# Boot + Root + Raid + Lilo : Software Raid mini-HOWTO

## Michael Robinton, Michael@BizSystems.com

v1.04, July 20, 2000

This document provides a cookbook for setting up root raid using the 0.90 raidtools for bootable raid mounted on root using standard LILO. Also covered is the conversion of a conventional disk to a raid1 or raid5 mirror set without the loss of data on the original disk.

## 1. Introduction

- 1.1 Acknowledgements
- 1.2 Bugs
- 1.3 Copyright Notice

## 2. What you need BEFORE YOU START

- 2.1 Required Packages
- 2.2 Where to get Up-to-date copies of this document.
- 2.3 Documentation -- Recommended Reading
- 2.4 RAID resources

## 3. Bootable Raid

- 3.1 Booting RAID 1 with standard LILO
- 3.2 Detailed explaination of lilo.conf for raid boot

## 4. Upgrading from non-raid to RAID1/4/5

- 4.1 Step 1 - prepare a new kernel
- 4.2 Step 2 - set up raidtab for your new raid.
- 4.3 Create, format, and configure RAID
- 4.4 Copy the current OS to the new raid device
- 4.5 Test your new RAID
- 4.6 Integrate old disk into raid array

## 5. Appendix A. - example raidtab

## 6. Appendix B. - SCSI reference implementation RAID5

## 7. Appendix C. - ide RAID10 with initrd

## 8. Appendix D. - ide RAID1-10 with initrd

## 1. Introduction

## 1.1 Acknowledgements

The essence of the information I've put together here was originally provided by Harald Nordgård-Hansen `<` hnh@bukharin.hiof.no `>` and posted to the raid mail list in a lilo.conf file with commentary by Martin Bene `<` mb@sime.com `>`. Many thanks for your contribution. I've tried to put this information and the helpful work of many others who contribute to the raid mail list and linux raid project into a COOKBOOK form, including many examples from real systems so that bootable root raid is easy to set up and understand. One section is devoted to the conversion of a standard single drive system to RAID. The key to the conversion, in my humble opinion, is the understanding of bootable root raid.

## 1.2 Bugs

Yes, I'm sure there are some. If you'd be good enough to report them, I will correct the document. ;-)

## 1.3 Copyright Notice

This document is GNU copyleft by Michael Robinton Michael@BizSystems.com.

Permission to use, copy, distribute this document for any purpose is hereby granted, provided that the author's / editor's name and this notice appear in all copies and/or supporting documents; and that an unmodified version of this document is made freely available. This document is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY, either expressed or implied. While every effort has been taken to ensure the accuracy of the information documented herein, the author / editor / maintainer assumes NO RESPONSIBILITY for any errors, or for any damages, direct or consequential, as a result of the use of the information documented herein.

## 2. What you need BEFORE YOU START

The packages you need and the documentation that answers the most common questions about setting up and running raid are listed below. Please review them throughly.

## 2.1 Required Packages

You need to obtain the most recent versions of these packages.

- a linux kernel that supports raid, initrd

  > I used linux-2.2.14 from kernel.org

- ftp://ftp.kernel.org/pub/linux/daemons/raid/alpha/ the most recent tools and patch that adds support for modern raid1/4/5

  > I used http://people.redhat.com/mingo/raid-patches/

## 2.2 Where to get Up-to-date copies of this document.

Click here to browse the author's latest version of this document. Corrections and suggestions welcome!

Boot Root Raid + LILO HOWTO

Available in LaTeX (for DVI and PostScript), plain text, and HTML.

> http://www.linuxdoc.org/HOWTO/Boot+Root+Raid+LILO.html

Available in SGML and HTML.

> ftp.bizsystems.net/pub/raid/

## 2.3 Documentation -- Recommended Reading

If you plan on using raid1/5 over raid0, please read:

> /usr/src/linux/Documentation/initrd.txt

as well as the documentation and man pages that accompany the raidtools set.

and..... Software-RAID-HOWTO.html

## 2.4 RAID resources

Mailing lists can be joined at:

- This one seems quiet: majordomo@nuclecu.unam.mx send a message to subscribe raiddev

  send mail to: raiddev@nuclecu.unam.mx

- Raid development: majordomo@vger.rutgers.edu send a message to subscribe linux-raid

  send mail to: linux-raid@vger.rutgers.edu (this seems to be the most active list)

## 3. Bootable Raid

I'm not going to cover the fundamentals of setting up raid0/1/5 on Linux, that is covered in detail elsewhere. The problem I will address is setting up raid on root and making it bootable with standard LILO. The documentation that comes with the LILO sources (not the man pages) and with the raidtools-0.90, covers the details of booting and boot parameters as well as general raid setup - respectively.

There are two scenarios which are covered here. Set up of bootable root raid and the conversion of an existing non-raid system to bootable root raid without data loss.

## 3.1 Booting RAID 1 with standard LILO

To make the boot information redundant and easy to maintain, set up a small RAID1 and mount it on the /boot directory of your system disk. LILO does not know about device 0x9?? and can not find the information at boot time because the raid sub system is not active then. As a simple work around, you can pass LILO the geometry information of the drive(s) and from that, LILO can determine the position of the information needed to load the kernel even though it is on the RAID1 partition. This is because the RAID1 partition is the same as a standard partition but with a raid super-block written at the end. The boot raid set should fall with the first 1024 mbytes of the disk drive. In theory the start of the raid partition could fall anywhere in the 1024 megs, but in practice I was unable to get it to work unless the boot-raid started at the first block of the set. This is probably because of something dumb that I did, but it was not worth following up at the time. Since then I've simply set up all my systems with the boot-raid set as the first partition. I have root raid system configurations with bootable RAID1 mounted on /boot with root raid sets as follows: RAID1, RAID5, RAID10 & RAID1-10 ( 1 mirror + 1 raid0 set). The last has a very peculiar lilo file pair since none of the disk geometries are the same, however, the principals are the same for the initial boot process. The RAID10 and RAID1-10 root mounts require the use of initrd to mount root after the boot process has taken place. See the appendices for the configuration files for all of these example systems.

A conventional LILO config file stripped down looks like this:

    # lilo.conf - assumes drive less than 1024
            boot = /dev/hda
            delay = 40               # extra, but nice
            vga = normal             # not normally needed
            image = /bzImage
            root = /dev/hda1
            read-only
            label = Linux

A raid LILO config file pair would look like this:

    # lilo.conf.hda - primary ide master
            disk=/dev/md0
            bios=0x80
            sectors=63
            heads=16
            cylinders=39770
            partition=/dev/md1
            start=63
            boot=/dev/hda
            map=/boot/map
            install=/boot/boot.b
            image=/boot/bzImage
            root=/dev/md0
            read-only
            label=LinuxRaid

    # ---------------------

    # lilo.conf.hdc - secondary ide master
            disk=/dev/md0
            bios=0x80                # see note below
            sectors=63
            heads=16
            cylinders=39770
            partition=/dev/md1
            start=63
            boot=/dev/hdc            # this is the other disk
            map=/boot/map
            install=/boot/boot.b
            image=/boot/bzImage
            root=/dev/md0
            read-only
            label=LinuxRaid

# BIOS=line -- if your bios is smart enough (most are not) to detect that that the first disk is missing or failed and will automatically boot from the second disk, then bios=81 would be the appropriate entry here. This is more common with SCSI bios than IDE bios. I simply plan on relocating the drive so it will replace the dead drive C: in the event of failure of the primary boot drive.

The geometry information for the drive can be obtained from fdisk with the command:

    fdisk -ul (little L)
    fdisk -ul /dev/hda

    Disk /dev/hda: 16 heads, 63 sectors, 39770 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hda1            63     33263     16600+  fd  Linux raid autodetect
    /dev/hda2         33264    443519    205128   82  Linux swap
    /dev/hda3        443520  40088159  19822320   fd  Linux raid autodetect

    * note the listing of the START of each partition

## 3.2 Detailed explaination of lilo.conf for raid boot

The raid lilo.conf file above, commented in detail for each entry.

    # lilo.conf.hda - primary ide master
    #       the location of the /boot directory that will be
    #       designated below as containing the kernel, map, etc...
    #       note that this is NOT the actual partition containing
    #       the boot image and info, but rather the device
    #       that logically contains this directory.
    #       in this example, /dev/md1 is mounted on /dev/md0/boot
         disk=/dev/md0

    #       tell LILO which bios device to use for boot, i.e. C: drive
         bios=0x80

    #       tell LILO the geometry of the device
    #       this is usually but not always the "logical"
    #       geometry. Check the /proc file system or watch
    #       the boot messages when the kernel probes for the drive
    #
         sectors=63
         heads=16
         cylinders=39770

    #       this is a dummy entry to make LILO happy so it
    #       will recognize the raid set 0x9?? and then find
    #       the START of the boot sector. To really see
    #       what this was for, read the documentation
    #       that comes with the LILO source distribution.
    #       This parameter "must" be different than the
    #       disk=  entry above. It can be any other mdx
    #       device, used or unused and need not be the one
    #       that contains the /boot information
    #
         partition=/dev/md1

    #       the first sector of the partition containing /boot information
         start=63

    #       the real device that LILO will write the boot information to
         boot=/dev/hda

    #       logically where LILO will put the boot information
         map=/boot/map
         install=/boot/boot.b

    #       logically where lilo will find the kernel image
         image=/boot/bzImage

    #       standard stuff after this
    #       root may be a raid1/4/5 device
         root=/dev/md0
         read-only
         label=LinuxRaid

## 4. Upgrading from non-raid to RAID1/4/5

Upgrading a non-raid system to raid is fairly easy and consists of several discrete steps described below. The description is for a system with a boot partition, root partition and swap partition.

    OLD disk in the existing system:

        /dev/hda1     boot, may be dos+lodlin or lilo
        /dev/hda2     root
        /dev/hda3     swap

We will add an additional disk and convert the entire system to RAID1. You could easily add several disks and make a RAID5 set instead using the same procedure.

## 4.1 Step 1 - prepare a new kernel

Download a clean kernel, raidtools-0.90 (or the most recent version), and the kernel patch to upgrade the kernel to 0.90 raid.

Compile and install the raidtools and READ the documentation.

Compile and install the kernel to support all the flavors (0/1/4/5 ?) of raid that you will be using. Make sure to specify autostart of raid devices in the kernel configuration. Test that the kernel boots properly and examine /proc/mdstat to see that the raid flavors you will use are supported by the new kernel.

## 4.2 Step 2 - set up raidtab for your new raid.

The new disk will be added to an additional IDE controller as the master device, thus becomming /dev/hdc

        /dev/hdc1     16megs -- more than enough for several kernel images
        /dev/hdc2     most of the disk
        /dev/hdc3     some more swap space, if needed. otherwise add to hdc2

Change the partition types for /dev/hdc1 and /dev/hdc2 to "fd" for raid-autostart.

Using the failed-disk parameter, create a raidtab for the desired RAID1 configuration. The failed disk must be the last entry in the table.

    # example raidtab
    # md0 is the root array
    raiddev                 /dev/md0
    raid-level              1
    nr-raid-disks           2
    chunk-size              32
    # Spare disks for hot reconstruction
    nr-spare-disks          0
    persistent-superblock   1
    device                  /dev/hdc2
    raid-disk               0
    # this is our old disk, mark as failed for now
    device                  /dev/hda2
    failed-disk             1

    # md1 is the /boot array
    raiddev                 /dev/md1
    raid-level              1
    nr-raid-disks           2
    chunk-size              32
    # Spare disks for hot reconstruction
    nr-spare-disks          0
    persistent-superblock   1
    device                  /dev/hdc1
    raid-disk               0
    # boot is marked failed as well
    device                  /dev/hda1
    failed-disk               1

## 4.3 Create, format, and configure RAID

Create the md devices with the commands:

        mkraid /dev/md0
        mkraid /dev/md1

The raid devices should be created and start. Examination of /proc/mdstat should show the raid personalities in the kernel and the raid devices running.

Format the boot and root devices with:

        mke2fs /dev/md0
        mke2fs /dev/md1

Mount the new root device somewhere handy and create the /boot directory and mount the boot partition.

        mount /dev/md0 /mnt
        mkdir /mnt/boot
        mount /dev/md1 /mnt/boot

## 4.4 Copy the current OS to the new raid device

This is pretty straightforward.

        cd /
        # set up a batch file to do this
        cp -a /bin /mnt
        cp -a /dev /mnt
        cp -a /etc /mnt
        cp -a (all directories except /mnt, /proc, and nsf mounts) /mnt

This operation can be tricky if you have mounted or linked other disks to your root file system. The example above assumes a very simple system, you may have to modify the procedure somewhat.

## 4.5 Test your new RAID

Make a boot floppy and rdev the kernel.

        dd if=kernal.image of=/dev/fd0 bs=2k
        rdev /dev/fd0 /dev/md0
        rdev -r /dev/fd0 0
        rdev -R /dev/fd0 1

Modify the fstab on the RAID device to reflect the new mount points as follows:

      /dev/md0        /       ext2    defaults        1 1
      /dev/md1        /boot   ext2    defaults        1 1

Dismount the raid devices and boot the new file system to see that all works correctly.

        umount /mnt/boot
        umount /mnt
        raidstop /dev/md0
        raidstop /dev/md1
        shutdown -r now

Your RAID system should now be up and running in degraded mode with a floppy boot disk. Carefully check that you transferred everything to the new raid system. If you mess up here without a backup, YOU ARE DEAD!

If something did not work, reboot your old system and go back and fix things up until you successfully complete this step.

## 4.6 Integrate old disk into raid array

Success in the previous step means that the raid array is now operational, but without redundancy. We must now re-partition the old drive(s) to fit into the new raid array. Remember that if the geometries are not the same, the the partition size on the old drive must be the same or larger than the raid partitions or they can not be added to the raid set.

Re-partition the old drive as required. Example:

        /dev/hda1     same or larger than /dev/hdc1
        /dev/hda2     same or larger than /dev/hdc2
        /dev/hda3     anything left over for swap or whatever...

Change the failed-disk parameter in the raidtab to raid-disk and hot add the new (old) disk partitions to the raid array.

        raidhotadd /dev/md1 /dev/hda1
        raidhotadd /dev/md0 /dev/hda2

Examining /proc/mdstat should show one or more of the raid devices reconstructing the data for the new partitions. After a minute or two... or so, the raid arrays should be fully synchronized (this could take a while for a large partition).

Using the procedure described in the first sections of this document, set up bootable raid on the new raid pair. Hang on to that boot floppy while setting up and testing this last step.

## 5. Appendix A. - example raidtab

RAID1 example described in the first sections of this document

     df
    Filesystem           1k-blocks      Used Available Use% Mounted on
    /dev/md0              19510780   1763188  16756484  10% /
    /dev/md1                 15860       984     14051   7% /boot

    # --------------------------

     fdisk -ul /dev/hda

    Disk /dev/hda: 16 heads, 63 sectors, 39770 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hda1            63     33263     16600+  fd  Linux raid autodetect
    /dev/hda2         33264    443519    205128   83  Linux native
    /dev/hda3        443520  40088159  19822320   fd  Linux raid autodetect

    # --------------------------

     fdisk -ul /dev/hdc

    Disk /dev/hdc: 16 heads, 63 sectors, 39770 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hdc1            63     33263     16600+  fd  Linux raid autodetect
    /dev/hdc2         33264    443519    205128   82  Linux swap
    /dev/hdc3        443520  40088159  19822320   fd  Linux raid autodetect

    # --------------------------

    # md0 is the root array, about 20 gigs
    raiddev                 /dev/md0
    raid-level              1
    nr-raid-disks           2
    chunk-size              32
    # Spare disks for hot reconstruction
    nr-spare-disks          0
    persistent-superblock   1
    device                  /dev/hda3
    raid-disk               0
    device                  /dev/hdc3
    raid-disk               1

    # md1 is the /boot array, about 16 megs
    raiddev                 /dev/md1
    raid-level              1
    nr-raid-disks           2
    chunk-size              32
    # Spare disks for hot reconstruction
    nr-spare-disks          0
    persistent-superblock   1
    device                  /dev/hda1
    raid-disk               0
    device                  /dev/hdc1
    raid-disk               1

    # --------------------------

    # GLOBAL SECTION
    # device containing /boot directory
    disk=/dev/md0
    # geometry
      bios=0x80
      sectors=63
      heads=16
      cylinders=39770
    # dummy
      partition=/dev/md1
    # start of device "disk" above
      start=63

    boot=/dev/hda
    map=/boot/map
    install=/boot/boot.b

    image=/boot/bzImage
    root=/dev/md0
    label=LinuxRaid
    read-only

    # -------------------------

    # GLOBAL SECTION
    # device containing /boot directory
    disk=/dev/md0
    # geometry
      bios=0x80
      sectors=63
      heads=16
      cylinders=39770
    # dummy
      partition=/dev/md1
    # start of device "disk" above
      start=63

    boot=/dev/hdc
    map=/boot/map
    install=/boot/boot.b

    image=/boot/bzImage
    root=/dev/md0
    label=LinuxRaid
    read-only

## 6. Appendix B. - SCSI reference implementation RAID5

4 disk SCSI RAID5

     df
    Filesystem           1k-blocks      Used Available Use% Mounted on
    /dev/md0              11753770   2146076   9000678  19% /
    /dev/md1                 15739       885     14042   6% /boot

    # --------------------------

     fdisk -ul /dev/sda

    Disk /dev/sda: 64 heads, 32 sectors, 4095 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/sda1            32     32767     16368   fd  Linux raid autodetect
    /dev/sda2         32768    292863    130048    5  Extended
    /dev/sda3        292864   8386559   4046848   fd  Linux raid autodetect
    /dev/sda5         32800    260095    113648   82  Linux swap
    /dev/sda6        260128    292863     16368   83  Linux native - test

    # ------------------------

     fdisk -ul /dev/sdb

    Disk /dev/sdb: 64 heads, 32 sectors, 4095 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/sdb1            32     32767     16368   fd  Linux raid autodetect
    /dev/sdb2         32768    292863    130048    5  Extended
    /dev/sdb3        292864   8386559   4046848   fd  Linux raid autodetect
    /dev/sdb5         32800    260095    113648   82  Linux swap
    /dev/sdb6        260128    292863     16368   83  Linux native - test

    # ------------------------

    # fdisk -ul /dev/sdc

    Disk /dev/sdc: 64 heads, 32 sectors, 4095 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/sdc2            32    292863    146416    5  Extended
    /dev/sdc3        292864   8386559   4046848   fd  Linux raid autodetect
    /dev/sdc5            64    260095    130016   83  Linux native - development
    /dev/sdc6        260128    292863     16368   83  Linux native - test

    # ------------------------

     fdisk -ul /dev/sdd

    Disk /dev/sdd: 64 heads, 32 sectors, 4095 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/sdd2            32    292863    146416    5  Extended
    /dev/sdd3        292864   8386559   4046848   fd  Linux raid autodetect
    /dev/sdd5            64    260095    130016   83  Linux native - development
    /dev/sdd6        260128    292863     16368   83  Linux native - test

    # --------------------------

    # raidtab
    #
    raiddev /dev/md0
            raid-level      5
            nr-raid-disks   4
            persistent-superblock 1
            chunk-size      32

    # Spare disks for hot reconstruction
            nr-spare-disks  0
            device          /dev/sda3
            raid-disk       0
            device          /dev/sdb3
            raid-disk       1
            device          /dev/sdc3
            raid-disk       2
            device          /dev/sdd3
            raid-disk       3

    # boot partition
    #
    raiddev /dev/md1
            raid-level      1
            nr-raid-disks   2
            persistent-superblock 1
            chunk-size      32

    # Spare disks for hot reconstruction
            nr-spare-disks  0
            device          /dev/sda1
            raid-disk       0
            device          /dev/sdb1
            raid-disk       1

    # --------------------------

    # cat lilo.conf.sda
    # GLOBAL SECTION
    # device containing /boot directory
    disk=/dev/md0
    # geometry
      bios=0x80
      sectors=32
      heads=64
      cylinders=4095
    # dummy
      partition=/dev/md1
    # start of device "disk" above
      start=32

    boot=/dev/sda
    map=/boot/map
    install=/boot/boot.b

    image=/boot/bzImage
    root=/dev/md0
    label=LinuxRaid
    read-only

    # ------------------------
    # cat lilo.conf.sdb
    # GLOBAL SECTION
    # device containing /boot directory
    disk=/dev/md0
    # geometry
      bios=0x80
      sectors=32
      heads=64
      cylinders=4095
    # dummy
      partition=/dev/md1
    # start of device "disk" above
      start=32

    boot=/dev/sdb
    map=/boot/map
    install=/boot/boot.b

    image=/boot/bzImage
    root=/dev/md0
    label=LinuxRaid
    read-only

## 7. Appendix C. - ide RAID10 with initrd

RAID1 over striped RAID0 pair.... the disks in the RAID0 sets are not quite the same size, but close enough.

    /dev/md0 is the /boot partition and is autostarted by the kernel
    /dev/md1 and /dev/md3 are the two RAID0 sets autostarted by the kernel
    /dev/md2 is the root partition and is started by initrd

    df
    Filesystem           1k-blocks      Used Available Use% Mounted on
    /dev/md2                118531     76485     35925  68% /
    /dev/md0                  1917      1361       457  75% /boot

    # ----------------------------

     fdisk -ul /dev/hda

    Disk /dev/hda: 4 heads, 46 sectors, 903 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hda1            46      4231      2093   fd  Linux raid autodetect
    /dev/hda2          4232    166151     80960   fd  Linux raid autodetect

    # ----------------------------

     fdisk -ul /dev/hdb

    Disk /dev/hdb: 5 heads, 17 sectors, 981 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hdb1            17     83384     41684   fd  Linux raid autodetect

    # ----------------------------

     fdisk -ul /dev/hdc

    Disk /dev/hdc: 7 heads, 17 sectors, 1024 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hdc1            17     84013     41998+  fd  Linux raid autodetect
    /dev/hdc2         84014    121855     18921   82  Linux swap

    # ----------------------------

     fdisk -ul /dev/hdd

    Disk /dev/hdd: 4 heads, 46 sectors, 903 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hdd1            46      4231      2093   fd  Linux raid autodetect
    /dev/hdd2          4232    166151     80960   fd  Linux raid autodetect

    # ----------------------------

    # raidtab
    #
    raiddev /dev/md0
            raid-level      1
            nr-raid-disks   2
            persistent-superblock   1
            chunk-size      8
            device          /dev/hda1
            raid-disk       0
            device          /dev/hdd1
            raid-disk       1

    raiddev /dev/md1
            raid-level      0
            nr-raid-disks   2
            persistent-superblock   1
            chunk-size      8
            device          /dev/hdd2
            raid-disk       0
            device          /dev/hdb1
            raid-disk       1

    raiddev /dev/md2
            raid-level      1
            nr-raid-disks   2
            persistent-superblock   1
            chunk-size      8
            device          /dev/md1
            raid-disk       0
            device          /dev/md3
            raid-disk       1

    raiddev /dev/md3
            raid-level      0
            nr-raid-disks   2
            persistent-superblock   1
            chunk-size      8
            device          /dev/hda2
            raid-disk       0
            device          /dev/hdc1
            raid-disk       1

    # ----------------------------

    contents of linuxrc

     cat linuxrc
    #!/bin/sh
    # ver 1.02 2-22-00
    #
    ############# really BEGIN 'linuxrc' ###############
    #
    # mount the proc file system
    /bin/mount /proc

    # start raid 1 made of raid 0's
    /bin/raidstart /dev/md2

    # tell the console what's happening
    /bin/cat /proc/mdstat

    # Everything is fine, let the kernel mount /dev/md2
    # tell the kernel to switch to /dev/md2 as the /root device
    # The 0x900 value is the device number calculated by:
    #  256*major_device_number + minor_device number
    echo "/dev/md2 mounted on root"
    echo 0x902>/proc/sys/kernel/real-root-dev

    # umount /proc to deallocate initrd device ram space
    /bin/umount /proc
    exit

    # ----------------------------

    contents of initrd

    ./bin/ash
    ./bin/echo
    ./bin/raidstart
    ./bin/mount
    ./bin/umount
    ./bin/cat
    ./bin/sh
    ./dev/tty1
    ./dev/md0
    ./dev/md1
    ./dev/md2
    ./dev/md3
    ./dev/md4
    ./dev/console
    ./dev/hda
    ./dev/hda1
    ./dev/hda2
    ./dev/hda3
    ./dev/hdb
    ./dev/hdb1
    ./dev/hdb2
    ./dev/hdb3
    ./dev/hdc
    ./dev/hdc1
    ./dev/hdc2
    ./dev/hdc3
    ./dev/hdd
    ./dev/hdd1
    ./dev/hdd2
    ./dev/hdd3
    ./dev/initrd
    ./dev/ram0
    ./dev/ram1
    ./dev/ram2
    ./dev/ram3
    ./dev/ram4
    ./dev/ram5
    ./dev/ram6
    ./dev/ram7
    ./etc/raidtab
    ./etc/fstab
    ./lib/ld-2.1.2.so
    ./lib/ld-linux.so.1
    ./lib/ld-linux.so.1.9.9
    ./lib/ld-linux.so.2
    ./lib/ld.so
    ./lib/libc-2.1.2.so
    ./lib/libc.so.6
    ./linuxrc
    ./proc

## 8. Appendix D. - ide RAID1-10 with initrd

This is a system made up of an assortment of odds and ends. The root mounted raid device is comprised of a RAID1 made up of one RAID0 array from odd sized disks and a larger regular disk partition. Examination of the lilo.conf files may give you better insight into the reasoning behind the various parameters.

    /dev/md0 is the /boot partition and is autostarted by the kernel
    /dev/md1 is one half of the mirror set for md2, autostarted by kernel
    /dev/hda3 is the other half of the mirror set for md2
    /dev/md2 is the RAID1 /dev/md1 + /dev/hda3, started by initrd

    df
    Filesystem           1k-blocks      Used Available Use% Mounted on
    /dev/md2                138381     74421     56815  57% /
    /dev/md0                  2011      1360       549  71% /boot

    # ----------------------------

     fdisk -ul /dev/hda

    Disk /dev/hda: 8 heads, 46 sectors, 903 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hda1            46      4415      2185   fd  Linux raid autodetect
    /dev/hda2          4416     43423     19504   82  Linux swap
    /dev/hda3         43424    332303    144440   83  Linux native

    # ----------------------------

     fdisk -ul /dev/hdc

    Disk /dev/hdc: 8 heads, 39 sectors, 762 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hdc1            39      4367      2164+  fd  Linux raid autodetect
    /dev/hdc2          4368     70199     32916   82  Linux swap
    /dev/hdc3         70200    237743     83772   fd  Linux raid autodetect

    # ----------------------------

     fdisk -ul /dev/hdd

    Disk /dev/hdd: 4 heads, 39 sectors, 762 cylinders
    Units = sectors of 1 * 512 bytes

       Device Boot    Start       End    Blocks   Id  System
    /dev/hdd1            39    118871     59416+  fd  Linux raid autodetect

    # ----------------------------

    # raidtab
    #
    raiddev /dev/md0
            raid-level      1
            nr-raid-disks   2
            persistent-superblock   1
            chunk-size      8
            device          /dev/hdc1
            raid-disk       1
            device          /dev/hda1
            raid-disk       0

    raiddev /dev/md1
            raid-level      0
            nr-raid-disks   2
            persistent-superblock   1
            chunk-size      8
            device          /dev/hdc3
            raid-disk       0
            device          /dev/hdd1
            raid-disk       1

    raiddev /dev/md2
            raid-level      1
            nr-raid-disks   2
            persistent-superblock   1
            chunk-size      8
            device          /dev/md1
            raid-disk       1
            device          /dev/hda3
            raid-disk       0

    # ----------------------------

     cat linuxrc
    #!/bin/sh
    # ver 1.02 2-22-00
    #
    ############# really BEGIN 'linuxrc' ###############
    #
    # mount the proc file system
    /bin/mount /proc

    # autostart /boot partition and raid0
    /bin/raidstart /dev/md2

    # tell the console what's happening
    /bin/cat /proc/mdstat

    # Everything is fine, let the kernel mount /dev/md2
    # tell the kernel to switch to /dev/md2 as the /root device
    # The 0x900 value is the device number calculated by:
    #  256*major_device_number + minor_device number
    echo "/dev/md2 mounted on root"
    echo 0x902>/proc/sys/kernel/real-root-dev

    # umount /proc to deallocate initrd device ram space
    /bin/umount /proc
    exit

    # ----------------------------

    contents of initrd.gz

    ./bin
    ./bin/ash
    ./bin/echo
    ./bin/raidstart
    ./bin/mount
    ./bin/umount
    ./bin/cat
    ./bin/sh
    ./dev/tty1
    ./dev/md0
    ./dev/md1
    ./dev/md2
    ./dev/md3
    ./dev/console
    ./dev/hda
    ./dev/hda1
    ./dev/hda2
    ./dev/hda3
    ./dev/hdc
    ./dev/hdc1
    ./dev/hdc2
    ./dev/hdc3
    ./dev/hdd
    ./dev/hdd1
    ./dev/hdd2
    ./dev/hdd3
    ./dev/initrd
    ./dev/ram0
    ./dev/ram1
    ./dev/ram2
    ./dev/ram3
    ./dev/ram4
    ./dev/ram5
    ./dev/ram6
    ./dev/ram7
    ./etc/raidtab
    ./etc/fstab
    ./lib/ld-2.1.2.so
    ./lib/ld-linux.so.1
    ./lib/ld-linux.so.1.9.9
    ./lib/ld-linux.so.2
    ./lib/ld.so
    ./lib/libc-2.1.2.so
    ./lib/libc.so.6
    ./linuxrc
    ./proc

    # ----------------------------

     cat lilo.conf.hda
    # GLOBAL SECTION
    # device containing /boot directory
    disk=/dev/md2
    # geometry
      bios=0x80
      cylinders=903
      heads=8
      sectors=46
    # geometry for 2nd disk
    # bios will be the same because it will have to be moved to hda
    #  cylinders=762
    #  heads=8
    #  sectors=39

    # dummy
      partition=/dev/md0
    # start of device "disk" above
      start=46
    # second device
    #  start=39

    # seem to have some trouble with 2.2.14 recognizing the right IRQ
      append = "ide1=0x170,0x376,12 ether=10,0x300,eth0 ether=5,0x320,eth1"

    boot=/dev/hda
    map=/boot/map
    install=/boot/boot.b

    initrd=/boot/initrd.gz

    image=/boot/zImage
    root=/dev/md2
    label=LinuxRaid
    read-only

    # ----------------------------

     cat lilo.conf.hdc
    # GLOBAL SECTION
    # device containing /boot directory
    disk=/dev/md2
    # geometry
      bios=0x80
    #  cylinders=903
    #  heads=8
    #  sectors=46
    # geometry for 2nd disk
    # bios will be the same because it will have to be moved to hda
      cylinders=762
      heads=8
      sectors=39

    # dummy
      partition=/dev/md0
    # start of device "disk" above
    #  start=46
    # second device
      start=39

    # seem to have some trouble with 2.2.14 recognizing the right IRQ
      append = "ide1=0x170,0x376,12 ether=10,0x300,eth0 ether=5,0x320,eth1"

    boot=/dev/hdc
    map=/boot/map
    install=/boot/boot.b

    initrd=/boot/initrd.gz

    image=/boot/zImage
    root=/dev/md2
    label=LinuxRaid
    read-only