BOOT_CONFIG(8)          OpenBSD System Manager's Manual         BOOT_CONFIG(8)

NAME
     boot_config - how to change kernel configuration at boot

DESCRIPTION
     BOOT_CONFIG is a kernel option that makes it possible to change the con-
     figuration at boot time.  The same interface is available from userland,
     using the -e argument to config(8).

     The boot time configuration is invoked by the -c option when OpenBSD
     prompts for a kernel to boot:

     >> OpenBSD BOOT 640/31744 k [1.29]
     use ? for file list, or carriage return for defaults
     use hd(1,a)/bsd to boot sd0 when sd0 is also installed
     Boot: [[[wd(0,a)]/bsd][-abcdrs]]: -c
     Booting...
     avail mem = 28188672
     using 430 buffers containing 1761280 bytes of memory
     User Kernel Config
     UKC>

     Changes made can be saved for the next reboot, by using config(8).

COMMANDS
     add dev              Add a device through copying another.

     base 8 | 10 | 16     Change the base of numbers displayed and entered,
                          e.g. I/O addresses in a VAXen are octal.

     change devno | dev   Modify one or more devices.

     disable devno | dev  Disable one or more devices.

     enable devno | dev   Enable one or more devices.

     exit                 Continue boot.

     find devno | dev     Find one or more devices.

     help                 Give a short summary of all commands and their argu-
                          ments.

     list                 Show all known devices, a screen at a time.

     lines [count]        Set the number of rows per page.

     quit                 Continue boot.

     show [attr [val]]    Show all devices for which attribute attr has the
                          value val.

     timezone [minuteswest [dst]]
                          Change the tz timezone structure.  minuteswest is
                          the number of minutes west of GMT and dst is non-ze-
                          ro if Daylight Saving Time is in effect.  Without
                          arguments, displays its current value.

     verbose              Toggle the autoconfig verbose variable.

EXAMPLES
     The Ethernet card is not detected at boot because the kernel configura-
     tion does not match the physical hardware configuration, e.g. wrong IRQ
     in OpenBSD/i386.  The Ethernet card is supposed to use the ne(4) driver.

     UKC> find ne
     24 ne0 at isa0 port 0x240 size 0 iomem 0xd8000 iosiz 0 irq 9 drq -1 drq2 -1 flags 0x0
     25 ne1 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 10 drq -1 drq2 -1 flags 0x0
     26 ne* at isapnp0 port -1 size 0 iomem -1 iosiz 0 irq -1 drq -1 flags 0x0
     27 ne* at pci* dev -1 function -1 flags 0x0
     28 ne* at pcmcia* function -1 irq -1 flags 0x0
     UKC>

     ne1 seems to match the configuration except it uses IRQ 5 instead of IRQ
     10.  So the irq on ne1 should be changed via the change command.  The de-
     vice can be specified by either name or number.

     UKC> change ne1
     25 ne1 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 10 drq -1 drq2 -1 flags 0x0
     change (y/n) ? y
     port [0x300] ?
     size [0] ?
     iomem [-1] ?
     iosiz [0] ?
     irq [10] ? 5
     drq [-1] ?
     drq2 [-1] ?
     flags [0] ?
     25 ne1 changed
     25 ne1 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 5 drq -1 drq2 -1 flags 0x0
     UKC>

     Another case is a mistakenly detected non-existing device instead of an-
     other device at the probed location.  One known case is the Mitsumi CD-
     ROM in OpenBSD/i386.  The simplest thing to solve that problem is to dis-
     able mcd0.

     UKC> find mcd0
      29 mcd0 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 10 drq -1 drq2 -1 flags 0x0
     UKC> disable mcd0
      29 mcd0 disabled
     UKC> find 29
      29 mcd0 at isa0 disable port 0x300 size 0 iomem -1 iosiz 0 irq 10 drq -1 drq2 -1 flags 0x0

     The show command is useful for finding which devices have a certain at-
     tribute.  It can also be used to find those devices with a particular
     value for an attribute.

     UKC> show slot
       2 ahc* at eisa0 slot -1 flags 0x0
      10 uha* at eisa0 slot -1 flags 0x0
      12 ep0 at eisa0 slot -1 flags 0x0
      17 ep* at eisa0 slot -1 flags 0x0
     102 ahb* at eisa0 slot -1 flags 0x0
     103 fea* at eisa0 slot -1 flags 0x0
     UKC> show port 0x300
      25 ne1 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 10 drq -1 drq2 -1 flags 0x0
      72 we1 at isa0 port 0x300 size 0 iomem 0xcc000 iosiz 0 irq 10 drq -1 drq2 -1 flags 0x0
      75 el0 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 9 drq -1 drq2 -1 flags 0x0
      77 ie1 at isa0 port 0x300 size 0 iomem -1 iosiz 0 irq 10 drq -1 drq2 -1 flags 0x0
     UKC>

     It is possible to add new devices, but only devices that were linked into
     the kernel.  If a new device is added, following devices will be renum-
     bered.

     UKC> find ep
      11 ep0 at isa0 port -1 size 0 iomem -1 iosiz 0 irq -1 drq -1 drq2 -1 flags 0x0
      12 ep0 at eisa0 slot -1 flags 0x0
      13 ep0 at pci* dev -1 function -1 flags 0x0
      14 ep* at isapnp0 port -1 size 0 iomem -1 iosiz 0 irq -1 drq -1 flags 0x0
      15 ep* at isa0 port -1 size 0 iomem -1 iosiz 0 irq -1 drq -1 drq2 -1 flags 0x0
      16 ep* at eisa0 slot -1 flags 0x0
      17 ep* at pci* dev -1 function -1 flags 0x0
      18 ep* at pcmcia* dev -1 irq -1 flags 0x0
     UKC> add ep1
     Clone Device (DevNo, 'q' or '?') ? 13
     Insert before Device (DevNo, 'q' or '?') 14
      14 ep1 at pci* dev -1 function -1
     UKC> change 14
      14 ep1 at pci* dev -1 function -1
     change (y/n) ? y
     dev [-1] ? 14
     function [-1] ?
     flags [0] ? 18
      14 ep1 changed
      14 ep1 at pci* dev 14 function -1 flags 0x12
     UKC>

     When configuration is completed, booting can proceed by issuing the quit
     or exit commands.

     UKC> quit
     Continuing...
     mainbus0 (root)

SEE ALSO
     config(8)

AUTHORS
     Mats O Jansson <moj@stacken.kth.se>

BUGS
     The add command is rather restricted, and might be expanded in the fu-
     ture.

OpenBSD 4.7                      May 31, 2007                                3
