The general format of a configuration file is quite simple. Each line contains a keyword and one or more arguments. For simplicity, most lines only contain one argument. Anything following a # is considered a comment and ignored. The following sections describe each keyword, generally in the order they are listed in GENERIC, although some related keywords have been grouped together in a single section (such as Networking) even though they are actually scattered throughout the GENERIC file. An exhaustive list of options and more detailed explanations of the device lines is present in the LINT configuration file, located in the same directory as GENERIC. If you are in doubt as to the purpose or necessity of a line, check first in LINT.
The kernel is currently being moved to a better organization of the option handling. Traditionally, each option in the config file was simply converted into a -D switch for the CFLAGS line of the kernel Makefile. Naturally, this caused a creeping optionism, with nobody really knowing which option has been referenced in what files.
In the new scheme, every #ifdef that is intended to be dependent upon an option gets this option out of an opt_foo.h declaration file created in the compile directory by config. The list of valid options for config lives in two files: options that do not depend on the architecture are listed in /sys/conf/options, architecture-dependent ones in /sys/arch/conf/options.arch, with arch being for example i386.
Quoting numbers: In all versions of FreeBSD up to and including 3-stable, config(8) required that any strings in the configuration file that contained numbers used as text had to be enclosed in double quotes.
Where numbers are used as numbers, as in maxusers 64, the quotation marks are not required.
This requirement was removed in FreeBSD-current (the 4.0 release candidate).
The examples here include the quote marks ("). If you are building a kernel on a -current system you should omit them.
These keywords are required in every kernel you build.
The first keyword is machine, which, since FreeBSD only runs on Intel 386 (and compatible) chips and DEC Alpha processors, will be either i386 or alpha.
The next keyword is cpu, which includes support for each CPU supported by FreeBSD. The possible values of cpu_type for i386 systems include:
The values available for cpu_type for Alpha systems include:
Multiple instances of the cpu line may be present with different values of cpu_type as are present in the GENERIC kernel. For a custom kernel, it is best to specify only the cpu you have. If, for example, you have an Intel Pentium, use I586_CPU for cpu_type.
Next, we have ident, which is the identification of the kernel. You should change this from GENERIC to whatever you named your kernel, in this example, MYKERNEL. The value you put in ident will print when you boot up the kernel, so it is useful to give a kernel a different name if you want to keep it separate from your usual kernel (if you want to build an experimental kernel, for example). Note that, as with machine and cpu, enclose your kernel's name in quotation marks if it contains any numbers.
Since this name is passed to the C compiler as a -D switch, do not use names like DEBUG, or something that could be confused with another machine or CPU name, like vax.
This file sets the size of a number of important system tables. This number is supposed to be roughly equal to the number of simultaneous users you expect to have on your machine. However, under normal circumstances, you will want to set maxusers to at least 4, especially if you are using the X Window System or compiling software. The reason is that the most important table set by maxusers is the maximum number of processes, which is set to 20 + 16 * maxusers, so if you set maxusers to 1, then you can only have 36 simultaneous processes, including the 18 or so that the system starts up at boot time, and the 15 or so you will probably create when you start the X Window System. Even a simple task like reading a man page will start up nine processes to filter, decompress, and view it. Setting maxusers to 4 will allow you to have up to 84 simultaneous processes, which should be enough for anyone. If, however, you see the dreaded proc table full error when trying to start another program, or are running a server with a large number of simultaneous users (like Walnut Creek CDROM's FTP site), you can always increase this number and rebuild.
Note: maxuser does not limit the number of users which can log into your machine. It simply sets various table sizes to reasonable values considering the maximum number of users you will likely have on your system and how many processes each of them will be running. One keyword which does limit the number of simultaneous remote logins is pseudo-device pty 16.
This line specifies the location and name of the kernel. Traditionally the kernel is called vmunix but in FreeBSD, it is aptly named kernel. You should always use kernel for kernel_name because changing it will render numerous system utilities inoperative. The second part of the line specifies the disk and partition where the root filesystem and kernel can be found. Typically this will be wd0 for systems with non-SCSI drives, or da0 for systems with SCSI drives.
These lines provide kernel support for various filesystems and other options.
This line allows the kernel to simulate a math co-processor if your computer does not have one (386 or 486SX). If you have a Pentium, a 486DX, or a 386 or 486SX with a separate 387 or 487 chip, you can comment this line out.
Note: The normal math co-processor emulation routines that come with FreeBSD are not very accurate. If you do not have a math co-processor, and you need the best accuracy, I recommend that you change this option to GPL_MATH_EMULATE to use the superior GNU math support, which is not included by default for licensing reasons.
Compatibility with 4.3BSD. Leave this in; some programs will act strangely if you comment this out.
ISA devices and EISA devices operating in an ISA compatibility mode can only perform DMA (Direct Memory Access) to memory below 16 megabytes. This option enables such devices to work in systems with more than 16 megabytes of memory.
Allow users to grab the console, useful for X Windows. For example, you can create a console xterm by typing xterm -C, which will display any write, talk, and other messages you receive, as well as any console messages sent by the kernel.
This option provides for System V shared memory. The most common use of this is the XSHM extension in X Windows, which many graphics-intensive programs (such as the movie player XAnim, and Linux DOOM) will automatically take advantage of for extra speed. If you use the X Window System, you will definitely want to include this.
Support for System V semaphores. Less commonly used but only adds a few hundred bytes to the kernel.
Support for System V messages. Again, only adds a few hundred bytes to the kernel.
Note: The ipcs(1) command will tell will list any processes using each of these System V facilities.
These options add support for various filesystems. You must include at least one of these to support the device you boot from; typically this will be FFS if you boot from a hard drive, or NFS if you are booting a diskless workstation from Ethernet. You can include other commonly-used filesystems in the kernel, but feel free to comment out support for filesystems you use less often (perhaps the MS-DOS filesystem?), since they will be dynamically loaded from the Kernel Module directory /modules the first time you mount a partition of that type.
The basic hard drive filesystem; leave it in if you boot from the hard disk.
Network Filesystem. Unless you plan to mount partitions from a Unix file server over Ethernet, you can comment this out.
MS-DOS Filesystem. Unless you plan to mount a DOS formatted hard drive partition at boot time, you can safely comment this out. It will be automatically loaded the first time you mount a DOS partition, as described above. Also, the excellent mtools software (in the ports collection) allows you to access DOS floppies without having to mount and unmount them (and does not require MSDOSFS at all).
ISO 9660 filesystem for CD-ROMs. Comment it out if you do not have a CD-ROM drive or only mount data CD's occasionally (since it will be dynamically loaded the first time you mount a data CD). Audio CD's do not need this filesystem.
Process filesystem. This is a pretend filesystem mounted on /proc which allows programs like ps(1) to give you more information on what processes are running.
Memory-mapped file system. This is basically a RAM disk for fast storage of temporary files, useful if you have a lot of swap space that you want to take advantage of. A perfect place to mount an MFS partition is on the /tmp directory, since many programs store temporary data here. To mount an MFS RAM disk on /tmp, add the following line to /etc/fstab and then reboot or type mount /tmp:
/dev/wd1s2b /tmp mfs rw 0 0
Note: Replace the /dev/wd1s2b with the name of your swap partition, which will be listed in your /etc/fstab as follows:/dev/wd1s2b none swap sw 0 0
Note: Also, the MFS filesystem can not be dynamically loaded, so you must compile it into your kernel if you want to experiment with it.
Linux's native file system. With ext2fs support you are able to read and write to Linux partitions. This is useful if you dual-boot FreeBSD and Linux and want to share data between the two systems.
Enable disk quotas. If you have a public access system, and do not want users to be able to overflow the /home partition, you can establish disk quotas for each user. Refer to the Disk Quotas section for more information.
All PC's supported by FreeBSD have one of these. If you have an IBM PS/2 (Micro Channel Architecture), then you cannot run FreeBSD at this time.
Include this if you have a PCI motherboard. This enables auto-detection of PCI cards and gatewaying from the PCI to the ISA bus.
Floppy drive controller: fd0 is the A: floppy drive, and fd1 is the B: drive. ft0 is a QIC-80 tape drive attached to the floppy controller. Comment out any lines corresponding to devices you do not have.
Note: QIC-80 tape support requires a separate filter program called ft(8), see the manual page for details.
This is the primary IDE controller. wd0 and wd1 are the master and slave hard drive, respectively. wdc1 is a secondary IDE controller where you might have a third or fourth hard drive, or an IDE CD-ROM. Comment out the lines which do not apply (if you have a SCSI hard drive, you will probably want to comment out all six lines, for example).
This device provides IDE CD-ROM support. Be sure to leave wdc0 uncommented, and wdc1 if you have more than one IDE controller and your CD-ROM is on the second one card. To use this, you must also include the line options ATAPI.
npx0 is the interface to the floating point math unit in FreeBSD, either the hardware co-processor or the software math emulator. It is not optional.
Wangtek and Archive QIC-02/QIC-36 tape drive support
The following drivers are for the so-called proprietary CD-ROM drives. These drives have their own controller card or might plug into a sound card such as the SoundBlaster 16. They are not IDE or SCSI. Most older single-speed and double-speed CD-ROMs use these interfaces, while newer quad-speeds are likely to be IDE or SCSI.
Mitsumi CD-ROM (LU002, LU005, FX001D).
Sony CD-ROM (CDU31, CDU33A).
Matsushita/Panasonic CD-ROM (sold by Creative Labs for SoundBlaster).
This section describes the various SCSI controllers and devices supported by FreeBSD.
The next ten or so lines include support for different kinds of SCSI controllers. Comment out all except for the one(s) you have:
Most Buslogic controllers
UltraStor 14F and 34F
Adaptec 152x and sound cards using Adaptec AIC-6360 (slow!)
ProAudioSpectrum cards using NCR 5380 or Trantor T130
Seagate ST01/02 8 bit controller (slow!)
Western Digital WD7000 controller
NCR 53C810, 53C815, 53C825, 53C860, 53C875 PCI SCSI controller
Note: This also supports the Diamond FirePort controller.
This causes the kernel to pause 15 seconds before probing each SCSI device in your system. If you only have IDE hard drives, you can ignore this, otherwise you will probably want to lower this number, perhaps to 5 seconds, to speed up booting. Of course if you do this, and FreeBSD has trouble recognizing your SCSI devices, you will have to raise it back up.
If you have any SCSI controllers, this line provides generic SCSI support. If you do not have SCSI, you can comment this, and the following three lines, out.
Support for SCSI hard drives.
Support for SCSI tape drives.
Support for SCSI CD-ROM drives.
Note that the number 0 in the above entries is slightly misleading: all these devices are automatically configured as they are found, regardless of how many of them are hooked up to the SCSI bus(es), and which target IDs they have.
If you want to ``wire down'' specific target IDs to particular devices, refer to the appropriate section of the LINT kernel config file.
You must choose one of these two console types, and, if you plan to use the X Window System with the vt220 console, enable the XSERVER option and optionally, a bus mouse or PS/2 mouse device.
sc0 is the default console driver, which resembles an SCO console. Since most full-screen programs access the console through a terminal database library like termcap, it should not matter much whether you use this or vt0, the VT220 compatible console driver. When you log in, set your TERM variable to ``scoansi'' if full-screen programs have trouble running under this console.
The keyboard controller atkbdc provides I/O services for the AT keyboard and PS/2 style pointing devices. This controller is required by the keyboard driver atkbd and the PS/2 pointing device driver psm.
The keyboard driver atkbd and the pointing device driver psm may ask the atkbdc driver to reset the devices during the boot process. It sometimes takes a long time before these devices respond to the reset command. These options control how long the atkbdc driver should wait before giving up --- the driver will wait X * Y milliseconds at most. If the drivers seem unable to detect devices, you may want to increase these values. The default values are 200 milliseconds for X and 5 for Y.
Sets the debug level to N. The default value is zero, which suppresses all debugging output.
Note: There can only be one atkbdc device configured into the system.
The atkbd driver, together with the atkbdc controller, provides access to the AT 84 keyboard or the AT enhanced keyboard which is connected to the AT keyboard controller.
This is a VT220-compatible console driver, backwards compatible to VT100/102. It works well on some laptops which have hardware incompatibilities with sc0. Also, set your TERM variable to vt100 or vt220 when you log in. This driver might also prove useful when connecting to a large number of different machines over the network, where the termcap or terminfo entries for the sc0 device are often not available --- vt100 should be available on virtually any platform.
Required with the vt0 console driver.
Only applicable with the vt0 console driver. This includes code required to run the XFree86 X Window Server under the vt0 console driver.
Use this device if you have a Logitech or ATI InPort bus mouse card.
Note: If you have a serial mouse, ignore these two lines, and instead, make sure the appropriate serial port is enabled (probably COM1).
Use this device if your mouse plugs into the PS/2 mouse port.
Nearly all systems have these. If you are attaching a printer to one of these ports, the Printing section of the handbook is very useful. If you are using modem, Dialup access provides extensive detail on serial port configuration for use with such devices.
sio0 through sio3 are the four serial ports referred to as COM1 through COM4 in the MS-DOS world. Note that if you have an internal modem on COM4 and a serial port at COM2 you will have to change the IRQ of the modem to 2 (for obscure technical reasons IRQ 2 = IRQ 9) in order to access it from FreeBSD. If you have a multiport serial card, check the manual page for sio(4) for more information on the proper values for these lines. Some video cards (notably those based on S3 chips) use IO addresses of the form 0x*2e8, and since many cheap serial cards do not fully decode the 16-bit IO address space, they clash with these cards, making the COM4 port practically unavailable.
Each serial port is required to have a unique IRQ (unless you are using one of the multiport cards where shared interrupts are supported), so the default IRQs for COM3 and COM4 cannot be used.
lpt0 through lpt2 are the three printer ports you could conceivably have. Most people just have one, though, so feel free to comment out the other two lines if you do not have them.
FreeBSD, as with Unix in general, places a big emphasis on networking. Therefore, even if you do not have an Ethernet card, pay attention to the mandatory options and the dial-up networking support.
Networking support. Leave it in even if you do not plan to be connected to a network. Most programs require at least loopback networking (i.e. making network connections within your PC) so this is essentially mandatory.
The next lines enable support for various Ethernet cards. If you do not have a network card, you can comment out all of these lines. Otherwise, you will want to leave in support for your particular Ethernet card(s):
IBM Etherjet and other Crystal Semi CS89x0-based adapters.
Ethernet adapters based on Digital Equipment DC21040, DC21041 or DC21140 chips
Intel EtherExpress Pro/100B
3Com 3C590 and 3C595 (buggy)
Cronyx/Sigma multiport sync/async (with Cisco or PPP framing)
Western Digital and SMC 80xx and 8216; Novell NE1000 and NE2000; 3Com 3C503; HP PC Lan Plus (HP27247B and HP27252A)
3Com 3C501 (slow!)
3Com 3C509 (buggy)
Fujitsu MB86960A/MB86965A Ethernet
DEC DEFEA EISA FDDI adapter
AT&T StarLAN 10 and EN100; 3Com 3C507; unknown NI5210; Intel EtherExpress 16
Digital Equipment EtherWorks 2 and EtherWorks 3 (DEPCA, DE100, DE101, DE200, DE201, DE202, DE203, DE204, DE205, DE422)
Lance/PCnet cards (Isolan, Novell NE2100, NE32-VL)
3Com Etherlink XL series PCI ethernet controllers (3C905B and related).
IBM/National Semiconductor PCMCIA ethernet controller.
3Com PCMCIA Etherlink III
Note: With certain cards (notably the NE2000) you will have to change the port and/or IRQ since there is no ``standard'' location for these cards.
loop is the generic loopback device for TCP/IP. If you telnet or FTP to localhost (a.k.a. 127.0.0.1) it will come back at you through this pseudo-device. Mandatory.
ether is only needed if you have an Ethernet card and includes generic Ethernet protocol code.
sl is for SLIP (Serial Line Internet Protocol) support. This has been almost entirely supplanted by PPP, which is easier to set up, better suited for modem-to-modem connections, as well as more powerful. The number after sl specifies how many simultaneous SLIP sessions to support. This handbook has more information on setting up a SLIP client or server.
ppp is for kernel-mode PPP (Point-to-Point Protocol) support for dial-up Internet connections. There is also version of PPP implemented as a user application that uses the tun and offers more flexibility and features such as demand dialing. If you still want to use this PPP driver, read the kernel-mode PPP section of the handbook. As with the sl device, number specifies how many simultaneous PPP connections to support.
tun is used by the user-mode PPP software. This program is easy to set up and very fast. It also has special features such as automatic dial-on-demand. The number after tun specifies the number of simultaneous PPP sessions to support. See the user-mode PPP section of the handbook for more information.
Berkeley packet filter. This pseudo-device allows network interfaces to be placed in promiscuous mode, capturing every packet on a broadcast network (e.g. an ethernet). These packets can be captured to disk and/or examined with the tcpdump(1) program. Note that implementation of this capability can seriously compromise your overall network security. The number after bpfilter is the number of interfaces that can be examined simultaneously. Optional, not recommended except for those who are fully aware of the potential pitfalls. Not all network cards support this capability.
This is the first section containing lines that are not in the GENERIC kernel. To include sound card support, you will have to copy the appropriate lines from the LINT kernel (which support for every device) as follows:
Generic sound driver code. Required for all of the following sound cards except pca.
ProAudioSpectrum digital audio and MIDI.
SoundBlaster digital audio.
Note: If your SoundBlaster is on a different IRQ (such as 5), change irq 7 to, for example, irq 5 and remove the conflicts keyword.
SoundBlaster 16 digital 16-bit audio.
Note: If your SB16 is on a different 16-bit DMA channel (such as 6 or 7), change the drq 5 keyword appropriately.
SoundBlaster 16 MIDI interface. If you have a SoundBlaster 16, you must include this line, or the kernel will not compile.
Microsoft Sound System.
AdLib FM-synthesis audio. Include this line for AdLib, SoundBlaster, and ProAudioSpectrum users, if you want to play MIDI songs with a program such as playmidi (in the ports collection).
Roland MPU-401 stand-alone card.
Stand-alone 6850 UART for MIDI.
Digital audio through PC speaker. This is going to be very poor sound quality and quite CPU-intensive, so you have been warned (but it does not require a sound card).
The pcm driver provides support for various ISA sound cards that are compatible with the WSS/MSS specs, or with the Sound Blaster Pro and Sound Blaster 16.
Note: There is some additional documentation in /usr/src/sys/i386/isa/sound/. Also, if you add any of these devices, be sure to create the sound device nodes.
Pseudo-device drivers are parts of the kernel that act like device drivers but do not correspond to any actual hardware in the machine. The network-related pseudo-devices are in that section, while the remainder are here.
gzip allows you to run FreeBSD programs that have been compressed with gzip. The programs in /stand are compressed so it is a good idea to have this option in your kernel.
Note: The gzip feature currently only works with a.out binaries.
log is used for logging of kernel error messages. Mandatory.
pty is a ``pseudo-terminal'' or simulated login port. It is used by incoming telnet and rlogin sessions, xterm, and some other applications such as emacs. The number indicates the number of ptys to create. If you need more than GENERIC default of 16 simultaneous xterm windows and/or remote logins, be sure to increase this number accordingly, up to a maximum of 256.
Snoop device. This pseudo-device allows one terminal session to watch another using the watch(8) command. Note that implementation of this capability has important security and privacy implications. The number after snp is the total number of simultaneous snoop sessions. Optional.
Vnode driver. Allows a file to be treated as a device after being set up with the vnconfig(8) command. This driver can be useful for manipulating floppy disk images and using a file as a swap device (e.g. an MS Windows swap file). Optional.
Concatenated disks. This pseudo-device allows you to concatenate multiple disk partitions into one large ``meta''-disk. The number after ccd is the total number of concatenated disks (not total number of disks that can be concatenated) that can be created. (See ccd(4) and ccdconfig(8) man pages for more details.) Optional.
This section describes some miscellaneous hardware devices supported by FreeBSD. Note that none of these lines are included in the GENERIC kernel, you will have to copy them from this handbook or the LINT kernel (which contains support for every device):
PC joystick device.
Supports IBM BASIC-style noises through the PC speaker. Some fun programs which use this are /usr/sbin/spkrtest, which is a shell script that plays some simple songs, and /usr/games/piano which lets you play songs using the keyboard as a simple piano (this file only exists if you have installed the games package). Also, the excellent text role-playing game NetHack (in the ports collection) can be configured to use this device to play songs when you play musical instruments in the game.
See also the pca0 device.