167 lines
3.6 KiB
Groff
167 lines
3.6 KiB
Groff
.\" Copyright 1992, 1993 Rickard E. Faith (faith@cs.unc.edu)
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.\" May be distributed under the GNU General Public License
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.\" Changes from sct@dcs.ed.ac.uk added Sat Oct 9 09:54:00 1993.
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.TH RDEV 8 "20 November 1993" "Linux 0.99" "Linux Programmer's Manual"
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.SH NAME
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rdev \- query/set image root device, swap device, RAM disk size, or video mode
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.SH SYNOPSIS
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.nf
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.BR "rdev [ \-rsvh ] [ \-o " offset " ] [ " image " [ " value " [ " offset " ] ] ]"
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.BR "rdev [ \-o " offset " ] [ " image " [ " root_device " [ " offset " ] ] ]"
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.BR "swapdev [ \-o " offset " ] [ " image " [ " swap_device " [ " offset " ] ] ]"
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.BR "ramsize [ \-o " offset " ] [ " image " [ " size " [ " offset " ] ] ]"
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.BR "vidmode [ \-o " offset " ] [ " image " [ " mode " [ " offset " ] ] ]"
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.BR "rootflags [ \-o " offset " ] [ " image " [ " flags " [ " offset " ] ] ]"
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.fi
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.SH DESCRIPTION
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.\" " for emacs hilit19
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With no arguments,
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.B rdev
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outputs an
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.I /etc/mtab
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line for the current root file system.
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With no arguments,
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.BR swapdev ", " ramsize ", " vidmode ", and " rootflags
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print usage information.
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In a bootable image for the Linux kernel, there are several pairs of bytes
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which specify the root device, the video mode, the size of the RAM disk,
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and the swap device. These pairs of bytes, by default, begin at offset 504
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(decimal) in the kernel image:
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.nf
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.RS
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498 Root flags
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(500 and 502 Reserved)
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504 RAM Disk Size
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506 VGA Mode
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508 Root Device
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(510 Boot Signature)
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.RE
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.fi
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.B rdev
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will change these values.
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Typical values for the
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.I image
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parameter, which is a bootable Linux kernel image, might be:
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.nf
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.RS
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/vmlinux
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/vmunix
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/boot/bzImage-2.4.0
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/dev/fd0
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/dev/fd1
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.RE
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.fi
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When using the
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.BR rdev ", or " swapdev
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commands, the
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.IR root_device " or " swap_device
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parameter might be something like:
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.nf
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.RS
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/dev/hda1
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/dev/hdf13
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/dev/sda2
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/dev/sdc4
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/dev/ida/c0d0p1
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.RE
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.fi
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For the
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.B ramsize
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command, the
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.B size
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parameter specifies the size of the RAM disk in kilobytes.
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For the
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.B rootflags
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command, the
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.B flags
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parameter contains extra information used when mounting root.
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Currently the only effect of these flags is to force the kernel to
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mount the root filesystem in readonly mode if
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.B flags
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is non-zero.
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For the
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.B vidmode
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command, the
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.B mode
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parameter specifies the video mode:
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.nf
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.RS
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-3 = Prompt
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-2 = Extended VGA
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-1 = Normal VGA
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0 = as if "0" was pressed at the prompt
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1 = as if "1" was pressed at the prompt
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2 = as if "2" was pressed at the prompt
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n = as if "n" was pressed at the prompt
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.RE
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.fi
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If the
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.I value
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is not specified, the
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.I image
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will be examined to determine the current settings.
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.SH OPTIONS
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.TP
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.B \-s
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Causes
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.B rdev
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to act like
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.BR swapdev .
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.TP
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.B \-r
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Causes
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.B rdev
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to act like
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.BR ramsize .
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.TP
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.B \-R
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Causes
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.B rdev
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to act like
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.BR rootflags .
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.TP
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.B \-v
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Causes
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.B rdev
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to act like
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.BR vidmode .
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.TP
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.B \-h
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Provides help.
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.SH BUGS
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For historical reasons, there are two methods for specifying alternative
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values for the offset.
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.sp
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The user interface is cumbersome, non-intuitive, and should probably be
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re-written from scratch, allowing multiple kernel image parameters to be
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changed or examined with a single command.
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.sp
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If LILO is used,
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.B rdev
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is no longer needed for setting the root device and the VGA mode, since
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these parameters that
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.B rdev
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modifies can be set from the LILO prompt during a boot. However,
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.B rdev
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is still needed at this time for setting the RAM disk size. Users are
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encouraged to find the LILO documentation for more information, and to use
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LILO when booting their systems.
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.SH AUTHORS
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.nf
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Originally by Werner Almesberger (almesber@nessie.cs.id.ethz.ch)
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Modified by Peter MacDonald (pmacdona@sanjuan.UVic.CA)
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rootflags support added by Stephen Tweedie (sct@dcs.ed.ac.uk)
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.fi
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