Hi Paul,
I've used the Disk Utility and created a copy that boots. Thank you
it was fun. I haven't done the cron thing yet or the psync over it.
One question, it appears like everything on the restore copy is
exactly the same, however the total file size and the total number of
files is off by about 1%. Maybe Disk Utility is smart enough not to
copy items in the Trash Can or maybe there is something else going on?
Joe.
On Aug 10, 2005, at 2:27 AM, Paul McCann wrote:
Hi Joe,
... I wrote a little program that creates a new directory each
time (ie, 2005-08-09) and does a full backup using psync to the
directory.
My question: In the event of a hard disk failure, will I be able
to boot from a full copy in a directory? How would I be able to
recover?
Probably not, but it's not too hard to make bootable copies. Just
partition your backup drive so that you have a partition for each
backup copy that you'd like to keep (I tend to "roll" three, so
that at any time I have the last 2-3 days of live backups). Then
use the Disk Utility to clone a copy of your "live" system onto as
many copies as you wish to keep. It takes about 30 minutes to clone
mine, but it's obviously pretty sensitive to the size of your live
system. This process will produce bootable copies, but you probably
don't want to be doing this all the time. My strategy is to get
psync to synchronise each of the backups in turn, instituted via a
cron job.
Anyway, in more detail:
(1) Make some appropriately sized partitions, so that each will be
capable of taking a full copy of your live system. Allow some room
for expansion. Disk Utility makes this easy.
(2) For each partition: firstly erase the existing contents (takes
about 5 seconds in Disk Utility), in the "Erase" tab. I think you
can also click a button in the Restore tab (see below), but I've
never gone that route. In any case, erasing any existing stuff is
crucial to success.
(3) Go to the restore tab and drag your live system into the
"Source" text field and your first clean partition into the second
(destination) source field. Click restore, enter admin password,
and wait! Repeat as you will.
You might like to test the bootability at this point: I've not had
a problem with this technique.
That done you can just set psync to consecutively roll through
synchronising with the backups in turn. The entries in the crontab
(/etc/crontab) should be something like
# minute hour mday month wday who command
15 4 * * 3,5 root /usr/local/bin/
psync -q -d / /Volumes/backup2 >> /Users/pmccann/psync_output_2 2>&1
15 4 * * 2,4,6 root /usr/local/bin/
psync -q -d / /Volumes/backup3 >> /Users/pmccann/psync_output_3 2>&1
Obviously that's for a rolling pair of backups on the imaginatively
named /Volumes/backup2 and /Volumes/backup3. Iterate as necessary
and adjust the wday fields. The files "psync_output_2" etc will
contain anything to STDOUT or STDERR from the process. In practice
I just check that things have run OK by tailing those files and/or
checking their modification date.
Anyway, the upshot of this is that the backups always maintain
their bootability. I've even --inadvertantly-- bumped the system
version of the backups (10.3 => 10.4) using this synchonization
technique; didn't cause any difficulties, and bootability remains.
Best wishes,
Paul
