I manage a set of CentOS operations workstations which are all clones of each other (3 "live" and 1 "spare" kept powered down); each has a single drive with four partitions (/boot, /, /home, swap). I've already set up cron'd rsync jobs to copy the operations accounts between the workstations on a daily basis, so that when one fails, it is a simple, quick process to swap in the spare, restore the accounts from one of the others, and continue operations. This has been successfully tested in practice on more than one occasion.
However, when I perform system updates (about once a month), I like to create a temporary "clone" of the system to an external drive before running the update, so that I can simply swap drives or clone back if something goes horribly wrong. I have been using "CloneZilla" to do this, but it can take a while since it blanks each partition before copying, and requires a system shutdown.
Question 1: Would it be sufficient to simply use CloneZilla once to initialize the backup drive (or do it manually, but CloneZilla makes it easy-peasy), and then use "rsync -aHx --delete" (let me know if I missed an important rsync option) to update the clone partitions from then on? I am assuming that the MBR typically doesn't get rewritten during system updates, though "/etc/grub.conf" obviously does get changed.
Suppose I want to store more than one workstation on a single drive (easy), and be able to boot into any of the stored configurations (hard). Here's what I thought of: 1) Create a small "master" partition which contains a bootloader (such as a CentOS rescue disk), and a single "swap" partition. 2) Create one partition "set" per workstation (/boot, /, /home, excluding swap). Obviously, these will all likely be logical, and each workstation must use unique labels for mounting partitions. 3) On the "master" partition, modify the bootloader menu to allow one to chainload the /boot partitions for each configuration. (This is the "Voila!" step that I haven't fully figured out.)
Question 2: Is there a better way to do the above? How do I perform the "Voila!" step, i.e. what's the right chainload command for this? Also, the chainloaded partitions are logical; is this OK?
I also have a single off-site NAS disk which contains clones of all the critical workstations on-site. Most of them are Macs, so I can use sparseimages on the NAS for the clones and get easy-peasy incremental clones. I also do this for the Linux box (backing it up incrementally to an HFS case-sensitive sparseimage via rsync), but it's (obviously) a bit of a kludge.
Question 3: Is there a UNIX equivalent to the Mac sparseimage that I should be using for this? ("tar -u" can do it (duh), but then the backup file grows without bound.)
Thanks, -G. -- Glenn Eychaner (geychaner@lco.cl) Telescope Systems Programmer, Las Campanas Observatory