Skip to content

Instantly share code, notes, and snippets.

@joshenders

joshenders/mdsetup.md

Last active November 19, 2023 19:04
Show Gist options
  • Star 2 You must be signed in to star a gist
  • Fork 0 You must be signed in to fork a gist
  • Save joshenders/3803617 to your computer and use it in GitHub Desktop.
Save joshenders/3803617 to your computer and use it in GitHub Desktop.
Download ZIP
Create mdraid mirror from an existing Wheezy installation
Raw
mdsetup.md

Create mdraid mirror from an existing Debian installation

Throughout this guide, /dev/sda will be referred to as the old drive and /dev/sdb will be referred to as the new drive. If possible, I suggest disconnecting all other disks attached to the system while performing this maintenance.

Prerequisite software

apt-get install mdadm rsync

1. Partition the new drive.

sfdisk -d /dev/sda | sfdisk /dev/sdb 
sfdisk --change-id /dev/sdb 1 DA # change partition-type to, "0xDA" aka "non-fs data" as "linux raid auto" is deprecated

2. Create degraded RAID array.

mdadm --create /dev/md0 --level=1 --raid-devices=2 missing /dev/sdb1 # md/v1.x metadata okay if grub-pc version is 1.98+20100720-1 or later [3]
mkfs.ext4 /dev/md0
mdadm --detail --scan >> /etc/mdadm/mdadm.conf
dpkg-reconfigure mdadm

3. Copy existing data onto the new drive.

mkdir /tmp/destroot
mount /dev/md0 /tmp/destroot
rsync -auHxv --exclude=/proc/* --exclude=/sys/* --exclude=/tmp/* /* /tmp/destroot/

4. Update initramfs and install bootloader on both drives

mount -o bind /dev /tmp/destroot/dev 
mount -t proc none /tmp/destroot/proc 
mount -t sysfs none /tmp/destroot/sys
chroot /tmp/destroot /bin/bash
update-initramfs -u -k all
rm /boot/grub/device.map
update-grub
grub-install /dev/sda
grub-install /dev/sdb
blkid /dev/md0 # replace UUID line in /etc/fstab (in chroot)
exit

5. Reboot. Boot into the degraded array (new drive) and test system.

reboot # Pivot bios boot order to boot to new drive (/dev/sdb) 
mount | grep $(blkid -o value /dev/md0 | head -n1) # verify booted from "/dev/md0".

6. Add original drive to the degraded array and resync.

sfdisk --change-id /dev/sda 1 DA # change partition-type to, "0xDA" aka "non-fs data" as "linux raid auto" is deprecated
mdadm /dev/md0 -a /dev/sda1
watch -n1 cat /proc/mdstat

7. Test booting off of the old drive (/dev/sda). Simulate failure by disconnecting new drive (/dev/sdb).

poweroff # Verify bios boot to old drive (/dev/sda). Preferably BIOS handles this failover automatically.
mount | grep $(blkid -o value /dev/md0 | head -n1) # verify booted from "/dev/md0".
poweroff

8. Reconnect new drive (/dev/sdb) and resync drives.

mdadm /dev/md0 -a /dev/sdb1
watch -n1 cat /proc/mdstat

9. Test booting off of the new drive (/dev/sdb). Simulate failure by disconnecting old drive (/dev/sda).

poweroff # Verify bios boot to "/dev/sdb". Preferably BIOS handles this failover automatically.
mount | grep $(blkid -o value /dev/md0 | head -n1) # verify booted from "/dev/md0".
poweroff

10. Reconnect old drive (/dev/sda) and resync drives.

mdadm /dev/md0 -a /dev/sda1
watch -n1 cat /proc/mdstat

11. Reboot with the two drives

reboot
mount | grep $(blkid -o value /dev/md0 | head -n1) # verify booted from "/dev/md0"

References

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment