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4. initrd Cookbook for root mounted RAID

This is the procedure to make an 'initrd' ramdisk with rescue tools for raid.

Specifically, this document referrs to RAID1 and RAID5 implementations.

4.1 Security Reminder

The rescue file system may be used stand alone. Should your raid array fail to mount, you are left with the rescue system mounted and running. TAKE THE APPROPRIATE SECURITY PRECAUTIONS!!!

4.2 Build the Kernel and Raid Tools

The first thing that must be done is to patch and build your kernel and become familiar with the raid tools. Make sure and include Gadi's raid stop patch in Appendix E. Configure, mount and test your raid device(s). The details of how to do this are included in the raidtools package and briefly reviewed later in this document.

4.3 Build the initrd Rescue and Boot filesystem

I used the Slackware-3.4 distribution to build both the Rescue/Boot filesystem and the filesystem for the production machine. Any linux distribution should work fine. If you use a different distribution, review the Slackware specific portion of this procedure and modify it to suit your needs.

I use loadlin to boot the kernel image and ramdisk from a dos partition simply because there are oddball devices in my system that have dos configuration software. Lilo will work just as well and a small linux partition can be used instead containing only the raid/boot files and the lilo record.

For the raid boot/rescue system, I chose to create a minimum ramdisk system using the Slackware 'setup' script followed by installing the 'linuxthreads' package and 'raidtools' over the clean Slackware installation on my ramdisk. I used the identical procedure to build the production system. So the rescue and production systems are very similar.

This installation process gives me a 'bare' system (save a copy of the file) to which I overlay

        /lib/modules/2.x.x......
        /etc .... with a modified fstab, mdtab, raidX.conf, raidboot.conf
        /etc/rc.d
        /dev/md*

from my current system to customize it for the particular kernel and machine that it is/will-be running on.

This makes the boot/rescue system the same system that is running on the root mounted raid device, just skinnyed down a bit, while allowing the library, etc... revisions to always be current.

4.4 Start the STEP by STEP instructions

From the root home directory (/root):

        cd /root
        mkdir raidboot
        cd raidboot

Create a mountpoints to work on

        mkdir mnt
        mkdir mnt2

Make a file large enough to do the file system install. This will be a lot larger than the final rescue file system. I chose 24 megs since 16 megs is not large enough

        dd if=/dev/zero of=build bs=1024k count=24

        losetup /dev/loop0 build
        mke2fs -v -m0 -L initrd /dev/loop0
        mount /dev/loop0 mnt

4.5 Install the distribution - Slackware Specific

...skip Slackware Specific stuff and go to next section.

Now that an empty filesystem is created and mounted, run "setup".

Specify         /root/raidboot/mnt

as the 'target'. The source is whatever you normally install from. Select the packages you wish to install and proceed but DO NOT configure.

Choose 'EXPERT' prompting mode.

I chose 'A', 'AP, and 'N' installing only the minimum to run the system plus an editor I am familiar with (vi, jed, joe) that is reasonably compact.

lqqqqqqqq SELECTING PACKAGES FROM SERIES A (BASE LINUX SYSTEM) qqqqqqqqk
x lqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqk x
x x   [X] aaa_base  Basic filesystem, shell, and utils - REQUIRED    x x
x x   [X] bash      GNU bash-1.14.7 shell - REQUIRED                 x x
x x   [X] devs      Device files found in /dev - REQUIRED            x x
x x   [X] etc       System config files & utilities - REQUIRED       x x
x x   [X] shadow    Shadow password suite - REQUIRED                 x x
x x   [ ] ide       Linux 2.0.30 no SCSI (YOU NEED 1 KERNEL)         x x
x x   [ ] scsi      Linux 2.0.30 with SCSI (YOU NEED 1 KERNEL)       x x
x x   [ ] modules   Modular Linux device drivers                     x x
x x   [ ] scsimods  Loadable SCSI device drivers                     x x
x x   [X] hdsetup   Slackware setup scripts - REQUIRED               x x
x x   [ ] lilo      Boots Linux (not UMSDOS), DOS, OS/2, etc.        x x
x x   [ ] bsdlpr    BSD lpr - printer spooling system                x x
x x   [ ] loadlin   Boots Linux (UMSDOS too!) from MS-DOS            x x
x x   [ ] pnp       Plug'n'Play configuration tool                   x x
x x   [ ] umsprogs  Utilities needed to use the UMSDOS filesystem    x x
x x   [X] sysvinit  System V-like INIT programs - REQUIRED           x x
x x   [X] bin       GNU fileutils 3.12, elvis, etc. - REQUIRED       x x
x x   [X] ldso      Dynamic linker/loader - REQUIRED                 x x
x x   [ ] ibcs2     Runs SCO/SysVr4 binaries                         x x
x x   [X] less      A text pager utility - REQUIRED                  x x
x x   [ ] pcmcia    PCMCIA card services support                     x x
x x   [ ] getty     Getty_ps 2.0.7e - OPTIONAL                       x x
x x   [X] gzip      The GNU zip compression - REQUIRED               x x
x x   [X] ps        Displays process info - REQUIRED                 x x
x x   [X] aoutlibs  a.out shared libs - RECOMMENDED                  x x
x x   [X] elflibs   The ELF shared C libraries - REQUIRED            x x
x x   [X] util      Util-linux utilities - REQUIRED                  x x
x x   [ ] minicom   Serial transfer and modem comm package           x x
x x   [ ] cpio      The GNU cpio backup/archiving utility            x x
x x   [X] e2fsbn    Utilities for the ext2 file system               x x
x x   [X] find      GNU findutils 4.1                                x x
x x   [X] grep      GNU grep 2.0                                     x x
x x   [ ] kbd       Change keyboard mappings                         x x
x x   [X] gpm       Cut and paste text with your mouse               x x
x x   [X] sh_utils  GNU sh-utils 1.16 - REQUIRED                     x x
x x   [X] sysklogd  Logs system and kernel messages                  x x
x x   [X] tar       GNU tar 1.12 - REQUIRED                          x x
x x   [ ] tcsh      Extended C shell version 6.07                    x x
x x   [X] txtutils  GNU textutils-1.22 - REQUIRED                    x x
x x   [ ] zoneinfo  Configures your time zone                        x x
x mqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj x

lqqqqqqqqq SELECTING PACKAGES FROM SERIES AP (APPLICATIONS) qqqqqqqqqk
x x     [ ] ispell    The International version of ispell          x x
x x     [ ] jove      Jonathan's Own Version of Emacs text editor  x x
x x     [ ] manpgs    More man pages (online documentation)        x x
x x     [ ] diff      GNU diffutils                                x x
x x     [ ] sudo      Allow special users limited root access      x x
x x     [ ] ghostscr  GNU Ghostscript version 3.33                 x x
x x     [ ] gsfonts1  Ghostscript fonts (part one)                 x x
x x     [ ] gsfonts2  Ghostscript fonts (part two)                 x x
x x     [ ] gsfonts3  Ghostscript fonts (part three)               x x
x x     [ ] jed       JED programmer's editor                      x x
x x     [X] joe       joe text editor, version 2.8                 x x
x x     [ ] jpeg      JPEG image compression utilities             x x
x x     [ ] bc        GNU bc - arbitrary precision math language   x x
x x     [ ] workbone  a text-based audio CD player                 x x
x x     [X] mc        The Midnight Commander file manager          x x
x x     [ ] mt_st     mt ported from BSD - controls tape drive     x x
x x     [ ] groff     GNU troff document formatting system         x x
x x     [ ] quota     User disk quota utilities                    x x
x x     [ ] sc        The 'sc' spreadsheet                         x x
x x     [ ] texinfo   GNU texinfo documentation system             x x
x x     [ ] vim       Improved vi clone                            x x
x x     [ ] ash       A small /bin/sh type shell - 62K             x x
x x     [ ] zsh       Zsh - a custom *nix shell                    x x
x mqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj x

lqqqq SELECTING PACKAGES FROM SERIES N (NETWORK/NEWS/MAIL/UUCP) qqqqqk
x lqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqk x
x x    [ ] apache    Apache WWW (HTTP) server                      x x
x x    [ ] procmail  Mail delivery/filtering utility               x x
x x    [ ] dip       Handles SLIP/CSLIP connections                x x
x x    [ ] ppp       Point-to-point protocol                       x x
x x    [ ] mailx     The mailx mailer                              x x
x x    [X] tcpip     TCP/IP networking programs                    x x
x x    [ ] bind      Berkeley Internet Name Domain server          x x
x x    [ ] rdist     Remote file distribution utility              x x
x x    [ ] lynx      Text-based World Wide Web browser             x x
x x    [ ] uucp      Taylor UUCP 1.06.1 with HDB && Taylor configs x x
x x    [ ] elm       Menu-driven user mail program                 x x
x x    [ ] pine      Pine menu-driven mail program                 x x
x x    [ ] sendmail  The sendmail mail transport agent             x x
x x    [ ] metamail  Metamail multimedia mail extensions           x x
x x    [ ] smailcfg  Extra configuration files for sendmail        x x
x x    [ ] cnews     Spools and transmits Usenet news              x x
x x    [ ] inn       InterNetNews news transport system            x x
x x    [ ] tin       The 'tin' news reader (local or NNTP)         x x
x x    [ ] trn       'trn' for /var/spool/news                     x x
x x    [ ] trn-nntp  'trn' for NNTP (install 1 'trn' maximum)      x x
x x    [ ] nn-spool  'nn' for /var/spool/news                      x x
x x    [ ] nn-nntp   'nn' for NNTP (install 1 'nn' maximum)        x x
x x    [ ] netpipes  Network pipe utilities                        x x
x mqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj x

4.6 Install linux pthreads

Now you must install the 'linuxthreads-0.71' library. I have included this diff for the linuxthreads Makefile rather than explain the details of the installation by hand. Save the original Makefile, apply the diff and then:

        cd /usr/src/linuxthreads-0.71
  patch
        make
        make install

-------------------diff Makefile.old  Makefile.raid-----------------
2a3,13
> # If you are building "linuxthreads" for installation on a mount
> # point which is not the "root" partition, redefine 'BUILDIR' to
> # the mount point to use as the "root" directory
> # You may wish to do this if you are building an 'initial ram disk'
> # such as used with bootable root raid devices.
> # REQUIRES ldconfig version 1.9.5 or better
> # do ldconfig -v to check
> #
> BUILDIR=/root/raidboot/mnt
> #BUILDIR=
> 
81,82c92,93
<       install pthread.h $(INCLUDEDIR)/pthread.h
<       install semaphore.h $(INCLUDEDIR)/semaphore.h
---
>       install pthread.h $(BUILDIR)$(INCLUDEDIR)/pthread.h
>       install semaphore.h $(BUILDIR)$(INCLUDEDIR)/semaphore.h
84c95
<       test -f /usr/include/sched.h || install sched.h $(INCLUDEDIR)/sched.h
---
>       test -f $(BUILDIR)/usr/include/sched.h || install sched.h $(BUILDIR)$(INCLUDEDIR)/sched.h
86,89c97,103
<       install $(LIB) $(LIBDIR)/$(LIB)
<       install $(SHLIB) $(SHAREDLIBDIR)/$(SHLIB)
<       rm -f $(LIBDIR)/$(SHLIB0)
<       ln -s $(SHAREDLIBDIR)/$(SHLIB) $(LIBDIR)/$(SHLIB0)
---
>       install $(LIB) $(BUILDIR)$(LIBDIR)/$(LIB)
>       install $(SHLIB) $(BUILDIR)$(SHAREDLIBDIR)/$(SHLIB)
>       rm -f $(BUILDIR)$(LIBDIR)/$(SHLIB0)
>       ln -s $(SHAREDLIBDIR)/$(SHLIB) $(BUILDIR)$(LIBDIR)/$(SHLIB0)
> ifneq ($(BUILDIR),)
>       ldconfig -r ${BUILDIR} -n $(SHAREDLIBDIR)
> else
91c105,106
<       cd man; $(MAKE) MANDIR=$(MANDIR) install
---
> endif
>       cd man; $(MAKE) MANDIR=$(BUILDIR)$(MANDIR) install

4.7 Install Raid Tools

The next step is the installation of the raid tools. raidtools-0.42

You must run the "configure" script to point the Makefile at the build directory for the ramdisk files

  cd /usr/src/raidtools-0.42
  configure --sbindir=/root/raidboot/mnt/sbin --prefix=/root/raidboot/mnt/usr
  make
  make install

Fix the make install error

The file links specified in the Makefile at 'LINKS' must be removed and re-linked to operate properly.

        cd /root/raidboot/mnt/sbin
        ln -fs mdadd mdrun
        ln -fs mdadd mdstop

4.8 Remove un-needed directories and files from new filesystem.

Delete the following directories from filesystem (CAUTION DON'T DELETE FROM YOUR RUNNING SYSTEM) it's easy to do, guess how I found out!!!

        cd /root/raidboot/mnt
        rm -r home/ftp/*
        rm -r lost+found
        rm -r usr/doc
        rm -r usr/info
        rm -r usr/local/man
        rm -r usr/man
        rm -r usr/openwin
        rm -r usr/share/locale
        rm -r usr/X*
        rm -r var/man
        rm -r var/log/packages
        rm -r var/log/setup
        rm -r var/log/disk_contents

4.9 Create /dev/mdx

The last step simply copies the /dev/md* devices from the current file system onto the rescue file system. You could create these with mknode.

        cp -a /dev/md* /root/raidboot/mnt/dev

4.10 Create a bare filesystem suitable for initrd

Now you have a clean re-useable filesystem ready for customization. Once customized, this file system can be used for rescue should the raid device(s) become corrupted and the raid tools needed to fix them. It will also be used to boot and root-mount the raid device by adding the linuxrc file which will be discussed next.

Copy the file system to a smaller device for the initrd file, 16 megs should be large enough.

Create the smaller file system and mount it

        cd /root/raidboot
        dd if=/dev/zero of=bare.fs bs=1024k count=16

        losetup /dev/loop1 bare.fs
        mke2fs -v -m0 -L initrd /dev/loop1
        mount /dev/loop1 mnt2

        cp -a mnt/* mnt2

        cd /root/raidboot
        umount mnt
        umount mnt2
        losetup -d /dev/loop0
        losetup -d /dev/loop1
        rm build
        cp bare.fs rescue
        gzip -9 bare.fs

Create the BOOT/RESCUE initrd filesystem

Now copy the system dependent items that match the kernel from the development platform, or you can manually modify the files in the rescue file system to match your target system.

        losetup /dev/loop0 rescue
        mount /dev/loop0 mnt

        cp -dp /etc/* mnt/etc
        cp -dp /etc/rc.d/* mnt/etc/rc.d

        mkdir  mnt/lib/modules
        cp -a  /lib/modules/2.x.x mnt/lib/modules <--- your current 2.x.x

Corrections for the Rescue System

Edit the following files to correct them for your rescue system. Some file names listed below are Slackware specific but have equivalents in other distributions.

        cd mnt

Non-network
        etc/fstab
        etc/mdtab       should work OK
Network
        etc/hosts
        etc/resolv.conf 
        etc/hosts.equiv         and related files
        etc/rc.d/rc.inet1       correct ip#, mask, gateway, etc...
        etc/rc.d/rc.S           remove entire section on file system status
                from:
                        # Test to see if the root partition is read-only
                to but not including:
                        # remove /etc/mtab* so that mount will .....
                                This avoids the annoying warning that
                                the ramdisk is mounted rw.
        etc/rc.d/rc.xxxxx       others as required, see later on in this doc
        root/.rhosts            if present
        home/xxxx/xxxx          others as required

    WARNING:    The above procedure moves your password and shadow
                files onto the rescue disk!!!!!

    WARNING:    You may not wish to do this for security reasons.

        cd /root/raidboot/mnt           <--- initrd root
        mkdir dosa                      dos partition mount point
        mkdir dosb                      dos mirror mount point

You will note upon examination of the files in the rescue file system, that there are still many files that could be deleted. I have not done this since it would overly complicate this procedure and most raid systems have adequate disk and memory. If you wish to skinny down the file system, go to it!

4.11 Making 'initrd' boot the RAID device - linuxrc

To make the rescue disk boot the raid device, you need only copy the executable script file:

linuxrc

to the root of the device.

The theory of operation for this linuxrc file is discussed in Appendix G, linuxrc theory of operation.

A very simple and much easier to understand (working) linuxrc is included in Appendix D, obsolete linuxrc and shutdown scripts. Copy the following text to linuxrc and save in your development area.

 -------------------- linuxrc ----------------------
#!/bin/sh
# ver 1.13 3-6-98
#
################# BEGIN 'linuxrc' ##################
#                DEFINE FUNCTIONS                  #
####################################################
# Define 'Fault' function in the event something 
# goes wrong during the execution of 'linuxrc'
#
FaultExit () {
# correct fstab to show '/dev/ram0' for rescue system
    /bin/cat /etc/fstab | {
    while read Line
    do  
        if [ -z "$( echo ${Line} | /usr/bin/grep md0 )" ]; then
            echo ${Line}
        else
            echo "/dev/ram0 / ext2 defaults 1 1"
        fi
    done
    } > /etc/tmp.$$
    /bin/mv /etc/tmp.$$ /etc/fstab
#       point root at /dev/ram0 (the rescue system)
        echo 0x100>/proc/sys/kernel/real-root-dev
        /bin/umount /proc
        exit
}

# Define 'Warning' procdure to print banner on boot terminal
#
Warning () {
    echo '*********************************'
    echo -e " $*"
    echo '*********************************'
}

# Define 'SplitKernelArg' to help extract 'Raid' related kernel arguments
SplitKernelArg () { eval $1='$( IFS=,; echo $2)' }

#Define 'SplitConfArgs' to help extract system configuration arguments
SplitConfArgs () {
    RaidBootType=$1
    RaidBootDevice=$2
    RaidConfigPath=$3
}
########################################################
################### MAIN linuxrc #######################
########################################################
# mount the proc file system
/bin/mount /proc

# Get the boot partition and configuration location from command line
CMDLINE=`/bin/cat /proc/cmdline`
for Parameter in $CMDLINE; do
    Parameter=$( IFS='='; echo ${Parameter} )
    case $Parameter in
        Raid*) SplitKernelArg $Parameter;;
    esac
done

# check for 'required raid boot'
if [ -z "${Raid_Conf}" ]; then
    Warning Kernel command line \'Raid_Conf\' missing
    FaultExit
fi
SplitConfArgs $Raid_Conf

# tmp mount the boot partition
/bin/mount -t ${RaidBootType} ${RaidBootDevice} /mnt

# get etc files from primary raid system
pushd /etc

# this will un-tar into 'etc' (see rc.6)
if [ ! -f /mnt/${RaidConfigPath}/raidboot.etc ]; then
# bad news, this file should be here
    Warning required file \'raidboot.etc\' \
    missing from ${RaidBootDevice}/${RaidConfigPath} \\n \
    \\tUsing rescue system defaults
else
    /bin/tar -xf /mnt/${RaidConfigPath}/raidboot.etc
fi
# get 'real' raidboot device for this boot
# status path, and name of raidX.conf
if [ ! -f /mnt/${RaidConfigPath}/raidboot.cfg ]; then
# bad news, this file should be here
    Warning required file 'raidboot.cfg' \
    missing from ${RaidBootDevice}/${RaidConfigPath}\\n \
    \\tUsing rescue system defaults
# Get the first raidX.conf file name in $RArg1
    RaidBootDevs=$RaidBootDevice
    RaidStatusPath=$RaidConfigPath
    for RaidConfigEtc in $( ls raid*.conf )
    do break; done
else
    {
    read RaidBootDevs
    read RaidStatusPath
    read RaidConfigEtc
    } < /mnt/${RaidConfigPath}/raidboot.cfg

fi
popd
/bin/umount /mnt

# Set a flag in case the raid status file is not found
#
RAIDOWN="raidboot.ro not found"
RAIDREF="raidgood.ref not found"
echo "Reading md0 shutdown status."

# search for raid shutdown status
for Device in ${RaidBootDevs}
do
#   these filesystem types should be in 'fstab' since
#   the partitions must be mounted for a clean raid shutdown
    /bin/mount ${Device} /mnt
    if [ -f /mnt/${RaidStatusPath}/raidboot.ro ]; then
        RAIDOWN=`/bin/cat /mnt/${RaidStatusPath}/raidboot.ro`
        RAIDREF=`/bin/cat /mnt/${RaidStatusPath}/raidgood.ref`
        /bin/umount /mnt
        break
    fi
    /bin/umount /mnt
done
# Test for a clean shutdown with array matching reference
if [ "${RAIDOWN}" != "${RAIDREF}" ]; then
    Warning shutdown ERROR ${RAIDOWN}
    FaultExit
fi

# The raid array is clean, remove shutdown status files
for Device in ${RaidBootDevs}
do
    /bin/mount ${Device} /mnt
    /bin/rm -f /mnt/${RaidStatusPath}/raidboot.ro
    /bin/umount /mnt
done

# Write a clean superblock on all raid devices

echo "write clean superblocks"
/sbin/mkraid -f --only-superblock /etc/${RaidConfigEtc}

# Activate raid array(s)
if [ -z "$Raid_ALT" ]; then
    /sbin/mdadd -ar
else
    /sbin/mdadd $Raid_ALT
fi

#  If there are errors - BAIL OUT and leave rescue running
if [ $? -ne 0 ]; then
   Warning some RAID device has errors
   FaultExit
fi

# Everything is fine, let the kernel mount /dev/md0
# tell the kernel to switch to /dev/md0 as the /root device
# The 0x900 value is the device number calculated by:
#  256*major_device_number + minor_device number
echo "/dev/md0 mounted on root"
echo 0x900>/proc/sys/kernel/real-root-dev
# umount /proc to deallocate initrd device ram space
/bin/umount /proc
exit
#------------------ end linuxrc ----------------------

        cd /root/raidboot
        chmod 777 linuxrc
        cp -p linuxrc mnt

4.12 Modifying the rc-scripts for SHUTDOWN

To complete the installation, modify the rc scripts to save the md status to the real root device when shutdown occurs.

In slackware this is rc.0 -> rc.6
In debian 'bo' this is in both 'halt' and 'reboot'

If you implement this in another distribution, please e-mail
the instructions and sample files so they can be included here.

Since there are no linux partitions left on the production system except md0, the boot partitions are used to store the raidOK readonly status. I chose to write a file to each of the duplicate boot partitions containing the status of the md array at shutdown and signifying that the md device has been remounted RO. This allows the system to be fail safe when any of the hard drives die.

The shutdown script is modified to call rc.raidown which saves the necessary information to successfully reboot and mount the raid device. Examples of shutdown scripts for various linux distributions are shown in Appendix B.

To capture the raid array shutdown status insert a call to rc.raidown after any case statements (if present) but before the actual shutdown (kills, status saves, etc...) begins and before the file systems are dismounted.

############ Save raid boot and status info ##############
#
  if [ -x /etc/rc.d/rc.raidown ]; then
    /etc/rc.d/rc.raidown
  fi
################## end raid boot #########################

################ for raid arrays #########################
# Stop all known raid arrays (except root which won't stop)
  if [ -x /sbin/mdstop ]; then
    echo "Stopping raid"
    /sbin/mdstop -a
  fi
##########################################################

Copy the rc file to your new raid array, the rescue file system that is still mounted on /root/raidboot/mnt and the development system if it is on the same machine.

Modify rescue etc/fstab as needed and make sure rescue mdtab is correct.

Now copy the rescue disk to your dos partition and everything should be ready to boot the raid device as root.

        umount mnt
        losetup -d /dev/loop0
        gzip -9 rescue

All that remains is to creat the configuration file raidboot.conf and test the new file system by rebooting.

4.13 Configuring RAIDBOOT - raidboot.conf

The comments following the example configuration file explain each of the three lines. This example file is for a 4 drive raid5 scsii array with duplicate boot partitions on drives sda1 and sdb1. Put the paramaters descriptive of your file systems here instead.

  /dev/sda1 /dev/sdb1
  linux
  raid5.conf
# comments may only be placed 'after' the three
# configuration lines.
#
# This is 'raidboot.conf'
#
# line one, the partition(s) containing the 'initrd' raid-rescue system
#       It is not necessary to boot from these partitions, however,
#       since the rescue system will not fit on floppy, it is necessary
#       to know which partitions are to be used to load the rescue system
#
# line two, the path to the raidboot config information
#       Where the shutdown status, etc... is located at boot time
#       It does NOT include the mount point information, only 'path'
#       /mntpoint/'path'
#
# line -3-, name of the raid configuration file
#       Current raid configuration file i.e. raid1.conf, raid5.conf

4.14 Kernel 'loadlin and lilo' variables for RESCUE and RAID

There are two kernel variables for the RESCUE and RAID system, only the first need be specified.

• Raid_Conf=msdos,/dev/sda1,raidboot

  This variable points to raid boot device and configuration file. For floppy rescue boot, you may want to specify this on the kernel command line or in the loadlin or lilo boot file

  format: 'filesystem-type,device,path-to-config-from-mountpoint'

• Raid_ALT=-r,-p5,/dev/md0,/dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3

  Alternate mdadd parameters necessary when booting with non-redundant raid array. These are the comma separated command line parameters for mdadd. Unless they are needed to start a failed/non-redundant array, COMMENT OUT OR SPECIFY WITH A 'NULL'.

  i.e. Raid_ALT=

When booting with lilo, the parameters are included in the lilo config file in the form:

append="Raid_Conf=msdos,/dev/sda1,raidboot"
append="Raid_ALT=-r,-p5,/dev/md0,/dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3"

Since I have some hardware that requires DOS configuration utilities, I have a small dos partition on the system. Therefore, I used loadlin to boot the raid5 system from the dos partition with a mirror (copy) on the companion disk. An identical method is used for the raid1 system. The example below uses loadlin, but the procedure is very similar for lilo.

My dos root system contains a small editor among the utilities so I can modify the boot parameters of loadlin if necessary, allowing me to reboot the linux system on my swap disk while testing.

The dos system contains this tree for linux"

        c:\raidboot.bat
        c:\raidboot\loadlin.exe
        c:\raidboot\zimage
        c:\raidboot\rescue.gz
        c:\raidboot\raidboot.cfg
        c:\raidboot\raidboot.etc
        c:\raidboot\raidgood.ref
        c:\raidboot\raidstat.ro (only at shutdown)

---------------------- linux.bat ---------------------------
echo "Start the LOADLIN process:"
c:\raidboot\loadlin @c:\raidboot\boot.par
-------------------- end linux.bat -------------------------

        # loadlin boot parameter file
        #
        # version 1.02 3-6-98

        # linux kernel image
        c:\linux\zimage

        # target root device
        root=/dev/md0
        #root=/dev/ram0
        #root=/dev/sdc5

        # mount root device as 'ro'
        ro

        # size of ram disk
        ramdisk_size=16384

        # initrd file name
        initrd=c:\raidboot\rescue.gz
        #noinitrd

        # memory ends here
        mem=131072k

        # points to raid boot device, configuration file
        # for floppy rescue boot, you may want to specify 
        # this on the command line instead of here
        # format 'filesystem-type,device,path-to-config-frm_mntpnt'
        Raid_Conf=msdos,/dev/sda1,raidboot

        # Alternate mdadd parameters
        # necessary when boot with non-redundant raid
        # otherwise, COMMENT OUT OR SPECIFY 'NULL'
        #Raid_ALT=-r,-p5,/dev/md0,/dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3

        # ethernet devices
        ether=10,0x300,eth0

***** >> NOTE!! the only difference between forcing the rescue system to
            run and the raid device mounting, is the loadlin parameter

                root=/dev/ram0          for the rescue system
                root=/dev/md0           for RAID

                With root=/dev/ram0 the RAID device will not mount
                and the rescue system will run unconditionally.

If the RAID array fails, the rescue system is left mounted and running.

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