Debian Software RAID-1 (without recompiling) Mini Howto

Some notes to explain how to make a software raid-1 (mirror) in Debian *without* linux kernel recompiling.
We will use a standard debian distribution kernel and a Gentoo live cd to make the raid.
Debian release: sarge net install (testing).
Linux kernel version: 2.4.22

1. Install a minimal GNU/Linux Debian system

   (e.g. http://www.debian.org/CD/netinst)
   
   Fig. 1
   
   
   
   Fig. 2
   
   

2. Install raidtools2 debian package

   Choose to start RAID array automatically on startup beacause we will use the md driver as a module.
   
   Fig. 3
   
   

3. Booting Gentoo Live CD...

   http://www.gentoo.org
   
   Fig. 4
   
   

4. Create md devices

   cdimage root # mknod /dev/md0 b 9 0 cdimage root # mknod /dev/md1 b 9 1 cdimage root # mknod /dev/md2 b 9 2

5. Create /etc/raidtab

   raiddev /dev/md0 raid-level 1 nr-raid-disks 2 nr-spare-disks 0 chunk-size 16 persistent-superblock 1 device /dev/sda1 raid-disk 0 device /dev/sdb1 raid-disk 1 raiddev /dev/md1 raid-level 1 nr-raid-disks 2 nr-spare-disks 0 chunk-size 16 persistent-superblock 1 device /dev/sda3 raid-disk 0 device /dev/sdb3 raid-disk 1 raiddev /dev/md2 raid-level 1 nr-raid-disks 2 nr-spare-disks 0 chunk-size 16 persistent-superblock 1 device /dev/sda4 raid-disk 0 device /dev/sdb4 raid-disk 1

6. Start RAID devices

   cdimage root # mkdraid --really-force /dev/md0 cdimage root # mkdraid --really-force /dev/md1 cdimage root # mkdraid --really-force /dev/md2

   
   You can check the completion progress by cat'ing the /proc/mdstat file
   
   

   cdimage root # watch cat /proc/mdstat

7. Mount, copy raidtab and chroot debian root

   cdimage root # cdimage root # mkdir -p /mnt/debian cdimage root # mount -t ext3 /dev/md0 /mnt/debian cdimage root # cp /etc/raidtab /mnt/debian/etc cdimage root # chroot /mnt/debian cdimage:/# mount -t ext3 /dev/sda1 /boot cdimage:/# mount -t ext3 /dev/sda4 /var cdimage:/# mount -t proc proc /proc

8. Edit /etc/fstab

   # /etc/fstab: static file system information. # # /dev/md1 / ext3 defaults,errors=remount-ro 0 1 /dev/md0 /boot ext3 defaults 0 2 /dev/md2 /var ext3 defaults 0 2 /dev/sda2 none swap sw 0 0 /dev/fd0 /floppy auto rw,user,noauto 0 0 /dev/hda /cdrom auto ro,user,noauto 0 0 proc /proc proc defaults 0 0

9. Set root partition via mkinitrd

   cdimage:/# mkinitrd -r /dev/md1 -o /boot/initrd.img-2.4.22-1-386 /lib/modules/2.4.22-1-386/

10. Edit /etc/lilo.conf and run lilo

    boot=/dev/md0 root=/dev/md1 raid-extra-boot=mbr-only install=/boot/boot.b map=/boot/map image=/vmlinuz   label=Linux   initrd=/initrd.img

11. Unmount, exit chroot and unmount

    cdimage:/# unmount /boot cdimage:/# unmount /var cdimage:/# unmount /proc cdimage root # unmount /mnt/debian

12. Check and resize filesystems

    cdimage:/# e2fsck -f /dev/md0 cdimage:/# e2fsck -f /dev/md1 cdimage:/# e2fsck -f /dev/md2 cdimage:/# resize2fs /dev/md0 cdimage:/# resize2fs /dev/md1 cdimage:/# resize2fs /dev/md2

    
    This will generate an error about inconsistent sizes and possibly corrupted superblock. Say N to 'Abort?'.
    

13. Stop RAID and reboot

    cdimage:/# raidstop /dev/md0 cdimage:/# raidstop /dev/md1 cdimage:/# raidstop /dev/md2 cdimage:/# reboot

14. Debian RAID-1 up and running

    
    Fig. 5
    
    

15. Caveats

    You may encounter filesystem errors in /dev/md0, /dev/md2 at first boots.
    I have had to do:
    
    

    debian:~# raidstop /dev/md0 debian:~# raidstop /dev/md2 debian:~# mkraid -R /dev/md0 debian:~# mkraid -R /dev/md2 debian:~# mount -t ext3 /dev/md0 /boot debian:~# mount -t ext3 /dev/md2 /var

16. GNU Free Documentation

    Please, see fdl.txt