130 lines
5.9 KiB
HTML
130 lines
5.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
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<html> <head>
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<title>Yet Another Rescue Disk</title>
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<body BGCOLOR="#ffefd5" TEXT="#483d8b">
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<H4>
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"Linux Gazette...<I>making Linux just a little more fun!</I>
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"</H4>
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<P> <HR> <P>
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<!--===================================================================-->
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<center><h1>The YARD Rescue Disk Package</h1></center>
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<center><h4><a href="mailto: layers@vax2.rainis.net">by Larry
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Ayers</a></h4></center>
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<center>Copyright (c) 1996</center><BR>
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<center><H5>Published in Issue 12 of the Linux Gazette</H5></center>
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<hr>
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<center><h3>Introduction</h3></center>
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<p>It is a common practice to use the rescue/boot disks supplied with a Linux
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distribution if filesystem problems occur and you need to boot from a floppy.
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Typically these disks consist of a bootable compressed kernel on disk 1, with
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the second disk containing basic maintenance tools such as fsck.
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<p>On the few occasions I've had to boot from such disks the transition from
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my familiar Linux environment to the bare-essentials, limited boot-disk system
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(constrained by the size of a floppy disk) has been disconcerting, to say the
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least. Typically if an editor is available it's a small one with which I've
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never worked, and many of the tools I'm used to having around aren't there.
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<p>Recently <a href="mailto: fawcett@nynexst.com">Tom Fawcett</a> has been
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refining a suite of customizable Perl scripts which make the creation of
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boot-disks from scratch easier. YARD (for Yet Another Rescue Disk) makes use
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of (and requires) the optional Linux kernel compressed ramdisk option, which
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allows you to load a compressed disk image into memory at boot-up. Paul
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Gortmaker has written a lucid explanation of the new ramdisk options in the
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file "ramdisk.txt", which is in the Documentation subdirectory of recent
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kernel source releases.
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<center><h3>Installation and Usage</h3></center>
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<p>The Yard distribution contains two files which need to be edited as a first
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step. <i>Config.pl</i> is a Perl script which sets such preferences as the
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type of floppy you're using and whether you are making a single boot-disk or a
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double. The <i>Bootdisk_Contents</i> file contains a list of all of the files
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and utilities you would like on your disk(s). This file needs to be edited
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heavily, as it includes much more than will fit on even two disks. Anything
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you like can be included in this file.
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<p>The next step is to run the Perl script <i>make_root_fs</i>. This script
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gathers up all of the files you've specified (as well as all libraries upon
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which they depend) and constructs a root filesystem upon whichever device was
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specified in the <i>Config.pl</i> script. A ramdisk works well. The new
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filesystem is then compressed with gzip into a single file in your /tmp
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directory. Once this process is complete yet another Perl script,
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<i>check_root_fs</i> is run, which makes sure that all needed
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libraries,etc. are present.
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<p>After all of this preparation you're ready to actually write the rescue
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disks; here's where you find out if you've attempted to cram too much into
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them. The <i>write_rescue_disk</i> script first copies your compressed kernel
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(vmlinuz) onto the disk (the first disk if it's a two-disk set) and then
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copies the compressed filesystem image you've constructed onto whatever is
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left. It took me several tries to pare down what I wanted Initially on the
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disks to what would actually fit. The virtue of the Yard system is that all
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you need to do to try again is re-edit the <i>Bootdisk_Contents</i> file and
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re-make the filesystem. Yard also writes log-files which can be helpful in
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diagnosing problems.
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<p>Modular kernels are great, but if you boot a kernel image and a capability
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you need is a demand-loaded module you're out of luck. Yard sidesteps this
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potential problem by including your modules directory in the compressed
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filesystem, as well as making sure that the kernel-daemon /sbin/kerneld is
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started at boot-up.
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<p>The result of this process is a customized miniature Linux system. It's a
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nice feeling to know that if your filesystem is in shambles due to a power
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outage or a beta program run amuck that you at least have familiar tools
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available.
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<p>Once you've managed to edit a set of Yard configuration files which will
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successfully write working rescue disks, consider saving copies of these files
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in case the disks become corrupted. I just replaced the supplied files with
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my edited copies, then tarred and gzipped the Yard distribution and saved it
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to floppy.
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<center><h3>Caveats</h3></center>
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<p>Yard gives you the option of using or not using Lilo to boot your disks. I
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first tried Yard with Lilo, as Lilo has always worked well for me. It
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wouldn't work with my Yard disks, so I disabled that option. I'm using an old
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version of Lilo, left over from my original Slackware 3.00 Linux installation,
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which may explain this failure. Yard works fine without it. Lilo might be
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necessary if you need to include parameters in order to boot your system, such
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as those required for some SCSI hard disks.
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<center><h3>Availability</h3></center>
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<p>Yard is available from <a href="http://www.cs.umass.edu/~fawcett/">the Yard
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home-page</a>, as well as from the sunsite archive and its mirrors. It's well
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worth trying if you want the ultimate in control over just what is included on
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your rescue disks.
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<hr>
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<address><a href="http://vax2.rain.gen.mo.us/~layers/">Larry Ayers<layers@vax2.rain.gen.mo.us></a></address>
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<!-- hhmts start -->
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Last modified: Wed Nov 20 09:21:50 CST 1996
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