Imaging a running Linux server

[Bill Bogstad]

On Sun, Aug 29, 2010 at 10:43 AM, Edward Ned Harvey <blu-Z8efaSeK1ezqlBn2x/YWAg at public.gmane.org> wrote:
>> From: discuss-bounces-mNDKBlG2WHs at public.gmane.org [mailto:discuss-bounces-mNDKBlG2WHs at public.gmane.org] On
>> Behalf Of Bill Bogstad
>>
>> I do NOT recommend imaging a mounted filesystem with dd from an active
>> partition (and possibly a LVM snapshot of such a partition).   Even a
>> LVM snapshot (by itself) does not guarantee that the "on-disk" data is
>> in a consistent state.
>
> This is true, however, as long as you create a snapshot and then backup (via
> dd or dump) then you'll be fine to the extent your system is able to survive
> an unexpected power cycle or kernel panic.

And how many of of us routinely power down computers by yanking the
power plug?  It would certainly be faster then going through the
normal shutdown procedure.

Admittedly with journaling filesystems (ext3+, reiserfs, xfs),
catastrophic loss is less likely.   I have a Dell desktop which locks
up every couple of months and I end up having to cycle the power on
it.[1] That doesn't mean that when I install a new kernel, I reboot
with the power switch.  If you have no choice, sure, you can image a
snapshot of a live filesystem.   But if at all possible find another
way.

Bill Bogstad

[1] I've run memory diagnostics multiple times with no luck.  I've
even run Dell's system diagnostics as well with no errors found.   The
system is getting old enough that I'll probably just replace it.