Francois Marier: Setting up RAID on an existing Debian/Ubuntu installation
I run RAID1 on all of the machines I support. While such hard disk mirroring is not a replacement for having good working backups, it means that a single drive failure is not going to force me to have to spend lots of time rebuilding a machine.The best possible time to set this up is of course when you first install the operating system. The Debian installer will set everything up for you if you choose that option and Ubuntu has alternate installation CDs which allow you to do the same.
This post documents the steps I followed to retrofit RAID1 into an existing Debian squeeze installation. Getting a mirrored setup after the fact.
OverviewBefore you start, make sure the following packages are installed:
Then go through these steps:apt-get install mdadm rsync initramfs-tools
- Partition the new drive.
- Create new degraded RAID arrays.
- Install GRUB2 on both drives.
- Copy existing data onto the new drive.
- Reboot using the RAIDed drive and test system.
- Wipe the original drive by adding it to the RAID array.
- Test booting off of the original drive.
- Resync drives.
- Test booting off of the new drive.
- Reboot with the two drives and resync the array.
1- Partition the new driveOnce you have connected the new drive (/dev/sdb), boot into your system and use one of cfdisk or fdisk to display the partition information for the existing drive (/dev/sda on my system).
The idea is to create partitions of the same size on the new drive. (If the new drive is bigger, leave the rest of the drive unpartitioned.)
Partition types should all be: fd (or "linux raid autodetect").
2- Create new degraded RAID arraysThe newly partioned drive, consisting of a root and a swap partition, can be added to new RAID1 arrays using mdadm:
and formatted like this:mdadm --create /dev/md0 --level=1 --raid-devices=2 missing /dev/sdb1
mdadm --create /dev/md1 --level=1 --raid-devices=2 missing /dev/sdb2
Specify these devices explicitly in /etc/mdadm/mdadm.conf:mkswap /dev/md1
mkfs.ext4 /dev/md0
and append the RAID arrays to the end of that file:DEVICE /dev/sda* /dev/sdb*
You can check the status of your RAID arrays at any time by running this command:mdadm --detail --scan >> /etc/mdadm/mdadm.conf
dpkg-reconfigure mdadm
cat /proc/mdstat
3- Install GRUB2 on both drivesThe best way to ensure that GRUB2, the default bootloader in Debian and Ubuntu, is installed on both drives is to reconfigure its package:
and select both /dev/sda and /dev/sdb (but not /dev/md0) as installation targets.dpkg-reconfigure grub-pc
This should cause the init ramdisk (/boot/initrd.img-2.6.32-5-amd64) and the grub menu (/boot/grub/grub.cfg) to be rebuilt with RAID support.
4- Copy existing data onto the new driveCopy everything that's on the existing drive onto the new one using rsync:
mkdir /tmp/mntroot
mount /dev/md0 /tmp/mntroot
rsync -auHxv --exclude=/proc/* --exclude=/sys/* --exclude=/tmp/* /* /tmp/mntroot/
5- Reboot using the RAIDed drive and test systemBefore rebooting, open /tmp/mntroot/etc/fstab, and change /dev/sda1 and /dev/sda2 to /dev/md0 and /dev/md1 respectively.
Then reboot and from within the GRUB menu, hit "e" to enter edit mode and make sure that you will be booting off of the new disk:
Once the system is up, you can check that the root partition is indeed using the RAID array by running mount and looking for something like:set root='(md/0)'
linux /boot/vmlinuz-2.6.32-5-amd64 root=/dev/md0 ro quiet
/dev/md0 on / type ext4 (rw,noatime,errors=remount-ro)
6- Wipe the original drive by adding it to the RAID arrayOnce you have verified that everything is working on /dev/sdb, it's time to change the partition types on /dev/sda to fd and to add the original drive to the degraded RAID array:
You'll have to wait until the two partitions are fully synchronized but you can check the sync status using:mdadm /dev/md0 -a /dev/sda1
mdadm /dev/md1 -a /dev/sda2
watch -n1 cat /proc/mdstat
7- Test booting off of the original driveOnce the sync is finished, update the boot loader menu:
and shut the system down:update-grub
before physically disconnecting /dev/sdb and turning the machine back on to test booting with only /dev/sda present.shutdown -h now
After a successful boot, shut the machine down and plug the second drive back in before powering it up again.
8- Resync drivesIf everything works, you should see the following after running cat /proc/mdstat:
indicating that the RAID array is incomplete and that the second drive is not part of it.md0 : active raid1 sda1[1]
280567040 blocks [2/1] [_U]
To add the second drive back in and start the sync again:
mdadm /dev/md0 -a /dev/sdb1
9- Test booting off of the new driveTo complete the testing, shut the machine down, pull /dev/sda out and try booting with /dev/sdb only.
10- Reboot with the two drives and resync the arrayOnce you are satisfied that it works, reboot with both drives plugged in and re-add the first drive to the array:
Your setup is now complete and fully tested.mdadm /dev/md0 -a /dev/sda1
Ongoing maintenanceI recommend making sure the two RAIDed drives stay in sync by enabling periodic RAID checks. The easiest way is to enable the checks that are built into the Debian package:
but you can also create a weekly or monthly cronjob which does the following:dpkg-reconfigure mdadm
Something else you should seriously consider is to install the smartmontools package and run weekly SMART checks by putting something like this in your /etc/smartd.conf:echo "check" > /sys/block/md0/md/sync_action
These checks, performed by the hard disk controllers directly, could warn you of imminent failures ahead of time. Personally, when I start seeing errors in the SMART log (smartctl -a /dev/sda), I order a new drive straight away./dev/sda -a -d ata -o on -S on -s (S/../.././02 L/../../6/03)
/dev/sdb -a -d ata -o on -S on -s (S/../.././02 L/../../6/03)
Continuing my series about my 
but you ll be traveling the world while reading him.
My questions are in bold, the rest is by Christian.
Who are you?
I am a French citizen (which is easy to guess unless you correct my
usual mistakes in what follows). I m immensely proud of being married
for nearly 26 years with Elizabeth (who deserves a statue from Debian
for being so patient with my passion and my dedication to the
project).
I m also the proud father of 3 wonderful kids , aged 19 to
23.
I work as team manager in the Networks and Computers Division of Onera
the French Aerospace lab , a public research institute about
Aeronautics, Space and Defense. My team provides computer management
services for research divisions of Onera, with a specific focus put on
individual computing.
I entered the world of free software as one of the very first users of
Linux in France. Back in the early 1990 s, I happened (though the BBS
users communities) to be a friend of several early adopters of Linux
and/or BSD386/FreeBSD/NetBSD in France. More specifically, I
discovered Linux thanks with my friend Ren Cougnenc (all my free
software talks are dedicated to Ren , who passed away in 1996).
You re not a programmer, not even a packager. How did you come
to Debian?
I m definitely not a programmer and I never studied computing (I
graduated in Materials Science and worked in that area for a few years
after my PhD).
However, my daily work always involved computing (I redesigned the
creep testing laboratory and its acquisition system all by myself
during my thesis research work). An my hobbies often involved
playing with home computers, always trying to learn about something
new.
So, first learning about a new operating system then trying to
figure out how to become involved in its development was quite a
logical choice.
Debian is my distro of choice since it exists. I used Slackware on work
machines for a while, but my home server, kheops,
first ran Debian 1.1 when I stopped running a BBS on an MS-DOS machine
to host a news server. That was back in October 1996.
I then happened to be a user, and more specifically a user of
genealogy software, also participating very actively in Usenet from
this home computer and server, that was running this Debian thing.
So, progressively, I joined mailing lists and, being a passionate
person, I tried to figure out how I could bring my own little
contribution to all this.
This is why I became a packager (yes, I am one!) by taking over the
geneweb package, which I was using to publish my genealogy
research. I applied as DD in January 2001, then got my account in July
2001. My first upload to the Debian archive occurred on August 22nd
2001: that was of course geneweb, which I still maintain.
Quite quickly, I became involved in the work on French localization. I
have always been a strong supporter of localized software (I even
translated a few BBS software back in the early 90 s) as one of the
way to bring the power and richness of free software to more users.
Localization work lead me to work on the early version of Debian
Installer, during those 2003-2005 years where the development of D-I
was an incredibly motivating and challenging task, lead by Joey Hess
and his inspiring ideas.
From user to contributor to leader, I suddenly discovered, around
2004, that I became the coordinator of D-I i18n (internationalization)
without even noticing 
I'm surprised to be on the porch hearing rushing water. I tend to think
of up here as high and mostly dry, but not this time of year. Yesterday
was such a soaking rain, very annoying at the time as I did chores and
drove out from town. Now there are two little creeks here. That's a sound
I've missed..
Pity that all the water is going to waste. I discovered the reason the large
cistern is not filling up is simply because the pipe into it is not connected
to the feeder pipe in the spring. It seems like a complete shambles really,
with layer upon layer of pipes, all broken. I will have to wait until the
water is down to dig and find out what's going on, and fix it.
In the last of the evening light today I got the house's two battery banks
finally combined into one bank. I had planned this out long ago, and bought one
long cable I'd need, so was surprised to find I needed two long cables. Had to
slide batteries around like a big sokoban puzzle, and swap several cables to
make it work. While I was away I'd charged up the bank that had gone unused
most of the winter. So they were near equalized and the combination seems to
have gone ok. I got through the lean part of the year with only half the
batteries; there never seemed to be a good time to combine them. It remains to
be seen if the solar panels can keep my increased capacity filled.
I hope this was only an early taste of spring. Would be nice to have some
more icy weather so I can put off dealing with refrigeration a little while
longer. I have my eye on a 12v/propane fridge.
...For the cases where, yes, you actually do want it.
For the impatient
assuming you're in a clean checkout on the tip of your current branch:
Time for a fifth Debian XSF News issue!
Not only that it took 4 years to fix 
So I guess I just drop Triaging for week 13, 14 and maybe 15
Now the bugs I triaged just before :
There s a lot of exciting activity going on around libraries at the moment. One of them is the 
Wow, that was a night. I'm still quite tired from the weekend. Someone
told me, that ~ 1 000 people subscribed to our live denting via