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Installing Debian with SATA based RAID

Now for 2.6 kernel version

I've read that there will soon be an installer that will do raid installs and perhaps even support SATA, but today it is manual. My install on a Intel D865PERL mother board got 'interesting'. The last Debian (beta 4) testing installer does support SATA as does a version of Debian/Libranet, but going on to RAID is a manual task.
The basic idea was to Install all on one drive, then partition the second drive with just the same sizes. Install mdadm (the new and improved replacement for raidtools). I'm assuming we are using clean drives. If one re-uses previously used disks the superblocks must be zeroed (--zero-superblock option to mdadm) before adding the partitions to the array.
This guide was produced using a Tyan S2875 Mother board.
The whole mess is harder than it should be and I hope this page becomes the basis for someone's automating script (hint hint).

Overview of steps

Install Debian on first drive (/dev/sda)
Creating a degraded RAID1 array on disk 2 (/dev/sdb)
Update initrd
Copying the Debian installation over from disk 1 (sda to sdb)
Fix fstab on /dev/md2
Add disk 1 to the degraded array to create final raid array
Update initrd again
Produce /etc/mdadm/mdadm.conf
Setup the monitoring daemon*

In this example Disk1 and disk2 are /dev/sda and /dev/sdb respectively.

The partitions I used are:


/boot 200m
/swap 1Gig raid0
/ rest of drive

It is possible for a system to crash if the swap area drive fails. If this is not a concern you could also set it up as simple swap areas or as raid0 to improve performance. (Raid1 also provides faster reads as a side benefit, but there is the cost slower writes - but swap tends to be read more times than written so you might still come out ahead.)).

Install Debian on first drive

I used the following partitions

Device	Size	Id	Eventual mount point
/dev/sda1	200M	83	/boot/
/dev/sda5	1G	82	swap
/dev/sda6	100G	83	/

I'm assuming you know how to do the above by running fdisk from the install of your choice.

After installing:

#apt-get install wajig

(you don't want to be without wajig - it makes apt and dpkg user friendly)

#wajig install mdadm
#wajig install rsync
#wajig install e3
Update kernel to kernel-image-2.6.8-1-k7-smp

Partition Drive2 with fdisk

Device	Size	Id	Eventual mount point
/dev/sdb1	200M	fd	/boot/
/dev/sdb5	1G	fd	swap
/dev/sdb6	100G	fd	/

Create the raid devices

# mdadm --create /dev/md0 --level 1 --raid-devices=2 missing /dev/sdb1

The above line is the long version of the next line just for reference. .

#mdadm -Cv /dev/md0 -l1 -n2 missing /dev/sdb1
#mdadm -Cv /dev/md1 -l1 -n2 missing /dev/sdb5
#mdadm -Cv /dev/md2 -l1 -n2 missing /dev/sdb6

This creates 3 degraded RAID1 devices (for /boot, swap, and /) consisting of a dummy drive "missing" (why was this so hard to figure out!)

Now, a cat of /proc/mdstat will show your degraded raid devices are up and running

#cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdb5[1]
      979840 blocks [2/1] [_U]
md0 : active raid1 sdb1[1]
      192640 blocks [2/1] [_U]
md2 : active raid1 sdb6[1]
      159661888 blocks [2/1] [_U]
unused devices:

Note how one drive in all three cases is missing ("_") as opposed to up and running' ("U").

Creating the file systems and mount them

#mkfs.jfs /dev/md0

#mkfs.jfs /dev/md2
#mkdir /mntroot
#mkdir/mntboot
#mount /dev/md2 /mntroot
#mount /dev/md0 /mntboot

Fix up initrd

If you are using a SATA drive you pay attention!
edit /etc/mkinitrd/mkinitrd.conf and change:

MODULES=most

###MODULES=most
MODULES=dep

and

ROOT=probe

###ROOT=probe
ROOT="/dev/md2 jfs"

This tells init to use what it takes to boot off of a raid device not the /dev/sda device currently used.

Now run

#mkinitrd -o /boot/initrd.img-2.6.8-1-k7-smp-md 2.6.8-1-k7-smp

Edit /boot/grub/menu.lst

Copy the old listing below and paste it below:

title Debian GNU/Linux, kernel 2.6.8-1-k7-smp
root (hd0,0)
kernel /vmlinuz-2.6.8 root=/dev/sda6 ro
initrd /initrd.img-2.6.8
savedefault
boot

Now edit the new stanzas noting the changes in bold:

title Debian GNU/Linux, kernel 2.6.8-1-k7-smp -md Disk1 
root (hd0,0)
kernel /vmlinuz-2.6.8 root=/dev/ md2  ro
initrd /  initrd.img-2.6.8-1-k7-smp-md 
savedefault
boot

Now make a copy of the New stanza you just made and make the changes in bold:

title Debian GNU/Linux, kernel 2.6.8-1-k7-smp-md  Disk2 
root (hd 1 ,0)
kernel /vmlinuz-2.6.8 root=/dev/md2 ro      
initrd /initrd.img-2.6.8-1-k7-smp-md
savedefault
boot

Producing /etc/mdadm/mdadm.conf

edit /etc/mdadm/mdadm.conf
The top line in this example should be

DEVICE /dev/sda* /dev/sdb*

Then run:

mdadm --detail --scan >> /etc/mdadm/mdadm.conf

This should produce a proper file

Copy over everything to the degraded raid

#rsync -auHxv --exclude=/proc/* --exclude=/sys/* --exclude=/boot/* --exclude=/mntboot --exclude=/mntroot/ /* /mntroot/

#mkdir /mntroot/proc /mntroot/boot /mntroot/sys
#chmod 555 /mntroot/proc
#rsync -auHx   /boot/ /mntboot/

Make Changes in /mntroot/etc/fstab

Changes in bold

# /etc/fstab: static file system information.
#
# 
proc /proc proc defaults 0 0    
/dev/ md1  none swap sw 0 0    
/dev/ md0  /boot jfs defaults 0 2    
/dev/ md2  / jfs defaults,errors=remount-ro 0 1    
/dev/hda /media/cdrom iso9660 ro,user,noauto 0 0    
/dev/fd0 /media/floppy auto rw,user,noauto 0 0    
/dev/hda /cdrom iso9660 ro,user,noauto 0 0

Reboot

If it won't work you should be able to boot off of the old grub listing

At this point the box should be running off the degraded RAID1 devices on the second drive (/dev/sdb)

Check that everything works

If all is OK you should change the partition types of the first drive (/dev/sda)

- but you will lose all data!

Device	Size	Id	Eventual mount point
/dev/sda1	200M	fd	/boot/
/dev/sda5	1G	fd	swap
/dev/sda6	100G	fd	/

Attach the original drive's partitions to the existing (degraded) RAID arrays:

# mdadm /dev/md0 -a /dev/sda1

# mdadm /dev/md1 -a /dev/sda5    
# mdadm /dev/md2 -a /dev/sda6    
#cat /proc/mdstat     
   Personalities : [raid1]    
md0 : active raid1 sda1[0] sdb1[1]    
      192640 blocks [2/2] [UU]    
md1 : active raid1 sda5[0] sdb5[1]    
      979840 blocks [2/2] [UU]    
md2 : active raid1 sda6[2] sdb6[1]    
      159661888 blocks [2/1] [_U]    
      [ =====>..................]  recovery = 17.9% (28697920/159661888) finish=56.4min speed=38656K/sec
unused devices:

After a while all devices are in sync:

# cat /proc/mdstat     
Personalities : [raid1]  
md0 : active raid1 sda1[0] sdb1[1]    
    192640 blocks [2/2] [UU]  
md1 : active raid1 sda5[0] sdb5[1]    
    979840 blocks [2/2] [UU]  
md2 : active raid1 sda6[2] sdb6[1]    
    159661888 blocks [2/2] [UU]  
unused devices:

Regenerate initrd

Yes, this needs to happen again after the raid is complete!

#mkinitrd -o /boot/initrd.img-2.6.8-1-k7-smp-md 2.6.8-1-k7-smp  
(Is this still a needed step?)

Regenerate /etc/mdadm/mdadm.conf

edit /etc/mdadm/mdadm.conf
Delete all but the top line

DEVICE /dev/sda* /dev/sdb*

Then run:

mdadm --detail --scan >> /etc/mdadm/mdadm.conf

Your final file should look like:

DEVICE /dev/sda* /dev/sdb*    
ARRAY /dev/md0 level=raid1 num-devices=2  UUID=4d58ade4:dd80faa9:19f447f8:23d355e3    
 devices=/dev/sda1,/dev/sdb1

ARRAY /dev/md1 level=raid1 num-devices=2 UUID=3f1bdce2:c55460b0:9262fd47:3c94b6ab

 devices=/dev/sda5,/dev/sdb5    
ARRAY /dev/md2 level=raid1 num-devices=2 UUID=7dfd7fcb:d65245d6:f9da98db:f670d7b6    
 devices=/dev/sdb6,/dev/sda6

Configure grub to boot from both drives

Install the MBR on the second disk

#grub --device-map=/boot/grub/device.map
>> root (hd0,0)    
>> setup (hd0)    
>> root (hd1,0)    
>> setup (hd1)    
>> quit

Have Grub point to your MD root device. Note that things after the '#" symbol make a difference here (note to grub developers: this confuses people why not use a different delimiter?)

Edit /boot/grub/menue.lst 
## default kernel options for automagic boot options    
## If you want special options for specifiv kernels use kopt_x_y_z    
## where x.y.z is kernel version. Minor versions can be omitted.    
## e.g. kopt=root=/dev/hda1 ro    
# kopt=root=/dev/sd6 ro

## default kernel options for automagic boot options    
## If you want special options for specifiv kernels use kopt_x_y_z    
## where x.y.z is kernel version. Minor versions can be omitted.    
## e.g. kopt=root=/dev/hda1 ro    
# kopt=root=/dev/md2 ro

Setup the monitoring daemon

Just run:

dpkg-reconfigure mdadm

Test Test and Test

Test boot from both drives
Kill a drive and see if you get a email about the event.
Write up a step by step procedure to restore from a drive outage. (send a copy this way for this page!)
You should be all finished!
Please send notes of any typos/corrections to the email address below.
Special thanks to Onni Koskinen of Finland, whose gentle yet expert emails removed several glaring errors on this page and resulted in a vastly improved document.

Q/A

Re: section on configuring GRUB: will GRUB automatically boot from the good drive in the event of a disk failure?
Yes, IF you install Grub on both drives and your BIOS will roll over to the first bootable drive.

How do you see what is in a initrd file?

mount -o loop /tmp/myinitrd /mnt/myinitrd

From http://xtronics.com/reference/SATA-RAID-debian-for-2.6.html

inform@xtronics.com

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