This is the procedure to make an 'initrd' ramdisk with rescue tools for raid.
Specifically, this document referrs to a RAID1 implementation, however it is generally applicable to any raid scheme with a root mounted raid device.
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!!!
The first thing that must be done is to patch and build your kernel and become familiar with the raid tools. 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.
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.
You can download the Slackware distribution from:
ftp.cdrom.com/pub/linux/
If you already have Slackware, you only need to download new 'a', 'ap', and 'n' disksets.
I use loadlin to boot the kernel image and ramdisk from a dos partition. 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
/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.
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
associate the file with a loop device
and generate an ext2 file system on the file
losetup /dev/loop0 build
mke2fs -v -m0 -L initrd /dev/loop0
mount /dev/loop0 mnt
...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 xFrom the 'AP series, I use only 'JOE', and editor I like, and 'MC' a small and useful file management tool. You choose the utilities you will need on your system.
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 xFrom the 'N' package I only loaded TCPIP. This isn't really necessary, but is very handy and allows access to the network while working on a repair or update with the root raid array dismounted. TCPIP also contains 'biff' which is used by some of the applications in 'A'. If you don't install 'N' you might want to install the biff package anyway.
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 xWith the installation complete, say no to everything else (no to all configuration requests) and exit the script.
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
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 installNow!! the Makefile for install is not quite right so do the following to clean up. This will be fixed in future releases so that the re-linking will not be necessary.
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
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
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
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
associate the file with a loop device
and generate a ext2 file system on the file
losetup /dev/loop1 bare.fs
mke2fs -v -m0 -L initrd /dev/loop1
mount /dev/loop1 mnt2
Copy the 'build' file system to 'bare.fs'
cp -a mnt/* mnt2
Save the 'bare.fs' system before customization so later update is easy.
The 'build' file system is no longer needed and may be deleted.
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
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
Make sure your etc directory is clean of *~, core and log files.
The next 2 commands creates some warning messages, ignore them.
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
Edit the following files to correct them for your rescue system.
cd mnt
Non-network
etc/fstab comment out the mount of root and raid devices.
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 isread-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.
Create any directories for mounting /dev/disk... as may be required
that are unique to your system. Mine need:
cd /root/raidboot/mnt <--- initrd root
mkdir dosa dos partition mount point
mkdir dosc dos mirror mount point
The rescue file system is complete!
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!
To make the rescue disk boot the raid device, you need only copy the executable script file:
linuxrc
---------------------- linuxrc --------------------
#!/bin/sh
# ver 1.07 2-12-98
# mount the proc file system
/bin/mount /proc
# This may vary for your system.
# Mount the dos partitions, try both
# in case one disk is dead
/bin/mount /dosa
/bin/mount /dosc
# Set a flag in case the raid status file is not found
# then check both drives for the status file
RAIDOWN="raidstat.ro not found"
/bin/echo "Reading md0 shutdown status."
if [ -f /dosa/linux/raidstat.ro ]; then
RAIDOWN=`/bin/cat /dosa/linux/raidstat.ro`
RAIDREF=`/bin/cat /dosc/linux/raidgood.ref`
else
if [ -f /dosc/linux/raidstat.ro ]; then
RAIDOWN=`/bin/cat /dosc/linux/raidstat.ro`
RAIDREF=`/bin/cat /dosc/linux/raidgood.ref`
fi
fi
# Test for a clean shutdown with all disks operational
if [ "${RAIDOWN} != ${RAIDREF}" ]; then
echo "ERROR ${RAIDOWN}"
# Use the next 2 lines to BAIL OUT and leave rescue running
/bin/echo 0x100>/proc/sys/kernel/real-root-dev
exit # leaving the error files in dosa/linux,etc...
fi
# The raid array is clean, proceed by removing
# status file and writing a clean superblock
/bin/rm /dosa/linux/raidstat.ro
/bin/rm /dosc/linux/raidstat.ro
/sbin/mkraid /etc/raid1.conf -f --only-superblock
/bin/umount /dosa
/bin/umount /dosc
# Mount raid array
echo "Mounting md0, root filesystem"
/sbin/mdadd -ar
# If there are errors - BAIL OUT and leave rescue running
if [ $? -ne 0 ]; then
echo "RAID device has errors"
# Use the next 3 lines to BAIL OUT
/bin/rm /etc/mtab # remove bad mtab
/bin/echo 0x100>/proc/sys/kernel/real-root-dev
exit
fi
# else tell the kernel to switch to /dev/md0 as the /root device
# The 0x900 value the device number calculated by:
# 256*major_device_number + minor_device number
/bin/echo 0x900>/proc/sys/kernel/real-root-dev
# umount /proc to deallocate initrd device ram space
/bin/umount /proc
/bin/echo "/dev/md0 mounted as root"
exit
#------------------ end linuxrc ----------------------
Add 'linuxrc' to initrd boot device
cd /root/raidboot
chmod 777 linuxrc
cp -p linuxrc mnt
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
I have modified Bohumil Chalupa's raid stop work-around slightly. His original solution is presented in Appendix A.
Since there are no linux partitions left on the production system except md0, the dos partitions are used to store the raidOK readonly status. I chose to write a file to each dos partition 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 one of the hard drives dies.
I modified my rc.6 script to attempt dismount of the root raid1 array and any other raid device in mdtab. You may need slightly different scripts, but the basics should be the same. The complete rc.6 file is shown in Appendix B.
To capture the raid array shutdown status, just before the file systems are dismounted insert:
RAIDSTATUS=`/bin/cat /proc/mdstat | /usr/bin/grep md0`
After all the file systems are dismounted (the root file system
'will not' dismount) add:
# root device remains mounted RO
# mount dos file systems RW
mount -n -o remount,ro /
echo "Writing RAID read-only boot FLAG(s)."
mount -n /dosa
mount -n /dosc
# create raid mounted RO flag in duplicate
# containing the shutdown status of the raid array
echo ${RAIDSTATUS} > /dosa/linux/raidstat.ro
echo ${RAIDSTATUS} > /dosc/linux/raidstat.ro
umount -n /dosa
umount -n /dosc
# Stop all the raid arrays (except root)
echo "Stopping raid"
mdstop -a
This will cleanly stop all raid devices except root. Root status
is passed to the next boot in raidstat.ro.
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
Copy rescue.gz to your dos partition.
All that remains is to test the new file system by rebooting. See the loadlin parameters in my dos linux.bat file next.
The disks I chose for my system are much larger than those manageable by lilo. Therefore, I used loadlin to boot the system from a small dos partition with a mirror (copy) on the companion disk.
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:\linux.bat
c:\linux\loadlin.exe
c:\linux\zimage
c:\linux\rescue.gz
c:\linux\raidgood.ref
c:\linux\raidstat.ro (only at shutdown)
linux.bat contains:
---------------------- linux.bat ---------------------------
rem Sample DOS batch file to boot Linux.
rem Start the LOADLIN process:
rem c:\linux\loadlin c:\linux\zimage root=/dev/ram0 ro ramdisk_size=16384 initrd=c:\linux\rescue.gz mem=131072k
c:\linux\loadlin c:\linux\zimage root=/dev/md0 ro ramdisk_size=16384 initrd=c:\linux\rescue.gz mem=131072k
rem -- this is my development system -- it goes away later
rem c:\linux\loadlin c:\linux\zimage root=/dev/hda3 ro noinitrd mem=131072k
------------------------------------------------------------
***** >> 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 (this seems to fail sometimes, I don't know why, it works when the reset button is pushed but does not work with 'shutdown -r now').