-We 're going to mirror /, /boot and /var.
/home will be backed up with a cronjob in a tar.gz file every day to its counterpart partition on the other disk. Since we have a big disk, this will allow us to have at least 2 different backups as long as the disks aren 't half filled. This contains only user data, no system files are on this disk.
The safest way to mirror is to setup a broken mirror and first copy the data to it, boot from it and add the original disk to the mirror, overwriting its data with its own copy. Still with me? Ok, pratically this means copying /, /boot and /var to the other disk, sdb, mounted somewhere as a half mirror. Do this in runlevel 1 so no data changes meanwhile. Next boot from it, sfdisk /dev/sdb to /dev/sda and add the raid partitions from sda to the mirrors. This will copy back the data from sdb paritions to the sda partitions. More on that later on.
3. Get on with mdadm
-Zero out any superblock still existing from previous mirror attempts
mdadm --zero-superblock /dev/sdb1 mdadm --zero-superblock /dev/sdb6 mdadm --zero-superblock /dev/sdb7
-Copy partition information from sda to sdb using sfdisk
sfdisk -d /dev/sda > sda.out
Dump layout of sda to a file edit file with vi and replace sda entries by sdb
sfdisk /dev/sdb < sda.out
-Change partition types of partitions to mirror with fdisk. This is very important, otherwise Linux won 't boot from it!
fdisk /dev/sdb
"t" for toggle partition type
change raidable partitions (check your fstab) to "fd" = Linux Raid Autodetect
"w" to write and quit fdisk
-Set up a broken mirror on /dev/sdb partitions
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 missing
mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sdb6 missing
mdadm --create /dev/md2 --level=1 --raid-devices=2 /dev/sdb7 missing
This will start the raid devices. Dump this information to mdadm.conf for later use
mdadm -Esb /dev/sdb1 >> /etc/mdadm.conf
mdadm -Esb /dev/sdb6 >> /etc/mdadm.conf
mdadm -Esb /dev/sdb7 >> /etc/mdadm.conf
I like editing this file manually afterwards.
=> remove the lines where it says "devices="... and add a line above ARRAY that says
"DEVICE /dev/sda1 /dev/sdb1 /sdev/sda6 /dev/sdb6 /dev/sda7 /dev/sdb7"
This will make your kernel complain about missing devices when you restart from your broken mirror, but this way this file is already what it should be
-Next, create filesystems on it. I 'm gonna take the opportunity to make them ext3 instead of the original ext2
mkfs.ext3 /dev/md0
mkfs.ext3 /dev/md1
mkfs.ext3 /dev/md2
4. Offline operations
-Better than switching to runlevel 1, boot from a bootable Linux CD that supports raid and your harddisk controller.
Trinity Rescue Kit has the necessary tools to do so.
Why? Because filesystems like /dev will not be mounted over your existing /dev, which contains the static /dev special file entries in case udev doesn 't work.
Make dirs to mount your stuff on
mkdir /sda1
mkdir /sda6
mkdir /sda7
mkdir /md0
mkdir /md1
mkdir /md2
-Mount /dev/sda partitions in read-only and copy mdadm.conf from /sda6/etc/mdadm.conf to your current /etc from your bootcd
mount -o ro /dev/sda1 /sda1
mount -o ro /dev/sda1 /sda6
mount -o ro /dev/sda1 /sda7
cp -f /sda6/etc/mdadm.conf /etc
-Start your RAID devices
mdadm -As
-Mount your RAID devices
mount /dev/md0 /md0
mount /dev/md0 /md1
mount /dev/md0 /md2
-Copy all your data
cp -a /sda1/* /md0
cp -a /sda6/* /md1
cp -a /sda7/* /md2
You can check the progress of this copy in another console with "df"
-Once the data is copied, we 're gonna modify the fstab, next lilo
The fstab on /md1/etc/ should become something like this:
/dev/md1 / ext3 defaults 1 1
/dev/md0 /boot ext3 defaults 1 2
none /dev/pts devpts mode=0620 0 0
/dev/sda8 /home ext2 defaults 1 2
/dev/hdb /mnt/cdrom auto umask=0,user,codepage=850,iocharset=iso8859-1,noauto,ro
,exec 0 0
none /mnt/floppy supermount dev=/dev/fd0,fs=ext2:vfat,--,umask=0,iocharset=utf8,
sync 0 0
none /proc proc defaults 0 0
/dev/md2 /var ext3 defaults 1 2
/dev/sda5 swap swap defaults 0 0
/dev/sdb5 swap swap defaults 0 0
5. Lilo
The easiest way for lilo not to complain is to chroot to the mounted raid root, but first submount its /boot partition to it
umount /md0
mount /dev/md0 /md1/boot
-System Rescue CD specific: copy zsh to your soon to be chrooted /bin
cp /bin/zsh /md1/bin
-Chroot, run bash and edit lilo.conf
chroot /md1
bash
vi /etc/lilo.conf
-Here 's what the original lilo.conf looks like:
# File generated by DrakX/drakboot
# WARNING: do not forget to run lilo after modifying this file
default="linux"
boot=/dev/sda
map=/boot/map
keytable=/boot/be2-latin1.klt
prompt
nowarn
timeout=100
message=/boot/message
menu-scheme=wb:bw:wb:bw
image=/boot/vmlinuz
label="linux"
root=/dev/sda1
initrd=/boot/initrd.img
append="resume=/dev/sda5 splash=silent"
vga=788
read-only
image=/boot/vmlinuz
label="linux-nonfb"
root=/dev/sda1
initrd=/boot/initrd.img
append="resume=/dev/sda5"
read-only
image=/boot/vmlinuz
label="failsafe"
root=/dev/sda1
initrd=/boot/initrd.img
append="failsafe resume=/dev/sda5 devfs=nomount"
read-only
-Here 's the new one:
default="linux-md"
boot=/dev/md0
raid-extra-boot=mbr
map=/boot/map
keytable=/boot/be2-latin1.klt
prompt
nowarn
timeout=100
message=/boot/message
menu-scheme=wb:bw:wb:bw
image=/boot/vmlinuz-2.6.11custom
label="linux-md"
root=/dev/md1
vga=1
read-only
image=/boot/vmlinuz
label="linux-nonfb"
root=/dev/sda1
initrd=/boot/initrd.img
append="resume=/dev/sda5"
read-only
image=/boot/vmlinuz
label="failsafe"
root=/dev/sda1
initrd=/boot/initrd.img
append="failsafe resume=/dev/sda5 devfs=nomount"
read-only
My newly compiled kernel is called /boot/vmlinuz-2.6.11custom, my boot device is /dev/md0.
See to it that the underlying partitions have their "active" bit set (in fdisk, "a", sdb1)
The line "raid-extra-boot=mbr" will write the bootsector to the currently active raid disks, which will be /dev/sdb.
Now run lilo
If your system is unable to boot from a secondary drive from BIOS, copy lilo.conf to lilo.conf.md, remodify lilo.conf, comment out the "raid-extra-boot=mbr" and change boot back to "boot=/dev/sda"
Run lilo again.
This will write the same boot information to the bootsector of /dev/sda.
You will only need this once, just to be able to start from the "linux-md"
I left an old entry in case the new kernel won 't boot from the mirror.
I 've also thrown out framebuffer support. It 's a personal preference, I don 't like graphics on a server.
"vga=1" will give me a 80x50 screen (you 'll need to remove the SYSFONT entries from /etc/rc.sysinit).
6. Running from a broken mirror and hotadd devices
-Restart and boot "linux-md"
Your system should be running on a broken raid 1.
See that all runs well and your data is all there, processes are running normally.
Check that the output of "mount" gives you md devices
-Once you 've made sure of that, sfdisk your /dev/sdb information to /dev/sda
sfdisk -d /dev/sdb > sdb.out
Dump layout of sdb to a file edit file with vi and replace sdb entries by sda
sfdisk /dev/sda < sdb.out
Check with fdisk that /dev/sda contains exactly the same partitions as /dev/sdb
-Once you 've done all that, you can add your inactive sda partitions to your running raid1 devices, making your system redundant.
mdadm /dev/md0 --add /dev/sda1
mdadm /dev/md1 --add /dev/sda6
mdadm /dev/md2 --add /dev/sda7
Your disks should be synching now. Check the progress in /proc/mdstat
-Copy /etc/lilo.conf.md back to /etc/lilo.conf and run lilo again
Once your disks are synchronised, you should be able to boot from any 2 disks in your system.
-You might need to initiate the second swap on /dev/sdb5
swapon /dev/sdb5
That 's it, you 're running Linux from RAID 1
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