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[ikiwiki.git] / docs / handbook / handbook-kernelconfig-config.mdwn

## The Configuration File \r
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`.\r
\r
The following is an example `GENERIC` kernel configuration file with various additional comments where needed for clarity. This example should match your copy in `/usr/src/sys/config/GENERIC` fairly closely. For details of all the possible kernel options, see `/usr/src/sys/config/LINT`.\r
\r
    \r
    #\r
    #\r
    # GENERIC -- Generic kernel configuration file for DragonFly/i386\r
    #\r
    # Check the LINT configuration file in sys/config, for an\r
    # exhaustive list of options.\r
    #\r
    # $DragonFly: src/sys/config/GENERIC,v 1.56 2007/12/26 14:02:36 sephe Exp $\r
\r
The following are the mandatory keywords required in ***every*** kernel you build:\r
\r
    \r
    machine         i386\r
\r
This is the machine architecture. It must be `i386` at the moment.  Support for `amd64` will be added in the future.\r
\r
    \r
    cpu          I386_CPU\r
    cpu          I486_CPU\r
    cpu          I586_CPU\r
    cpu          I686_CPU\r
\r
The above option specifies the type of CPU you have in your system. You may have multiple instances of the CPU line (i.e., you are not sure whether you should use `I586_CPU` or `I686_CPU`), however, for a custom kernel, it is best to specify only the CPU you have. If you are unsure of your CPU type, you can check the `/var/run/dmesg.boot` file to view your boot up messages.\r
\r
    \r
    ident          GENERIC\r
\r
This is the identification of the kernel. You should change this to whatever you named your kernel, i.e. `MYKERNEL` if you have followed the instructions of the previous examples. The value you put in the `ident` string will print when you boot up the kernel, so it is useful to give the new kernel a different name if you want to keep it separate from your usual kernel (i.e. you want to build an experimental kernel).\r
\r
    \r
    maxusers          0\r
\r
The `maxusers` option 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.\r
\r
(Recommended) The system will auto-tune this setting for you if you explicitly set it to `0`[(1)](#FTN.AEN7414). If you want to manage it yourself 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 manual page will start up nine processes to filter, decompress, and view it. Setting `maxusers` to 64 will allow you to have up to 1044 simultaneous processes, which should be enough for nearly all uses. 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, you can always increase the number and rebuild.\r
\r
 **Note:** `maxusers` 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 and X terminal windows*** is [kernelconfig-config.html#KERNELCONFIG-PTYS `pseudo-device pty 16`].\r
\r
    \r
    # Floating point support - do not disable.\r
    device          npx0     at nexus? port IO_NPX irq 13\r
\r
`npx0` is the interface to the floating point math unit in DragonFly, which is either the hardware co-processor or the software math emulator. This is ***not*** optional.\r
\r
    \r
    # Pseudo devices - the number indicates how many units to allocate.\r
    pseudo-device   loop          # Network loopback\r
\r
This 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 device. This is ***mandatory***.\r
\r
Everything that follows is more or less optional. See the notes underneath or next to each option for more information.\r
\r
    \r
    #makeoptions     DEBUG=-g          #Build kernel with gdb(1) debug symbols\r
\r
The normal build process of the DragonFly does not include debugging information when building the kernel and strips most symbols after the resulting kernel is linked, to save some space at the install location. If you are going to do tests of kernels in the DEVELOPMENT branch or develop changes of your own for the DragonFly kernel, you might want to uncomment this line. It will enable the use of the `-g` option which enables debugging information when passed to [gcc(1)](http://leaf.dragonflybsd.org/cgi/web-man?command#gcc&section1).\r
\r
    \r
    options          MATH_EMULATE      #Support for x87 emulation\r
\r
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 486DX, or a 386 or 486SX (with a separate 387 or 487 chip), or higher (Pentium®, Pentium II, etc.), you can comment this line out.\r
\r
 **Note:** The normal math co-processor emulation routines that come with DragonFly are ***not*** very accurate. If you do not have a math co-processor, and you need the best accuracy, it is recommended that you change this option to `GPL_MATH_EMULATE` to use the GNU math support, which is not included by default for licensing reasons.\r
\r
    \r
    options          INET          #InterNETworking\r
\r
Networking support. Leave this 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.\r
\r
    \r
    options          INET6          #IPv6 communications protocols\r
\r
This enables the IPv6 communication protocols.\r
\r
    \r
    options          FFS          #Berkeley Fast Filesystem\r
    options          FFS_ROOT     #FFS usable as root device [keep this!]\r
\r
This is the basic hard drive Filesystem. Leave it in if you boot from the hard disk.\r
\r
    \r
    options          UFS_DIRHASH  #Improve performance on big directories\r
\r
This option includes functionality to speed up disk operations on large directories, at the expense of using additional memory. You would normally keep this for a large server, or interactive workstation, and remove it if you are using DragonFly on a smaller system where memory is at a premium and disk access speed is less important, such as a firewall.\r
\r
    \r
    options          SOFTUPDATES  #Enable FFS Soft Updates support\r
\r
This option enables Soft Updates in the kernel, this will help speed up write access on the disks. Even when this functionality is provided by the kernel, it must be turned on for specific disks. Review the output from [mount(8)](http://leaf.dragonflybsd.org/cgi/web-man?command#mount&section8) to see if Soft Updates is enabled for your system disks. If you do not see the `soft-updates` option then you will need to activate it using the [tunefs(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=tunefs&section=8) (for existing filesystems) or [newfs(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=newfs&section=8) (for new filesystems) commands.\r
\r
    \r
    options          MFS          #Memory Filesystem\r
    options          MD_ROOT      #MD is a potential root device\r
\r
This is the memory-mapped filesystem. 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`:\r
\r
    \r
    /dev/ad1s2b     /tmp mfs rw 0 0\r
\r
Now you simply need to either reboot, or run the command `mount /tmp`.\r
\r
    \r
    options          NFS          #Network Filesystem\r
    options          NFS_ROOT     #NFS usable as root device, NFS required\r
\r
The network Filesystem. Unless you plan to mount partitions from a UNIX® file server over TCP/IP, you can comment these out.\r
\r
    \r
    options          MSDOSFS      #MSDOS Filesystem\r
\r
The 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 pkgsrc®) allows you to access DOS floppies without having to mount and unmount them (and does not require `MSDOSFS` at all).\r
\r
    \r
    options          CD9660       #ISO 9660 Filesystem\r
    options          CD9660_ROOT  #CD-ROM usable as root, CD9660 required\r
\r
The ISO 9660 Filesystem for CDROMs. Comment it out if you do not have a CDROM drive or only mount data CDs occasionally (since it will be dynamically loaded the first time you mount a data CD). Audio CDs do not need this Filesystem.\r
\r
    \r
    options          PROCFS       #Process filesystem\r
\r
The process filesystem. This is a ***pretend*** filesystem mounted on `/proc` which allows programs like [ps(1)](http://leaf.dragonflybsd.org/cgi/web-man?command#ps&section1) to give you more information on what processes are running. ***\r
\r
    \r
\r
Compatibility with 4.3BSD. Leave this in; some programs will act strangely if you comment this out.\r
\r
    \r
    options          SCSI_DELAY=5000    #Delay (in ms) before probing SCSI\r
\r
This causes the kernel to pause for 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 five seconds (5000 ms), to speed up booting. Of course, if you do this, and DragonFly has trouble recognizing your SCSI devices, you will have to raise it back up.\r
\r
    \r
    options          UCONSOLE            #Allow users to grab the console\r
\r
Allow users to grab the console, which is useful for X users. For example, you can create a console ***xterm*** by typing `xterm -C`, which will display any [write(1)](http://leaf.dragonflybsd.org/cgi/web-man?command#write&section1), [talk(1)](http://leaf.dragonflybsd.org/cgi/web-man?command=talk&section=1), and any other messages you receive, as well as any console messages sent by the kernel.\r
\r
    \r
    options          USERCONFIG          #boot -c editor\r
\r
This option allows you to boot the configuration editor from the boot menu.\r
\r
    \r
    options          VISUAL_USERCONFIG   #visual boot -c editor\r
\r
This option allows you to boot the visual configuration editor from the boot menu.\r
\r
    \r
    options          KTRACE              #ktrace(1) support\r
\r
This enables kernel process tracing, which is useful in debugging.\r
\r
    \r
    options          SYSVSHM             #SYSV-style shared memory\r
\r
This option provides for System V shared memory. The most common use of this is the XSHM extension in X, which many graphics-intensive programs will automatically take advantage of for extra speed. If you use X, you will definitely want to include this.\r
\r
    \r
    options          SYSVSEM             #SYSV-style semaphores\r
\r
Support for System V semaphores. Less commonly used but only adds a few hundred bytes to the kernel.\r
\r
    \r
    options          SYSVMSG             #SYSV-style message queues\r
\r
Support for System V messages. Again, only adds a few hundred bytes to the kernel.\r
\r
 **Note:** The [ipcs(1)](http://leaf.dragonflybsd.org/cgi/web-man?command#ipcs&section1) command will list any processes using each of these System V facilities.\r
\r
    \r
    options         P1003_1B                #Posix P1003_1B real-time extensions\r
    options         _KPOSIX_PRIORITY_SCHEDULING\r
\r
Real-time extensions added in the 1993 POSIX®. Certain applications in the ports collection use these (such as  **StarOffice™** ).\r
\r
    \r
    options         ICMP_BANDLIM            #Rate limit bad replies\r
\r
This option enables ICMP error response bandwidth limiting. You typically want this option as it will help protect the machine from denial of service packet attacks.\r
\r
    \r
    # To make an SMP kernel, the next two are needed\r
    #options        SMP                     # Symmetric MultiProcessor Kernel\r
    #options        APIC_IO                 # Symmetric (APIC) I/O\r
\r
The above are both required for SMP support.\r
\r
    \r
    device          isa\r
\r
All PCs supported by DragonFly have one of these. Do not remove, even if you have no ISA slots. If you have an IBM PS/2 (Micro Channel Architecture), DragonFly provides some limited support at this time. For more information about the MCA support, see `/usr/src/sys/config/LINT`.\r
\r
    \r
    device          eisa\r
\r
Include this if you have an EISA motherboard. This enables auto-detection and configuration support for all devices on the EISA bus.\r
\r
    \r
    device          pci\r
\r
Include this if you have a PCI motherboard. This enables auto-detection of PCI cards and gatewaying from the PCI to ISA bus.\r
\r
    \r
    device          agp\r
\r
Include this if you have an AGP card in the system. This will enable support for AGP, and AGP GART for boards which have these features.\r
\r
    \r
    # Floppy drives\r
    device          fdc0        at isa? port IO_FD1 irq 6 drq 2\r
    device          fd0         at fdc0 drive 0\r
    device          fd1         at fdc0 drive 1\r
\r
This is the floppy drive controller. `fd0` is the `A:` floppy drive, and `fd1` is the `B:` drive.\r
\r
    \r
    device          ata\r
\r
This driver supports all ATA and ATAPI devices. You only need one `device ata` line for the kernel to detect all PCI ATA/ATAPI devices on modern machines.\r
\r
    \r
    device          atadisk                 # ATA disk drives\r
\r
This is needed along with `device ata` for ATA disk drives.\r
\r
    \r
    device          atapicd                 # ATAPI CDROM drives\r
\r
This is needed along with `device ata` for ATAPI CDROM drives.\r
\r
    \r
    device          atapifd                 # ATAPI floppy drives\r
\r
This is needed along with `device ata` for ATAPI floppy drives.\r
\r
    \r
    device          atapist                 # ATAPI tape drives\r
\r
This is needed along with `device ata` for ATAPI tape drives.\r
\r
    \r
    options         ATA_STATIC_ID           #Static device numbering\r
\r
This makes the controller number static (like the old driver) or else the device numbers are dynamically allocated.\r
\r
    \r
    # ATA and ATAPI devices\r
    device          ata0        at isa? port IO_WD1 irq 14\r
    device          ata1        at isa? port IO_WD2 irq 15\r
\r
Use the above for older, non-PCI systems.\r
\r
    \r
    # SCSI Controllers\r
    device          ahb        # EISA AHA1742 family\r
    device          ahc        # AHA2940 and onboard AIC7xxx devices\r
    device          amd        # AMD 53C974 (Teckram DC-390(T))\r
    device          dpt        # DPT Smartcache - See LINT for options!\r
    device          isp        # Qlogic family\r
    device          ncr        # NCR/Symbios Logic\r
    device          sym        # NCR/Symbios Logic (newer chipsets)\r
    device          adv0       at isa?\r
    device          adw\r
    device          bt0        at isa?\r
    device          aha0       at isa?\r
    device          aic0       at isa?\r
\r
SCSI controllers. Comment out any you do not have in your system. If you have an IDE only system, you can remove these altogether.\r
\r
    \r
    # SCSI peripherals\r
    device          scbus      # SCSI bus (required)\r
    device          da         # Direct Access (disks)\r
    device          sa         # Sequential Access (tape etc)\r
    device          cd         # CD\r
    device          pass       # Passthrough device (direct SCSI\r
    access)\r
\r
SCSI peripherals. Again, comment out any you do not have, or if you have only IDE hardware, you can remove them completely.\r
\r
 **Note:** The USB [umass(4)](http://leaf.dragonflybsd.org/cgi/web-man?command#umass&section4) driver (and a few other drivers) use the SCSI subsystem even though they are not real SCSI devices. Therefore make sure not to remove SCSI support, if any such drivers are included in the kernel configuration.\r
\r
    \r
    # RAID controllers\r
    device          ida        # Compaq Smart RAID\r
    device          amr        # AMI MegaRAID\r
    device          mlx        # Mylex DAC960 family\r
\r
Supported RAID controllers. If you do not have any of these, you can comment them out or remove them.\r
\r
    \r
    # atkbdc0 controls both the keyboard and the PS/2 mouse\r
    device          atkbdc0    at isa? port IO_KBD\r
\r
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`).\r
\r
    \r
    device          atkbd0     at atkbdc? irq 1\r
\r
The `atkbd` driver, together with `atkbdc` controller, provides access to the AT 84 keyboard or the AT enhanced keyboard which is connected to the AT keyboard controller.\r
\r
    \r
    device          psm0       at atkbdc? irq 12\r
\r
Use this device if your mouse plugs into the PS/2 mouse port.\r
\r
    \r
    device          vga0        at isa?\r
\r
The video card driver.\r
\r
    \r
    # splash screen/screen saver\r
    pseudo-device          splash\r
\r
Splash screen at start up! Screen savers require this too.\r
\r
    \r
    # syscons is the default console driver, resembling an SCO console\r
    device          sc0          at isa?\r
\r
`sc0` is the default console driver, which resembles a SCO console. Since most full-screen programs access the console through a terminal database library like `termcap`, it should not matter 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.\r
\r
    \r
    # Enable this and PCVT_FREEBSD for pcvt vt220 compatible console driver\r
    #device          vt0     at isa?\r
    #options         XSERVER          # support for X server on a vt console\r
    #options         FAT_CURSOR       # start with block cursor\r
    # If you have a ThinkPAD, uncomment this along with the rest of the PCVT lines\r
    #options         PCVT_SCANSET=2   # IBM keyboards are non-std\r
\r
This is a VT220-compatible console driver, backward 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 `termcap` or `terminfo` entries for the `sc0` device are often not available -- `vt100` should be available on virtually any platform.\r
\r
    \r
    # Power management support (see LINT for more options)\r
    device          apm0     at nexus? disable flags 0x20  # Advanced Power Management\r
\r
Advanced Power Management support. Useful for laptops.\r
\r
    \r
    # PCCARD (PCMCIA) support\r
    device          card\r
    device          pcic0    at isa? irq 10 port 0x3e0 iomem 0xd0000\r
    device          pcic1    at isa? irq 11 port 0x3e2 iomem 0xd4000 disable\r
\r
PCMCIA support. You want this if you are using a laptop.\r
\r
    \r
    # Serial (COM) ports\r
    device          sio0     at isa? port IO_COM1 flags 0x10 irq 4\r
    device          sio1     at isa? port IO_COM2 irq 3\r
    device          sio2     at isa? disable port IO_COM3 irq 5\r
    device          sio3     at isa? disable port IO_COM4 irq 9\r
\r
These are the four serial ports referred to as COM1 through COM4 in the MS-DOS/Windows® world.\r
\r
 **Note:** 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, IRQ2 # IRQ 9) in order to access it from DragonFly. If you have a multiport serial card, check the manual page for [sio(4)](http://leaf.dragonflybsd.org/cgi/web-man?commandsio&section=4) for more information on the proper values for these lines. Some video cards (notably those based on S3 chips) use IO addresses in the form of `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.\r
\r
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.\r
\r
    \r
    # Parallel port\r
    device          ppc0    at isa? irq 7\r
\r
This is the ISA-bus parallel port interface.\r
\r
    \r
    device          ppbus      # Parallel port bus (required)\r
\r
Provides support for the parallel port bus.\r
\r
    \r
    device          lpt        # Printer\r
\r
Support for parallel port printers.\r
\r
 **Note:** All three of the above are required to enable parallel printer support.\r
\r
    \r
    device          plip       # TCP/IP over parallel\r
\r
This is the driver for the parallel network interface.\r
\r
    \r
    device          ppi        # Parallel port interface device\r
\r
The general-purpose I/O (***geek port) + IEEE1284 I/O.\r
\r
    \r
    #device         vpo        # Requires scbus and da\r
\r
This is for an Iomega Zip drive. It requires `scbus` and `da` support. Best performance is achieved with ports in EPP 1.9 mode.\r
\r
    \r
    # PCI Ethernet NICs.\r
    device          de         # DEC/Intel DC21x4x (Tulip)\r
    device          fxp        # Intel EtherExpress PRO/100B (82557, 82558)\r
    device          tx         # SMC 9432TX (83c170 EPIC)\r
    device          vx         # 3Com 3c590, 3c595 (Vortex)\r
    device          wx         # Intel Gigabit Ethernet Card (Wiseman)\r
\r
Various PCI network card drivers. Comment out or remove any of these not present in your system.\r
\r
    \r
    # PCI Ethernet NICs that use the common MII bus controller code.\r
    device          miibus     # MII bus support\r
\r
MII bus support is required for some PCI 10/100 Ethernet NICs, namely those which use MII-compliant transceivers or implement transceiver control interfaces that operate like an MII. Adding `device miibus` to the kernel config pulls in support for the generic miibus API and all of the PHY drivers, including a generic one for PHYs that are not specifically handled by an individual driver.\r
\r
    \r
    device          dc         # DEC/Intel 21143 and various workalikes\r
    device          rl         # RealTek 8129/8139\r
    device          sf         # Adaptec AIC-6915 (Starfire)\r
    device          sis        # Silicon Integrated Systems SiS 900/SiS 7016\r
    device          ste        # Sundance ST201 (D-Link DFE-550TX)\r
    device          tl         # Texas Instruments ThunderLAN\r
    device          vr         # VIA Rhine, Rhine II\r
    device          wb         # Winbond W89C840F\r
    device          xl         # 3Com 3c90x (Boomerang, Cyclone)\r
\r
Drivers that use the MII bus controller code.\r
\r
    \r
    # ISA Ethernet NICs.\r
    device          ed0    at isa? port 0x280 irq 10 iomem 0xd8000\r
    device          ex\r
    device          ep\r
    # WaveLAN/IEEE 802.11 wireless NICs. Note: the WaveLAN/IEEE really\r
    # exists only as a PCMCIA device, so there is no ISA attachment needed\r
    # and resources will always be dynamically assigned by the pccard code.\r
    device          wi\r
    # Aironet 4500/4800 802.11 wireless NICs. Note: the declaration below will\r
    # work for PCMCIA and PCI cards, as well as ISA cards set to ISA PnP\r
    # mode (the factory default). If you set the switches on your ISA\r
    # card for a manually chosen I/O address and IRQ, you must specify\r
    # those parameters here.\r
    device          an\r
    # The probe order of these is presently determined by i386/isa/isa_compat.c.\r
    device          ie0    at isa? port 0x300 irq 10 iomem 0xd0000\r
    device          fe0    at isa? port 0x300\r
    device          le0    at isa? port 0x300 irq 5 iomem 0xd0000\r
    device          lnc0   at isa? port 0x280 irq 10 drq 0\r
    device          cs0    at isa? port 0x300\r
    device          sn0    at isa? port 0x300 irq 10\r
    # requires PCCARD (PCMCIA) support to be activated\r
    #device         xe0    at isa?\r
\r
ISA Ethernet drivers. See `/usr/src/sys/config/LINT` for which cards are supported by which driver.\r
\r
    \r
    pseudo-device   ether         # Ethernet support\r
\r
`ether` is only needed if you have an Ethernet card. It includes generic Ethernet protocol code.\r
\r
    \r
    pseudo-device   sl      1     # Kernel SLIP\r
\r
`sl` is for SLIP support. This has been almost entirely supplanted by PPP, which is easier to set up, better suited for modem-to-modem connection, and more powerful. The ***number*** after `sl` specifies how many simultaneous SLIP sessions to support.\r
\r
    \r
    pseudo-device   ppp     1     # Kernel PPP\r
\r
This is for kernel PPP support for dial-up connections. There is also a version of PPP implemented as a userland application that uses `tun` and offers more flexibility and features such as demand dialing. The ***number*** after `ppp` specifies how many simultaneous PPP connections to support. .\r
\r
    \r
    device   tun           # Packet tunnel.\r
\r
This is used by the userland PPP software. A ***number*** after `tun` specifies the number of simultaneous PPP sessions to support. See the [userppp.html PPP] section of this book for more information.\r
\r
    \r
    pseudo-device   pty           # Pseudo-ttys (telnet etc)\r
\r
This 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*** after `pty` indicates the number of `pty`s to create. If you need more than the default of 16 simultaneous ***xterm*** windows and/or remote logins, be sure to increase this number accordingly, up to a maximum of 256. ***\r
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    \r
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Memory disk pseudo-devices.\r
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    \r
    pseudo-device   gif     # IPv6 and IPv4 tunneling\r
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This implements IPv6 over IPv4 tunneling, IPv4 over IPv6 tunneling, IPv4 over IPv4 tunneling, and IPv6 over IPv6 tunneling.\r
\r
    \r
    pseudo-device   faith   # IPv6-to-IPv4 relaying (translation)\r
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This pseudo-device captures packets that are sent to it and diverts them to the IPv4/IPv6 translation daemon.\r
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    \r
    # The `bpf' device enables the Berkeley Packet Filter.\r
    # Be aware of the administrative consequences of enabling this!\r
    pseudo-device   bpf           # Berkeley packet filter\r
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This is the 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)](http://leaf.dragonflybsd.org/cgi/web-man?command#tcpdump&section1) program.\r
\r
 **Note:** The [bpf(4)](http://leaf.dragonflybsd.org/cgi/web-man?command#bpf&section4) device is also used by [dhclient(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=dhclient&section=8) to obtain the IP address of the default router (gateway) and so on. If you use DHCP, leave this uncommented.\r
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    \r
    # USB support\r
    #device         uhci          # UHCI PCI->USB interface\r
    #device         ohci          # OHCI PCI->USB interface\r
    #device         usb           # USB Bus (required)\r
    #device         ugen          # Generic\r
    #device         uhid          # ***Human Interface Devices***\r
    #device         ukbd          # Keyboard\r
    #device         ulpt          # Printer\r
    #device         umass         # Disks/Mass storage - Requires scbus and da\r
    #device         ums           # Mouse\r
    # USB Ethernet, requires mii\r
    #device         aue           # ADMtek USB ethernet\r
    #device         cue           # CATC USB ethernet\r
    #device         kue           # Kawasaki LSI USB ethernet\r
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Support for various USB devices.\r
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For more information and additional devices supported by DragonFly, see `/usr/src/sys/i386/conf/LINT`.\r
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#### Notes \r
[[!table  data="""
|<tablewidth="100%"> [(1)](kernelconfig-config.html#AEN7414) | The auto-tuning algorithm sets `maxuser` equal to the amount of memory in the system, with a minimum of 32, and a maximum of 384. |\r
"""]]\r
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