In a message dated: Fri, 26 Oct 2001 10:42:31 EDT
Ted Grzesik said:
>Hi folks,
>
>I have a question about backups.
>
>I have a RedHat 7.1 system using Software RAID-1 filesystems.
>
>QUESTION: What is the best method of performing backups of the root
>filesystem? I want something that will give me a perfect copy that
>could be restored.
>
>Option 1:
>Normally, I would use my PowerQuest DriveImage software (similar to
>Norton Ghost), but the problem is, it doesn't recognize the RAID
>partitions (it knows Linux ext2 though).
Well, that's not really a solution/option then, is it :)
>Option 2:
>My memory from my HP-UX days says to use 'cpio', BUT...
>I tried that last night and got spurious errors about 'Truncating inode
>number'. That didn't give me a very comfortable feeling about my backup.
cpio is an option, but I wouldn't rate it in the top 10 of all
possible options :)
>QUESTION: Should I 'init 1' to force single-user mode? This would
>minimize open files during the backup.
You could, though I never do. I run backups of our servers here
while in run level 3/5. There is the problem of open files, but
since we do nightly incrementals, and we do them at very off hours,
this is minimized. Of course, since the backups are over the
network, I don't have much choice but to remain in level 3/5.
>Option 3:
>I could use 'tar', but that is not what I would consider a "perfect" backup.
You'd be surprised. Gnu tar is vastly superior to just about every
vendor written version of tar out there. To the point where it's
actually a better alternative in many instances.
>Option 4:
>I have another identical disk to my two RAID enabled disks. I could
>pull one disk out of the array, swap in the empty one and force a RAID
>rebuild. In essence, giving me a truly perfect backup.
Well, that completely depends upon what kind of RAID you're running.
If you've running a RAID 1 set, then yes, you'd have a true backup,
but if you're running RAID 0, or a concatenation scheme, then that
won't work at all.
>BTW, you may be wondering why I'm so worried about backups... I am
>about to upgrade to RedHat 7.2 and want a fallback position in case
>things go horribly wrong.
Personally, my preferred method of protecting against this is a
two-fold approach.
1. When initially installing any system create separate
partitions for any location where you're like to change
data. For example, /home and /usr/local are always
separate partitions from /, /boot, /usr, and /var
(all of which may or may not be separate or different
partitions).
2. When upgrading, copy all system files you care about to
a file system such as /usr/local or /home
(I'll often keep system files in /usr/local/etc and
sym-link them to /etc).
Once you know all data that you care about is on a
separate partition, RE-INSTALL with the new version
of the OS. That means actually go through the install
procedure and re-format the very partitions you're old
OS was installed on. I shouldn't have to point out
the obvious here, but I will:
DO NOT FORMAT /home or /usr/local!
Again, in case you didn't quite get that:
DO NOT FORMAT /home or /usr/local!
I don't believe in "upgrading" an OS. Every OS I've ever used has
caused me problems when trying to upgrade. Windows, Linux, Solaris,
all of them. Sure, sometimes it might work. But Murphy will always
be right behind you waiting to make sure at least one thing gets
hosed up.
My method allows for 2 things:
1. You don't really need to do a backup
(however, I highly recommend it in case you accidently
missed what I tried to so clearly spell out above :)
2. You are never left with any crap on your system from the
previous install which could cause you problems later on.
Another thing this method allow for is the chance to switch to a
different distribution in case you want to try something else like
Debian or Mandrake, etc. All linux distros will recognize your ext2
partitions, you just need to set up the /etc/fstab file correctly
to make sure your personal data gets mounted at boot time.
Btw, this scheme is intended for home environments where one can not
afford the luxury of large detached RAID boxes, huge capacity tape
backup, etc. We do not run our servers like this at MCLX. If we
need to upgrade an OS, we usually build an entirely new system and
swap out the old one.
Hope that helps!
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