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NAME    [Toc]    [Back]

     boot, boot.conf - i386-specific second-stage bootstrap

DESCRIPTION    [Toc]    [Back]

     The main purpose of this program is to load the system  kernel while dealing
 with the downfalls of the PC BIOS architecture.

     As  described in boot_i386(8), this program is loaded by the
     primary bootstrap loader and provides a  convenient  way  to
load the kernel.
   This  program acts as an enhanced boot monitor for PC
systems, providing
 a common interface for the kernel to start from.

     Basic operations include:

     +o   Detecting and switching between multiple consoles.
     +o   Loading kernels from any device supported by your system
     +o   Loading kernels compressed by gzip(1).
     +o    Passing  system parameters queried from the BIOS to the
     +o   Providing an interactive command line.

     The sequence of its operation is as follows: initialization,
parsing the
     configuration file, then an interactive command line.  While
at the command
 line you have 5 seconds to type any commands, if  needed.  If time
     expires,  the kernel will be loaded according to the current
variable settings
 (see the set command).  Each time a kernel load fails,
the timeout
     is increased by one second.  The sequence of boot operations
is as follows:

     1.   Set up a protected mode environment which  catches  and
reports processor
  exceptions and provides a simple protected-mode
BIOS interface.

     2.   Probe for console devices, which includes the (default)
PC VGA+Keyboard
  console  (pc0)  and  up  to four serial consoles
(com0 through
          com3) connected to the serial ports.  Display  messages
to the default
 console about the devices found.

     3.    Detect  memory.   Conventional  memory  is detected by
querying the
          BIOS.  Extended memory is detected by probing  page-bypage through
          the  address  space,  rather than asking the BIOS; many
BIOS's cannot
          report larger than 64M of memory.  All memory found  is
reported to
          the default console device.

     4.    Probe  for APM support in the BIOS.  Display a message
if support is

     5.   If the file /etc/boot.conf  exists  on  the  filesystem
boot was loaded
          from,  open  and  parse  it.  This file may contain any
commands boot
          accepts at the interactive prompt.  Though default settings usually
          suffice, they can be changed here.

     6.   The header line

                >> OpenBSD/i386 BOOT [x.xx]

          is  displayed  to the active console, where x.xx is the
version number
          of the boot program, followed by the


          prompt, which means you are in interactive mode and may
enter commands.
   If  you  do not, boot will proceed to load the
kernel with the
          current parameters after the  timeout  period  has  expired.

     By  default,  boot  attempts  to  load the kernel executable
/bsd.  If that
     fails, it will attempt to load /obsd and then /bsd.old.   If
it fails to
     find any of these files, and no alternative kernel image has
been specified,
 the system will be unable to boot.

COMMANDS    [Toc]    [Back]

     The following commands are accepted at the boot prompt:

     boot [image [-acds]]
              Boots the kernel image specified by image with  any
options given.
    Image   specification  consists  of  a  pair
device:filename; either
 or both can be omitted (`:' is not  needed  if
both are omitted),
 in which case values from boot variables will
be used.

              When selecting the device to boot from, boot  makes
no distinction
 between SCSI and IDE type drives; they are detected as `hd'
              devices.  Therefore, to boot kernel /bsd from slice
`a' on the
              first  hard  drive  (irrespective  of device type),
specify ``boot

              -a   Causes the kernel to ask for the  root  device
to use.

              -c    Causes  the  kernel to go into boot_config(8)
before performing
 autoconf(4) procedures.

              -d   Causes the kernel to drop into ddb(4)  at  the
earliest convenient

              -s   Causes the kernel to boot single-user.

     echo [args]
              Displays args on the console device.

     help     Prints a list of available commands and machine dependent commands,
 if any.

     machine [command]
              Issues machine-dependent commands.  These  are  defined for i386

              diskinfo   Prints a list of hard disks installed on
your system
                        including: BIOS device  number,  and  the
BIOS geometry.

              memory     If  used without any arguments this command will print
                        out the memory  configuration  as  determined through
                        BIOS  routines.   Otherwise the arguments
would specify
                        the expressions to modify the memory configuration.
                        The expression would have a form of:


                        Meaning to add(+) or exempt(-) the specified by the
                        <size> amount of memory at  the  location
specified by
                        the  <address>  argument.   Both size and
base address
                        could be specified as octal, decimal,  or
                        numbers,  as  accepted  by the strtoul(3)
routine.  Memory
 segments are not required to be  adjacent to each
                        other, the only requirement is that there
is real
                        physical memory under  the  range  added.
For example:

                              machine mem +0x2000000@0x1000000

                        would  add  32M of memory right after the
first 16M.
                        The other  useful  command  would  be  to
withdraw a range
                        of  memory from OS usage (might be wrongfully reported
                        as useful by the BIOS).

                              machine mem -0x100000@0xf00000

                        which effectively excludes  15-16M  range
from the map
                        of useful memory.

              regs      Prints contents of processor registers if
                        with DEBUG.

     ls [directory]
              Prints contents of the specified directory in  long
format including:
  attributes  and  file type, owner, group,
size, filename.

     reboot   Reboots the machine by initiating a warm boot  procedure.

     set [varname [value]]
              If  invoked  without  arguments,  prints  a list of
variables and
              their values.  If only varname is  specified,  displays contents
              of  that  variable.   If varname and value are both
specified, sets
              that variable to the given  value.   Variables  include:

              addr     Address at which to load the kernel.
              debug    Debug flag if boot was compiled with DEBUG
              device   Boot device name (e.g., fd0a, hd0a).
              howto    Options to pass to the loaded kernel.
              image    File name containing the kernel image.
              timeout  Number of seconds boot will wait for human
                       before booting the default kernel image.
              tty       Active  console  device name (e.g., com0,
com1, pc0).
                       Currently,  only  the  first  serial  port
(com0) is supported
 for console on i386.

     stty [device [speed]]
              Displays  or  sets  the speed for a console device.
If changing
              the baudrate for the currently active console, boot
offers you
              five  seconds  of  grace time before committing the
change to allow
              you to change your terminal's speed to  match.   If
changing speed
              not for the active console, the baudrate is set for
the next
              time you switch to a serial console.  The  baudrate
value is not
              used for the pc0 console.

              The default baudrate is 9600bps.

     time     Displays system time and date.

FILES    [Toc]    [Back]

     /usr/mdec/biosboot    first stage bootstrap
     /usr/mdec/pxeboot     PXE bootstrap
     /boot                 system bootstrap
     /etc/boot.conf        system bootstrap's startup file
     /bsd                  kernel image

EXAMPLES    [Toc]    [Back]

     Boot the default kernel:

           boot> boot

     Remove  the 5 second pause at boot-time permanently, causing
boot to load
     the kernel immediately without prompting:

           # echo "boot" > /etc/boot.conf

     Use serial console.  A null modem cable should  connect  the
specified serial
 port to a terminal.  Useful for debugging.

           boot> set tty com0

     Invoke the serial console at every boot:

           # echo "set tty com0" > /etc/boot.conf

     Boot  the  kernel  named  /bsd  from the second hard disk in
``User Kernel
     Configuration'' mode (see boot_config(8)).   This  mechanism
allows for the
     explicit  enabling  and disabling of devices during the current boot sequence,
 as well as the modification  of  device  parameters.
Once booted,
     such  changes  can be made permanent by using config(8)'s -e

           boot> boot hd1a:/bsd -c

SEE ALSO    [Toc]    [Back]

     gzip(1), autoconf(4), ddb(4),  biosboot(8),  boot_config(8),
     fdisk(8), installboot(8), pxeboot(8), reboot(8)

     RFC 1950 describes the zlib library interface.

     The  official home page for the version of zlib used in this
     system is at http://quest.jpl.nasa.gov/zlib/.

HISTORY    [Toc]    [Back]

     This program was written by Michael  Shalayeff  for  OpenBSD

OpenBSD      3.6                        September     1,     1997
[ Back ]
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