kevin at ie.suberic.net
Sun Dec 2 15:46:31 GMT 2012
tl;dr: I'm curious about the best way to have a regularly cloned
backup boot disk on an Ubuntu 12.04 system.
I have an HP microserver with 4 internal disks and a 5th, external,
boot disk. The microserver provides one esata port and six usb ports.
The boot drive is on the external esata port and I have three possible
backup disks that I can boot with if the current boot disk fails. So
a quick cast of characters:
/dev/sd[abcd]: internal data disks. They get backed up a different way.
/dev/sde: external esata disk.
/dev/sde1: /boot on a primary partition
/dev/sde2: An extended LVM partition with / and swap on it (and 50G of
free space for snapshots)
I can connect any of my backup disks with USB (and if being used as a
primary, with esata). Let's say I just connect 1 and it comes up as
/dev/sde. The backup disks are all different sizes. I can't just dd
the entire disk across - nevermind that it's horribly inefficient.
I figure I can do the following:
Partition /dev/sde to match - a /dev/sde/1 primary and /dev/sde2 with
LVM and similar size partitions (obviously with different free space
due to drive size differences). Note it will need a different VG name.
The general backup steps will be:
1. Mount snapshot volume of /dev/mapper/frith-root on /mnt/source
2. Mount /dev/mapper/frith2-root /mnt/target
3. rsync only source -> target.
4. Unmount target and the snapshot volume.
5. Mount /dev/sde1 /mnt/target
6. rsync only /boot -> target
7. Unmount target.
The issue is, will the resulting /dev/sdf be bootable? I would imagine
Scenario 1: The esata disk remains plugged in, is identified as
/dev/sde and is not bootable. BIOS moves on to USB and tries to boot
off /dev/sdf. Will grub understand what to do here or will it try to
boot or mount things on /dev/sde?
Scenario 2: The esata disk is either disconnected or not seen. The
backup disk is now /dev/sde.
Either way, the backup disk has a slightly different LVM config (the
VG name is different and the filesystems have different UUIDs).
Is there a grub command I can run on the backup disk that will make it
a bit more device independent? I'm looking but generally grub docs
annoy the crap out of me so if anyone has a magical idea here...
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