb, also known as the debug port. ```ini options BREAK_TO_DEBUGGER ``` Options for serial drivers supporting consoles: `BREAK_TO_DEBUGGER`: BREAK/DBG on the console will enter ddb (if available) ```ini options ALT_BREAK_TO_DEBUGGER ``` Solaris implemented a new BREAK, triggered by the character sequence `CR ~ ^b` (press **Enter**, then `~`, then the shortcut **Ctrl** + **B**. Similar below), similar to the common pattern used on remote consoles on Sun servers. FreeBSD has supplemented this feature: `CR ~ ^p` triggers a forced panic, `CR ~ ^r` triggers a clean reboot. ```ini device scc ``` Serial communication controller. Supports Freescale/NXP Quad Integrated and Zilog Z8530 multi-channel communication controllers. ```ini device puc ``` PCI generic communication driver. Supports various multi-port PCI I/O cards. #### Network Interfaces The following are configuration options for various network interface device drivers. **MII Bus** ```ini device mii # Minimal MII support device mii_bitbang # Generic module for bit-bang MII operations device miibus # MII support, with bit-bang and all PHYs ``` The MII bus is required for many PCI Ethernet cards, especially those using MII-compatible transceivers or implementing MII-like transceiver control interfaces. Adding `device miibus` to the kernel configuration introduces support for the generic miibus API, generic bit-bang support for MII, and all PHY drivers, including a generic driver for PHYs not specifically handled by an individual driver. If a NIC driver requires support for specific PHYs, this can be achieved by adding `device mii`, `device mii_bitbang`, and then the corresponding PHY drivers. ```ini device acphy # Altima Communications AC101 device amphy # AMD AM79c873 / Davicom DM910{1,2} device atphy # Attansic/Atheros F1 device axphy # Asix Semiconductor AX88x9x device bmtphy # Broadcom BCM5201/BCM5202 and 3Com 3c905C ``` ```ini device bnxt # Broadcom NetXtreme-C/NetXtreme-E ``` This driver is based on the generic MII bus controller code. `bnxt` supports Broadcom NetXtreme-C and NetXtreme-E PCIe 10/25/50G Ethernet adapters. ```ini device brgphy # Broadcom BCM54xx/57xx 1000baseTX device cgem # Cadence GEM Gigabit Ethernet device ciphy # Cicada/Vitesse CS/VSC8xxx device e1000phy # Marvell 88E1000 1000/100/10-BT device gentbi # Generic 10-bit 1000BASE-{LX,SX} fiber interface device icsphy # ICS ICS1889-1893 device ip1000phy # IC Plus IP1000A/IP1001 device jmphy # JMicron JMP211/JMP202 device lxtphy # Level One LXT-970 device nsgphy # NatSemi DP8361/DP83865/DP83891 device nsphy # NatSemi DP83840A device nsphyter # NatSemi DP83843/DP83815 device pnaphy # HomePNA device qsphy # Quality Semiconductor QS6612 device rdcphy # RDC Semiconductor R6040 device rgephy # Realtek 8169S/8110S/8211B/8211C device rlphy # Realtek 8139 device rlswitch # Realtek 8305 device smcphy # SMSC LAN91C111 device tdkphy # TDK 89Q2120 device truephy # LSI TruePHY device xmphy # XaQti XMAC II ``` **PCI Ethernet Cards Based on Generic MII Bus Controller Code** > **Tip** > > `bxe` Broadcom NetXtreme II (BCM5771X/BCM578XX) PCIe 10Gb Ethernet adapter. Entry located in `sys/x86/conf/NOTES`. This PCI Ethernet card is based on the generic MII bus controller code. ```ini device ae # Attansic/Atheros L2 Fast Ethernet ``` Supports 10/100Mbps Fast Ethernet adapters based on Attansic/Atheros L2 PCI-Express FastEthernet controllers. ```ini device age # Attansic/Atheros L1 Gigabit Ethernet ``` Supports Gigabit Ethernet adapters based on Attansic/Atheros L1 PCIe Gigabit Ethernet controllers. ```ini device alc # Atheros AR8131/AR8132 Ethernet ``` Supports Atheros AR8131/AR8132 PCIe Ethernet controllers. ```ini device ale # Atheros AR8121/AR8113/AR8114 Ethernet ``` Supports Atheros AR8121/AR8113/AR8114 PCIe Ethernet controllers. > **Note** > > `ath` Atheros a/b/g wireless cards (requires `ath_hal` and `wlan`). This entry is located elsewhere. ```ini device bce # Broadcom BCM5706/BCM5708 Gigabit Ethernet ``` Broadcom NetXtreme II (BCM5706/BCM5708) PCI/PCIe Gigabit Ethernet adapters. ```ini device bfe # Broadcom BCM440x 10/100 Ethernet ``` Broadcom BCM4401 Ethernet adapter. ```ini device bge # Broadcom BCM570xx Gigabit Ethernet ``` Supports Gigabit Ethernet adapters based on Broadcom BCM570x series controllers, including 3Com 3c996-T, Netgear GA302T, SysKonnect SK-9D21 and SK-9D41, as well as embedded Gigabit NICs on Dell PowerEdge 2550 servers. ```ini device cas # Sun Cassini/Cassini+ and NS DP83065 Saturn ``` Sun Cassini/Cassini+ and National Semiconductor DP83065 Saturn. ```ini device dc # DEC/Intel 21143 and various similar models ``` Supports PCI Fast Ethernet adapters based on DEC/Intel 21143 and similar chips, including ADMtek AL981 Comet, AN985 Centaur, ASIX AX88140A/AX88141, Davicom DM9100/DM9102, Lite-On 82c168/82c169, Lite-On/Macronix LC82C115 PNIC II, and Macronix 98713/98713A/98715/98715A/98725 PMAC. Replaces the old al, ax, dm, pn, and mx drivers. Examples of supported brands: Digital DE500-BA, Kingston KNE100TX, D-Link DFE-570TX, etc. ```ini device et # Agere ET1310 10/100/Gigabit Ethernet ``` ```ini device fxp # Intel EtherExpress PRO/100B (82557, 82558) envvar hint.fxp.0.prefer_iomap="0" ``` Intel EtherExpress Pro/100B (I/O access can be selected instead of memory mapping via the prefer\_iomap environment variable). ```ini device gem # Apple GMAC/Sun ERI/Sun GEM ``` Apple GMAC/Sun ERI/Sun GEM. ```ini device jme # JMicron JMC250 Gigabit/JMC260 Fast Ethernet ``` JMicron JMC260 Fast Ethernet/JMC250 Gigabit Ethernet adapters. ```ini device lge # Level 1 LXT1001 Gigabit Ethernet ``` Supports PCI Gigabit Ethernet adapters based on the Level 1 LXT1001 NetCellerator chip, including D-Link DGE-500SX, SMC TigerCard 1000 (SMC9462SX), and some Addtron cards. ```ini device lio # Marvell 23XX Ethernet adapter support ``` `lio`: supports Marvell 23XX series Ethernet adapters. ```ini device mlxfw # Mellanox firmware update module ``` `mlxfw`: Mellanox firmware update module. ```ini device mlx5 # IB and Ethernet shared code module ``` Mellanox ConnectX-4 and ConnectX-4 LX IB and Ethernet shared code module. ```ini device mlx5en # Mellanox ConnectX-4 and ConnectX-4 LX ``` Mellanox ConnectX-4 and ConnectX-4 LX PCIe Ethernet adapters. ```ini device msk # Marvell/SysKonnect Yukon II Gigabit Ethernet ``` msk: Supports PCI Gigabit Ethernet adapters based on Marvell/SysKonnect Yukon II Gigabit controllers, including 88E8021, 88E8022, 88E8061, 88E8062, 88E8035, 88E8036, 88E8038, 88E8050, 88E8052, 88E8053, 88E8055, 88E8056, and D-Link 560T/550SX. ```ini device my ``` Myson Fast Ethernet (MTD80X, MTD89X). ```ini device nge # NatSemi DP83820 Gigabit Ethernet ``` Supports PCI Gigabit Ethernet adapters based on the National Semiconductor DP83820/DP83821 chip, including SMC EZ Card 1000 (SMC9462TX), D-Link DGE-500T, Asante FriendlyNet GigaNIX 1000TA/1000TPC, Addtron AEG320T, Surecom EP-320G-TX, and Netgear GA622T. ```ini device re # Realtek 8139C+/8169/8169S/8110S ``` Realtek 8139C+/8169/8169S/8110S/8101E PCI/PCIe Ethernet adapters. ```ini device rl # Realtek 8129/8139 ``` Supports PCI Fast Ethernet adapters based on the Realtek 8129/8139 chip. Since memory-mapped mode can cause serious lockups on SMP hardware, this driver defaults to using programmed I/O to access registers. This driver also supports the Accton EN1207D “Cheetah” card, using the MPX 5030/5038 chip (Realtek or its clone). The D-Link DFE-530TX+ uses a Realtek chip and should use this driver, not the `vr` driver. ```ini device sge # Silicon Integrated Systems SiS190/191 ``` Silicon Integrated Systems SiS190/191 Fast/Gigabit Ethernet adapters. ```ini device sis # Silicon Integrated Systems SiS 900/SiS 7016 ``` Supports NICs based on Silicon Integrated Systems SiS 900/SiS 7016 and NS DP83815 PCI Fast Ethernet controller chips. ```ini device sk # SysKonnect SK-984x & SK-982x Gigabit Ethernet ``` Supports SysKonnect SK-984x series PCI Gigabit Ethernet adapters, including SK-9841/9842 single-port (single-mode/multi-mode fiber) and SK-9843/9844 dual-port (single-mode/multi-mode). The driver automatically detects the number of card ports and treats each port as an independent network interface. ```ini device ste # Sundance ST201 (D-Link DFE-550TX) ``` Sundance ST201 PCI Fast Ethernet controller, including D-Link DFE-550TX. ```ini device stge # Sundance/Tamarack TC9021 Gigabit Ethernet ``` Supports Gigabit Ethernet adapters based on Sundance/Tamarack TC9021 series controllers, including Sundance ST2021/ST2023, Sundance/Tamarack TC9021, D-Link DL-4000, and ASUS NX1101. ```ini device vr # VIA Rhine, Rhine II ``` Supports various Fast Ethernet adapters based on VIA VT3043 “Rhine I” and VT86C100A “Rhine II” chips. Includes D-Link DFE520TX, DFE530TX (DFE530TX+ uses the rl driver), Hawking PN102TX, and AOpen/Acer ALN-320. ```ini device vte # DM&P Vortex86 RDC R6040 Fast Ethernet ``` DM\&P Vortex86 RDC R6040 Fast Ethernet. ```ini device xl # 3Com 3c90x ("Boomerang", "Cyclone") ``` Supports 3Com 3c900, 3c905, 3c905B, and 3c905C (Fast) Etherlink XL NICs and integrated controllers, including the 3c905B-TX chip on some Dell Optiplex and Dell Precision desktops, and the 3c905-TX chip on Dell Latitude laptop docking stations. Also supports 3Com 3c980(C)-TX, 3Com 3cSOHO100-TX, 3Com 3c450-TX. **PCI/PCI-X/PCIe Ethernet Cards Using the iflib Framework** ```ini device iflib ``` [iflib](https://man.freebsd.org/cgi/man.cgi?query=iflib\&sektion=9) network interface driver framework. ```ini device em # Intel Pro/1000 Gigabit Ethernet ``` Intel PRO/1000 Gigabit Ethernet 82542/82543/82544 series adapters. This NIC is based on the generic MII bus controller code. ```ini device ix # Intel Pro/10GbE PCIe Ethernet device ixv # Intel Pro/10GbE PCIe Ethernet VF ``` **PCI Ethernet Cards (Ethernet)** ```ini device cxgb # Chelsio T3 10 Gigabit Ethernet device cxgb_t3fw # Chelsio T3 10 Gigabit Ethernet firmware ``` 1 GbE / 10 GbE PCIe Ethernet adapters based on the Chelsio T3 chip. This NIC is based on the generic MII bus controller code. ```ini device cxgbe # Chelsio T4-T6 1/10/25/40/100 Gigabit Ethernet ``` Chelsio T4 / T5 / T6 series 1 / 10 / 25 / 40 / 100 GbE PCIe Ethernet adapters. This NIC is based on the generic MII bus controller code. ```ini device cxgbev # Chelsio T4-T6 Virtual Function ``` PCIe Virtual Functions based on Chelsio T4, T5, and T6. This NIC is based on the generic MII bus controller code. ```ini device le # AMD Am7900 LANCE and Am79C9xx PCnet ``` AMD Am7900 LANCE and Am79C9xx PCnet NICs. This NIC is based on the generic MII bus controller code. ```ini device mxge ``` Myricom Myri-10G 10 GbE Ethernet card. ```ini device oce # Emulex 10 GbE (OneConnect Ethernet) ``` Emulex 10 GbE adapter (OneConnect Ethernet). This NIC is based on the generic MII bus controller code. ```ini device ti # Alteon Networks Tigon I/II Gigabit Ethernet ``` Supports PCI Gigabit Ethernet adapters based on Alteon Tigon I / II chips, including Alteon AceNIC, 3Com 3C985, Netgear GA620, etc. It is recommended to significantly increase the value of `kern.ipc.nmbclusters` when using this driver. This NIC is based on the generic MII bus controller code. **PCI IEEE 802.11 Wireless Cards (Wi-Fi)** ```ini device ath # Atheros PCI/CardBus cards device ath_hal # PCI/CardBus chip support #device ath_ar5210 # AR5210 chip #device ath_ar5211 # AR5211 chip #device ath_ar5212 # AR5212 chip #device ath_rf2413 # AR2413 chip #device ath_rf2417 # AR2417 chip #device ath_rf2425 # AR2425 chip #device ath_rf5111 # AR5111 chip #device ath_rf5112 # AR5112 chip #device ath_rf5413 # AR5413 chip #device ath_ar5416 # AR5416 chip ``` Atheros series wireless cards. ```ini options AH_RXCFG_SDMAMW_4BYTES ``` All AR5212 chips have issues when used with AR71xx CPUs. These models have a bug that triggers a fatal bus error only on AR71xx. The specific details of the bug are not yet clear, but some information can be found on pages 4, 5, and 6 of the [relevant discussion thread](https://forum.openwrt.org/viewtopic.php?pid=70060) on the OpenWrt forum. Enabling this option applies the workaround. This workaround incurs a performance penalty, but without it, the device will not work at all. Normally, DMA transfers for this NIC use 128-byte bursts, but on affected CPUs, only 4-byte bursts are safe. ```ini #device ath_ar9160 # AR9160 chip #device ath_ar9280 # AR9280 chip #device ath_ar9285 # AR9285 chip device ath_rate_sample # SampleRate transmit rate control for ath ``` Atheros-related wireless cards. ```ini device bwi # Broadcom BCM430* BCM431* ``` Broadcom `BCM430*` and `BCM431*` series wireless cards. This NIC is based on the generic MII bus controller code. ```ini device bwn # Broadcom BCM43xx ``` Broadcom BCM43xx series wireless cards. This NIC is based on the generic MII bus controller code. ```ini device malo # Marvell Libertas wireless cards ``` This NIC is based on the generic MII bus controller code. ```ini device mwl # Marvell 88W8363 802.11n wireless cards device mwlfw # Marvell 88W8363 firmware ``` This NIC is based on the generic MII bus controller code. The `mwl` driver depends on the `mwlfw` firmware. ```ini device ral # Ralink Technology RT2500 wireless cards ``` Ralink Technology IEEE 802.11 wireless adapters. This NIC is based on the generic MII bus controller code. ```ini device rtwn # Realtek wireless cards/Realtek wireless adapters device rtwnfw # Realtek wireless firmware ``` This NIC is based on the generic MII bus controller code. ```ini #options TI_SF_BUF_JUMBO ``` Use the [sf\_buf(9)](https://man.freebsd.org/cgi/man.cgi?query=sf_buf\&sektion=9) interface to handle jumbo buffers on [ti(4)](https://man.freebsd.org/cgi/man.cgi?query=ti\&sektion=4) controllers. ```ini #options TI_JUMBO_HDRSPLIT ``` Enable the header splitting option for the [ti(4)](https://man.freebsd.org/cgi/man.cgi?query=ti\&sektion=4) driver firmware. This feature only applies to Tigon II chips and has no effect on Tigon I chips. This option depends on the `TI_SF_BUF_JUMBO` option above. ```ini options MCLSHIFT=12 # mbuf cluster shift size, 12 == 4 kB; default value is 11 == 2 kB options MSIZE=256 # mbuf size (bytes) ``` These two options are used to adjust the mbuf cluster size and mbuf size respectively. Since changing the default values may cause a mismatch between the mbuf size assumed by the kernel and the mbuf size assumed by modules, extreme caution must be exercised when changing their default values to other values when handling NIC driver modules. Currently, the only driver capable of detecting this mismatch is [ti(4)](https://man.freebsd.org/cgi/man.cgi?query=ti\&sektion=4). #### Audio Devices ```ini device sound ``` Generic audio driver. **`snd_*`: Device-Specific Drivers** ```ini device snd_als4000 ``` Avance Logic ALS4000 PCI. ```ini device snd_atiixp ``` ATI IXP 200/300/400 PCI. ```ini device snd_cmi ``` CMedia CMI8338/CMI8738 PCI. ```ini device snd_cs4281 ``` Crystal Semiconductor CS4281 PCI. ```ini device snd_csa ``` Crystal Semiconductor CS461x/428x PCI (excluding 4281). ```ini device snd_emu10k1 ``` Creative EMU10K1 PCI and EMU10K2 (Audigy) PCI. ```ini device snd_emu10kx ``` Creative SoundBlaster Live! and Audigy. ```ini device snd_envy24 ``` VIA Envy24 and compatible devices, depends on `snd_spicds`. ```ini device snd_envy24ht ``` VIA Envy24HT and compatible devices, depends on `snd_spicds`. ```ini device snd_es137x ``` Ensoniq AudioPCI ES137x PCI. ```ini device snd_fm801 ``` Forte Media FM801 PCI. ```ini device snd_hda ``` Intel High Definition Audio (controller) and compatible devices. ```ini device snd_hdsp ``` RME HDSP 9632 and HDSP 9652. ```ini device snd_hdspe ``` RME HDSPe AIO and RayDAT. ```ini device snd_ich ``` Intel ICH AC’97 and many more audio controllers integrated in chipsets, such as NVIDIA nForce controllers. ```ini device snd_maestro3 ``` ESS Technology Maestro-3/Allegro PCI. ```ini device snd_neomagic ``` Neomagic 256 AV/ZX PCI. ```ini device snd_solo ``` ESS Solo-1x PCI. ```ini device snd_spicds ``` SPI codec driver, required by Envy24/Envy24HT drivers. ```ini device snd_t4dwave ``` Trident 4DWave DX/NX PCI, SiS 7018 PCI, and Acer Labs M5451 PCI. ```ini device snd_uaudio ``` USB audio. ```ini device snd_via8233 ``` VIA VT8233x PCI. ```ini device snd_via82c686 ``` VIA VT82C686A PCI. ```ini device snd_vibes ``` S3 Sonicvibes PCI. **Hint Configuration for Non-PnP Sound Cards** The device flags can provide additional information to the driver, which is normally obtained automatically through the PnP interface. * bit 2..0: secondary DMA channel; * bit 4: set if the board uses two DMA channels; * bit 15..8: board type, used to override auto-detection; leave as `0` if unsure (currently not implemented). ```ini envvar hint.pcm.0.at="isa" envvar hint.pcm.0.irq="10" envvar hint.pcm.0.drq="1" envvar hint.pcm.0.flags="0x0" envvar hint.sbc.0.at="isa" envvar hint.sbc.0.port="0x220" envvar hint.sbc.0.irq="5" envvar hint.sbc.0.drq="1" envvar hint.sbc.0.flags="0x15" envvar hint.gusc.0.at="isa" envvar hint.gusc.0.port="0x220" envvar hint.gusc.0.irq="5" envvar hint.gusc.0.drq="1" envvar hint.gusc.0.flags="0x13" ``` **Debugging/Testing** ```ini options SND_DEBUG ``` Enables additional debugging code, including sanity checks and potentially increased verbosity. ```ini options SND_DIAGNOSTIC ``` `SND_DIAGNOSTIC` is similar to `INVARIANTS` / `DIAGNOSTIC`, tolerating no inconsistencies whatsoever. ```ini options SND_FEEDER_MULTIFORMAT ``` `SND_FEEDER_MULTIFORMAT` compiles only 16/32-bit feeders by default. This option enables most feeder format converters (excluding 8-bit). > **Warning** > > May result in increased kernel size. ```ini options SND_FEEDER_FULL_MULTIFORMAT ``` `SND_FEEDER_FULL_MULTIFORMAT` is the same as above (`SND_FEEDER_MULTIFORMAT`), but includes 8-bit feeders. ```ini options SND_FEEDER_RATE_HP ``` `SND_FEEDER_RATE_HP` (feeder\_rate) will use high-precision 64-bit arithmetic whenever possible (which is avoided by default). May cause decreased operation speed. ```ini options SND_PCM_64 ``` `SND_PCM_64` (i386/32-bit architecture only) processes 32-bit samples through 64-bit integers/arithmetic. May slightly improve dynamic range, but operation speed may slow down. ```ini options SND_OLDSTEREO ``` `SND_OLDSTEREO` only allows 2 channels, effectively disabling multi-channel processing. #### CardBus (PC Card Bus Interface, PC Card) ```ini device cbb ``` Implements PCI/CardBus bridges with the YENTA interface. ```ini device cardbus ``` CardBus slot. #### MMC/SD ```ini device mmc ``` MMC/SD bus, required for eMMC chips. ```ini device mmcsd ``` MMC/SD memory card. Required for eMMC chips. ```ini device sdhci ``` Generic PCI SD host controller. ```ini device rtsx ``` Realtek SD card reader (RTS5209, RTS5227, etc.). #### SMB Bus System Management Bus (System Management Bus) support is provided by the "smbus" device. Access SMBus through the `smb` device (**/dev/smb\***), which is a child of the `smbus` device. **Device Support** ```ini device smb ``` Standard I/O through **/dev/smb\***. **SMB Interface Support** ```ini device smbus ``` `smbus` bus support, dependent on the `smb` device above. ```ini device intpm ``` Intel PIIX4 (82371AB, 82443MX) power management unit. ```ini options ENABLE_ALART ``` Controls alarm on the Intel intpm driver. ```ini device alpm ``` Acer Aladdin-IV/V/Pro2 power management unit. ```ini device ichsmb ``` Intel ICH SMBus controller chips (82801AA, 82801AB, 82801BA). ```ini device viapm ``` VIA VT82C586B/596B/686A and VT8233 power management unit. ```ini device amdpm ``` AMD 756 power management unit. ```ini device amdsmb ``` AMD 8111 SMBus 2.0 controller. ```ini device nfpm ``` NVIDIA nForce power management unit. ```ini device nfsmb ``` NVIDIA nForce2/3/4 MCP SMBus 2.0 controller. ```ini device ismt ``` Intel SMBus 2.0 controller chip (for Atom S1200, C2000) **SMBus Peripheral Devices** ```ini device jedec_dimm ``` Provides asset information and temperature reporting for DDR3 and DDR4 DIMMs. #### I²C Bus I²C bus support is provided by the `iicbus` device. ```ini device iicbus ``` Provides I²C bus support; devices below such as `ic`, `iic`, `iicsmb` all depend on this device. **Supported Devices** ```ini device ic ``` I²C network interface, depends on `iicbus`. ```ini device iic ``` I²C standard I/O interface, depends on `iicbus`. Access I²C slave devices from userspace via [ioctl(2)](https://man.freebsd.org/cgi/man.cgi?query=ioctl\&sektion=2). ```ini device iicsmb ``` SMB bridged via I²C (I²C to SMB bridge using any `iicbus` interface). Allows I²C I/O through SMB commands, depends on `iicbus`. ```ini device iicoc ``` OpenCores I²C controller support. Simple polling driver for the OpenCores I²C controller. **Others** ```ini device iicbb ``` Bitbang driver, implements I²C on a pair of GPIO pins. Provides generic I²C bit-banging code (required by `lpbb`). **I²C Bus Multiplexer (mux) Devices** ```ini device iicmux ``` I²C multiplexer core driver. ```ini device iic_gpiomux ``` I²C multiplexer hardware controlled via GPIO pins. ```ini device ltc430x ``` LTC4305 and LTC4306 I²C multiplexer chips. **I²C Peripheral Devices** ```ini device ad7418 ``` Analog Devices temperature and voltage sensor driver. ```ini device ads111x ``` Texas Instruments ADS101x and ADS111x ADC. ```ini device ds1307 ``` Dallas DS1307 RTC and compatible chips. ```ini device ds13rtc ``` All Dallas/Maxim ds13xx series chips. ```ini device ds1672 ``` Dallas DS1672 RTC. ```ini device ds3231 ``` Dallas DS3231 RTC and temperature sensor. ```ini device fan53555 ``` Fairchild Semiconductor FAN53555/SYR82x regulator. ```ini device icee ``` AT24Cxxx and compatible EEPROM. ```ini device isl12xx ``` Intersil ISL12xx RTC. ```ini device lm75 ``` LM75 compatible temperature sensor. ```ini device nxprtc ``` NXP RTC: PCA/PFC212x, PCA/PCF85xx series. ```ini device rtc8583 ``` Epson RTC-8583. ```ini device s35390a ``` Seiko Instruments S-35390A RTC. ```ini device sy8106a ``` Silergy SY8106A buck regulator. #### Parallel Bus Interface The parallel bus interface is driven by the `ppbus` device. Multiple devices can be connected to the parallel interface simultaneously, and they can be automatically probed and attached when detected. **Supported Interfaces** ```ini device ppc ``` ISA bus parallel port interface. **Supported Devices** ```ini options PPC_PROBE_CHIPSET ``` Enables chipset-specific detection (see flags in ppc(4)). ```ini options DEBUG_1284 ``` IEEE1284 signal protocol debugging. ```ini options PERIPH_1284 ``` Enables the computer to act as an IEEE 1284 compliant peripheral. ```ini options DONTPROBE_1284 ``` Avoid probing PnP parallel devices at boot. ```ini options LPT_DEBUG ``` Printer driver debugging. ```ini options PPC_DEBUG ``` Parallel chipset level debugging. ```ini options PLIP_DEBUG ``` Parallel network IP interface debugging. ```ini options PCFCLOCK_VERBOSE ``` `pcfclock` driver verbose output. ```ini options PCFCLOCK_MAX_RETRIES=5 ``` Maximum read attempts (default 10). ```ini envvar hint.ppc.0.at="isa" envvar hint.ppc.0.irq="7" device ppbus ``` ```ini device lpt ``` Parallel printer. ```ini device plip ``` Parallel network interface. ```ini device ppi ``` General-purpose I/O (“Geek Port”) and IEEE 1284 I/O. ```ini device pps ``` Pulse per second timing interface. ```ini device lpbb ``` Philips official parallel port I²C bit-banging interface. ```ini device pcfclock ``` Parallel port clock driver. #### General Purpose I/O Pins (GPIO) ```ini device dwgpio ``` Synopsys DesignWare APB GPIO controller. ```ini device gpio ``` GPIO interface and bus support. ```ini device gpiobacklight ``` sysctl-controlled backlight, based on GPIO. ```ini device gpioiic ``` I²C via GPIO bitbang. ```ini device gpiokeys ``` [kbd(4)](https://man.freebsd.org/cgi/man.cgi?query=kbd\&sektion=4\&n=1) linkage layer for GPIO key input. ```ini device gpioled ``` [LED(4)](https://man.freebsd.org/cgi/man.cgi?query=led\&sektion=4) GPIO linkage layer. ```ini device gpiopower ``` GPIO power-off event handler. ```ini device gpiopps ``` Pulse per second input from GPIO pins. ```ini device gpioregulator ``` extres/regulator linkage layer interface for GPIO pins. ```ini device gpiospi ``` SPI via GPIO bitbang. ```ini device gpioths ``` 1-Wire (one-wire protocol) temperature and humidity sensor based on GPIO pins. #### Pulse Width Modulation (PWM) ```ini device pwmbus ``` PWM interface and bus support. ```ini device pwmc ``` User-space control access to PWM outputs. #### Etherswitch Framework and Drivers ```ini device etherswitch ``` [etherswitch(4)](https://man.freebsd.org/cgi/man.cgi?query=etherswitch\&sektion=4) Ethernet switch framework. ```ini device miiproxy ``` [miibus(4)](https://man.freebsd.org/cgi/man.cgi?query=miibus\&sektion=4) MII bus function proxy device. ```ini device arswitch ``` Atheros switch. ```ini device ip17x ``` IC+ 17x series switch. ```ini device rtl8366rb ``` Realtek RTL8366 switch. ```ini device ukswitch ``` Multi-PHY switch. #### Kernel BOOTP Support ```ini options BOOTP ``` Use BOOTP to obtain IP address and hostname. ```ini options BOOTP_NFSROOT ``` Mount NFS root filesystem via BOOTP information, depends on NFSCL and NFS\_ROOT. ```ini options BOOTP_NFSV3 ``` Use NFS v3 protocol to mount NFS root. ```ini options BOOTP_COMPAT ``` Workaround for compatibility with buggy bootp daemons. ```ini options BOOTP_WIRED_TO=fxp0 ``` Specify the fxp0 network interface to run BOOTP. ```ini options BOOTP_BLOCKSIZE=8192 ``` Overwrite NFS block size to 8192. ```ini options SW_WATCHDOG ``` Enable software watchdog routines even if a hardware watchdog is present. By default, the software watchdog timer is only enabled when no hardware watchdog is present. ```ini options DEADLKRES ``` Add a software deadlock resolver thread. ```ini options NSFBUFS=1024 ``` Sets the number of `sf_buf` to allocate. `sf_buf` are virtual buffers used by sendfile(2) for mapping file virtual memory pages; the default count is approximately 16\*MAXUSERS+512. Typically, each concurrent file transfer requires about 4 such buffers. ```ini options DEBUG_LOCKS ``` Enables additional debugging code for the lock mechanism. This feature stores filename and line number information of lock acquisitions in the lock structure and modifies several function calls to pass relevant data. This feature has no practical use unless debugging lock-related code. > **Note** > > This option modifies the Kernel Binary Interface (KBI) and requires recompilation of all kernel modules. #### VirtIO virtio entries provide a generic bus for device drivers to use. This bus must be used in conjunction with an interface for communicating with the host. The VirtIO specification defines several such interfaces, including PCI and MMIO interfaces. ```ini device virtio ``` Generic VirtIO bus (must be enabled). ```ini device virtio_mmio ``` VirtIO MMIO interface. ```ini device virtio_pci ``` VirtIO PCI interface. ```ini device vtnet ``` VirtIO Ethernet device. ```ini device virtio_balloon ``` VirtIO Memory Balloon device. ```ini device virtio_blk ``` VirtIO block device. ```ini device virtio_console ``` VirtIO console device. ```ini device virtio_gpu ``` VirtIO GPU device. ```ini device virtio_random ``` VirtIO random number (entropy) device. ```ini device virtio_scmi ``` VirtIO SCMI (System Control and Management Interface) device. ```ini device virtio_scsi ``` VirtIO SCSI device. #### HID (Human Interface Device) Support ```ini device hid ``` Generic HID support. ```ini options HID_DEBUG ``` Enable debug information. ```ini device hidbus ``` HID bus. ```ini device hidmap ``` HID to evdev mapping. ```ini device hidraw ``` Raw device access driver. ```ini options HIDRAW_MAKE_UHID_ALIAS ``` Install alias **/dev/uhid** for **/dev/hidraw**. ```ini device hconf ``` Multi-touch configuration table. ```ini device hcons ``` Consumer control device. ```ini device hgame ``` Generic game controller. ```ini device hkbd ``` HID keyboard. ```ini device hms ``` HID mouse. ```ini device hmt ``` HID multi-touch device (Microsoft standard compatible). ```ini device hpen ``` Generic stylus driver. ```ini device hsctrl ``` System control. ```ini device ps4dshock ``` Sony PS4 DualShock 4 gamepad driver. ```ini device u2f ``` FIDO/U2F authentication device. ```ini options U2F_DROP_UHID_ALIAS ``` Do not install alias **/dev/uhid** for **/dev/u2f**, and change the driver name from `uhid` to `u2f`. ```ini device xb360gp ``` Xbox 360 gamepad driver. ### USB Support ```ini device uhci ``` UHCI controller. ```ini device ohci ``` OHCI controller. ```ini device ehci ``` EHCI controller. ```ini device xhci ``` xHCI controller. ```ini #device slhci ``` SL811 controller. ```ini device usb ``` Generic USB framework (required for USB). ```ini device udbp ``` USB double bulk pipe driver. ```ini device ugold ``` USB thermometer. ```ini device uled ``` USB LED light. ```ini device uhid ``` HID human interface device (for other devices with buttons and dials). ```ini device ukbd ``` USB keyboard. ```ini device ulpt ``` USB printer. ```ini device umass ``` USB mass storage device driver (depends on `scbus` and `da` devices). ```ini device usfs ``` USB mass storage driver in device-side mode. ```ini device umct ``` USB support for Belkin F5U109 and Magic Control Technology serial adapters. ```ini device umodem ``` USB modem. ```ini device ums ``` USB mouse. ```ini device atp # Apple Touchpad driver device wsp # Wellspring touchpad, for Apple laptops ``` USB touchpad. ```ini device uep ``` eGalax USB touchscreen. ```ini device urio ``` Diamond Rio 500 MP3 player. ```ini device usbhid ``` HID-over-USB driver. #### USB Serial Ports ```ini device ucom ``` USB serial port support. ```ini device u3g ``` USB support for Option, Novatel, Huawei, and Sierra 3G modem cards. ```ini device uark ``` USB support for serial adapters based on the Technologies ARK3116 chip. ```ini device ubsa ``` USB support for Belkin F5U103 and compatible serial adapters. ```ini device uftdi ``` USB support for serial adapters based on the FT8U100AX and FT8U232AM chips. ```ini device uipaq ``` USB support for certain Windows CE-based serial communication devices. ```ini device uplcom ``` USB support for Prolific PL-2303 serial adapters. ```ini device uslcom ``` USB support for serial adapters based on Silicon Laboratories CP2101/CP2102 chips. ```ini device uvisor ``` USB Visor and Palm device support. ```ini device uvscom ``` USB serial support for DDI Pocket PHS devices. #### USB Ethernet ```ini device uether ``` USB Ethernet support. ```ini device aue ``` ADMtek USB Ethernet device. Supports LinkSys USB100TX, Billionton USB100, Melco LU-ATX, D-Link DSB-650TX, and SMC 2202USB. Also compatible with the ADMtek AN986 Pegasus evaluation board. ```ini device axe ``` ASIX Electronics AX88172 USB 2.0 Ethernet driver. Used for LinkSys USB200M and various other adapters. ```ini device axge ``` ASIX Electronics AX88178A/AX88179 USB 2.0/3.0 Gigabit Ethernet driver. ```ini device cdce ``` Devices using USB-based Ethernet communication, specifically those conforming to the Communication Device Class (CDC) Ethernet specification. Supports Sharp Zaurus PDAs, certain DOCSIS cable modems, mobile phones, and other devices. ```ini device cue ``` CATC USB-EL1201A USB Ethernet device. Supports CATC Netmate and Netmate II, as well as Belkin F5U111. ```ini device kue ``` Kawasaki LSI Ethernet device. Supports the following adapters: * LinkSys USB10T * Entrega USB-NET-E45 * Peracom Ethernet adapter * 3Com 3c19250 * ADS Technologies USB-10BT * ATen UC10T * Netgear EA101 * D-Link DSB-650 * SMC 2102USB and 2104USB * Corega USB-T ```ini device rue ``` Realtek RTL8150 USB to Fast Ethernet device. Supports Melco LUA-KTX and GREEN HOUSE GH-USB100B. ```ini device udav ``` Davicom DM9601E USB to Fast Ethernet device. Supports Corega FEther USB-TXC. ```ini device ure ``` Realtek RTL8152/RTL8153 USB Ethernet driver. ```ini device mos ``` Moschip MCS7730/MCS7840 USB to Fast Ethernet device. Supports Sitecom LN030. ```ini device uhso ``` Option N.V. HSDPA device. ```ini device rsu ``` Realtek RTL8188SU/RTL8191SU/RTL8192SU wireless driver. ```ini device rum ``` Ralink Technology RT2501USB/RT2601USB wireless driver. ```ini device run ``` Ralink Technology RT2700U/RT2800U/RT3000U wireless driver. ```ini device uath ``` Atheros AR5523 wireless driver. ```ini device upgt ``` Conexant/Intersil PrismGT wireless driver. ```ini device ural ``` Ralink Technology RT2500USB wireless driver. ```ini device urndis ``` RNDIS USB Ethernet driver. ```ini device urtw ``` Realtek RTL8187B/L wireless NIC driver. ```ini device zyd ``` ZyDas ZD1211/ZD1211B wireless driver. ```ini device usie ``` Sierra USB wireless device driver. ```ini options USB_DEBUG options U3G_DEBUG ``` USB subsystem debugging options. ```ini options UKBD_DFLT_KEYMAP # Specify built-in keyboard layout makeoptions UKBD_DFLT_KEYMAP=jp.106 # Set built-in keyboard layout to Japanese 106-key ``` Options for the ukbd driver. ```ini options UPLCOM_INTR_INTERVAL=100 # Interrupt pipe interval (milliseconds) ``` Options for the uplcom driver. ```ini options UVSCOM_DEFAULT_OPKTSIZE=8 # Default output packet size options UVSCOM_INTR_INTERVAL=100 # Interrupt pipe interval (milliseconds) ``` Options for the uvscom driver. ### FireWire (Bus) > **Note** > > FireWire (IEEE 1394) drivers have been marked deprecated in FreeBSD 15.0 and are planned for removal in FreeBSD 16. FireWire hardware has largely exited the market, and new systems do not need to enable this option. ```ini device firewire ``` FireWire bus code. ```ini device sbp ``` FireWire-based SCSI (depends on `scbus` and `da`). ```ini device sbp_targ ``` SBP-2 target mode (depends on `scbus` and `targ`). ```ini device fwe ``` FireWire-based Ethernet (non-standard implementation). ```ini device fwip ``` FireWire-based IP protocol (RFC2734 and RFC3146). ### dcons Dumb Terminal Support (Simple Console Device) ```ini device dcons ``` Dumb terminal driver. ```ini device dcons_crom ``` Dumb terminal FireWire attachment. ```ini options DCONS_BUF_SIZE=16384 ``` Dumb terminal buffer size. ```ini options DCONS_POLL_HZ=100 ``` Dumb terminal polling rate. ```ini options DCONS_FORCE_CONSOLE=0 ``` Force the dumb terminal as the primary console. ```ini options DCONS_FORCE_GDB=1 ``` Force the dumb terminal as the GDB device. ## Cryptographic Subsystem This subsystem is based on the cryptographic framework ported from OpenBSD. It must be included when configuring IPSEC or when hardware cryptographic devices are present, and can accelerate user applications linked with OpenSSL. The relevant drivers are ported from OpenBSD, and include some simple feature enhancements that have been fed back to OpenBSD. ```ini device crypto ``` Core cryptographic subsystem support. ```ini device cryptodev ``` **/dev/crypto**: interface for accessing hardware cryptographic devices. The `cryptodev` device should only be installed when testing or when explicitly known to be needed. In most cases, this device is not required and may cause system performance degradation. ```ini device rndtest ``` FIPS 140-2 entropy testing tool. ```ini device ccr ``` Chelsio T6 cryptographic accelerator driver. ```ini device safe ``` SafeNet SafeXcel 1141/1741 cryptographic accelerator. ```ini options SAFE_DEBUG ``` Enable debug support: `hw.safe.debug`. ```ini options SAFE_RNDTEST ``` Enable [rndtest(4)](https://man.freebsd.org/cgi/man.cgi?query=rndtest\&apropos=0\&sektion=0) (FIPS 140-2 random number generator test monitor) support. ## Embedded Systems ```ini options INIT_PATH=/sbin/init:/rescue/init ``` In embedded systems, it may be necessary to run programs other than init. ### Debugging Options ```ini options BUS_DEBUG ``` Enable newbus debugging. ```ini options DEBUG_VFS_LOCKS ``` Enable VFS lock debugging. ```ini options SOCKBUF_DEBUG ``` Enable sockbuf last record and mbuf tail checking. ```ini options IFMEDIA_DEBUG ``` Enable debugging functionality in `net/if_media.c`. ### SYSINIT Verbose Output ```ini options VERBOSE_SYSINIT ``` Makes the SYSINIT process executed by `mi_startup()` output more verbose information. This is useful when porting to new architectures. If the DDB debugger is also enabled, function names will be displayed instead of addresses. If the value is defined as `0`, the verbose output code will be compiled into the kernel but disabled by default, and can be enabled via the tunable `debug.verbose_sysinit=1`. ## SYSV IPC Kernel Parameters ```ini options SEMMNI=11 ``` Maximum number of System V semaphores that can be used simultaneously by the system. ```ini options SEMMNS=61 ``` Total number of semaphores system-wide. ```ini options SEMMNU=31 ``` Total number of undo structures in the system. ```ini options SEMMSL=61 ``` Maximum number of System V semaphores that can be used simultaneously by a single process. ```ini options SEMOPM=101 ``` Maximum number of operations that can be simultaneously pending on a single System V semaphore. ```ini options SEMUME=11 ``` Maximum number of undo operations that can be simultaneously pending on a single System V semaphore. ```ini options SHMALL=1025 ``` Maximum number of shared memory pages system-wide. ```ini options SHMMAX=(SHMMAXPGS*PAGE_SIZE+1) options SHMMAXPGS=1025 ``` Maximum size of a single System V shared memory region (in bytes). ```ini options SHMMIN=2 ``` Minimum size of a single System V shared memory region (in bytes). ```ini options SHMMNI=33 ``` Maximum number of shared memory regions that can be used simultaneously by the system. ```ini options SHMSEG=9 ``` Maximum number of System V shared memory regions that can be simultaneously attached by a single process. ```ini options PANIC_REBOOT_WAIT_TIME=16 ``` Sets the wait time (in seconds) before the system automatically reboots after a kernel panic. If set to (`-1`), the system will wait indefinitely until any key is pressed on the console. ```ini options DIRECTIO ``` When a file has the `O_DIRECT` flag set, attempts to bypass the buffer cache and read data directly into a user-space buffer. The offset and length of read operations must be multiples of the physical media sector size. ```ini options NSWBUF_MIN=120 ``` Specifies the lower limit for the number of swap I/O buffers. These buffers are used (among other cases) to bypass the buffer cache when the kernel option `DIRECTIO` is enabled and a file has the `O_DIRECT` flag set. ```ini options CAM_DEBUG_DELAY options DEBUG ``` Undocumented lint check option. > **Note** > > No offense is intended by documenting these options. ```ini options LOCKF_DEBUG ``` Kernel file lock debugging. ## System V Compatible Message Queues ```ini options MSGMNB=2049 ``` Maximum number of characters in a queue. > **Note** > > The values given here are for testing kernel builds only. The defaults in the source code provide nearly identical values. `MSGSSZ` must be a power of 2 between `8` and `1024`. ```ini options MSGMNI=41 ``` Maximum number of message queue identifiers. ```ini options MSGSEG=2049 ``` Maximum number of message segments. ```ini options MSGSSZ=16 ``` Message segment size. ```ini options MSGTQL=41 ``` Maximum number of messages in the system. ```ini options NBUF=512 ``` Number of buffer headers. ```ini options SC_DEBUG_LEVEL=5 ``` syscons debug level. ```ini options SC_RENDER_DEBUG ``` syscons render debugging. ```ini options VFS_BIO_DEBUG ``` VFS buffer I/O debugging. ```ini options KSTACK_MAX_PAGES=32 ``` Maximum number of pages allocatable for the kernel stack. ```ini options KSTACK_USAGE_PROF ``` Tracks the maximum stack space used by threads in the kernel. ## Adaptec Array Controller Driver Options ```ini options AAC_DEBUG ``` Debug level: | Level | Description | | ----- | -------------------------------------------------------------------------------------- | | `0` | Silent mode, only displays warning messages | | `1` | Verbose mode, displays major function points and completed operations | | `2` | Extremely verbose mode, displays detailed information such as trace items within loops | ```ini options RACCT ``` Resource accounting. ```ini options RCTL ``` Resource limits. ```ini options MAXFILES=999 ``` Undocumented lint check option. ## Random Number Generator ```ini options RANDOM_FENESTRASX ``` Optional algorithm. ```ini #options RANDOM_LOADABLE ``` Load CSPRNG algorithm as a module. ```ini options RANDOM_ENABLE_UMA # slab allocator ``` Selecting this collects entropy from the Slab allocator at a high frequency (which may be resource-intensive). The value of this feature is questionable in extremely high-frequency scenarios. ```ini options RANDOM_ENABLE_ETHER # Ethernet inbound ``` Selecting this collects entropy from the `m_next` pointer in mbufs at a high frequency (which may be resource-intensive). > **Note** > > Unless receiving jumbo frames exceeding 4 K or achieving sustained data bursts through LRO technology, the `m_next` pointer is typically NULL. Therefore, under normal circumstances, this operation is effectively injecting zero values into the entropy pool. Even if the pointer is non-null, it merely points to a 256-byte-aligned mbuf (whose quantity ranges from thousands to tens of thousands). Thus, even in the best case scenario, this is a poor entropy source. Without actual runtime analysis of entropy collection, users may be misled into believing that far more entropy has been collected than actually achieved, which introduces another class of security risk. In high packet rate scenarios, the cost of Ethernet entropy collection is extremely high, potentially causing up to 50% packet receive loss. This option is provided solely for backward compatibility and is not recommended for use in any environment under any circumstances. ```ini options RANDOM_ENABLE_KBD ``` Collect entropy from the keyboard. ```ini options RANDOM_ENABLE_MOUSE ``` Collect entropy from the mouse. ```ini options RANDOM_ENABLE_TPM # implicitly depends on TPM_HARVEST ``` Collect entropy from the TPM. ```ini options IMGACT_BINMISC ``` Module for enabling application execution through emulators such as QEMU. ## zlib Input/Output Stream Support ```ini options GZIO ``` This option is used to support generating compressed core dump files. ## zstd ```ini options ZSTDIO ``` This option is used to support Zstd-compressed core dump files, GEOM\_UZIP images, and is a required component for the ZFS filesystem when statically linked. ## BHND(4) Driver ```ini options BHND_LOGLEVEL ``` Logging threshold level. ## evdev Interface ```ini device evdev ``` Input event device support. ```ini options EVDEV_SUPPORT ``` evdev support in legacy drivers. ```ini options EVDEV_DEBUG ``` Enable event debug messages. ```ini device uinput ``` Install the character device **/dev/uinput**. ```ini options UINPUT_DEBUG ``` Enable uinput debug messages. ## Encrypted Kernel Crash Dumps ```ini options EKCD ``` Encrypted kernel crash dump functionality. ## Serial Peripheral Interface (SPI) ```ini device spibus ``` SPI bus support. ```ini device at45d device cqspi ``` DataFlash driver. ```ini device mx25l device n25q ``` SPI flash driver. ```ini device spigen ``` User-space generic access support for SPI devices. ```ini options SPIGEN_LEGACY_CDEVNAME ``` Legacy device name for spigen: enables the legacy alias **/dev/spigenN** for **/dev/spigenX.Y** devices. ## Compression Support ```ini device zlib ``` gzip/zlib compression/decompression library. ```ini device xz ``` xz\_embedded LZMA decompression library. ## Kernel stats(3) Support ```ini options STATS ``` Kernel-level stats(3) support. ## File System Monitoring ```ini device filemon ``` File monitoring for make(1) meta mode. ## Intel QuickAssist (QAT) Driver ```ini options QAT_DISABLE_SAFE_DC_MODE ``` Intel QuickAssist (QAT), Intel data protection and compression acceleration technology. 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