Hi,

Arnold Krille wrote on 2011-09-03 01:32:15 +0200 [Re: [BackupPC-users] Backing 
up slash partition]:
> On Saturday 03 September 2011 00:57:48 Timothy Murphy wrote:
> > Can one sensibly back up / with BackupPC?

the confusing thing about that question is that it is probably not what you
want to ask. Yes, you *can* back up your file systems from the root, though you
will *need* to exclude some things. No, bare metal recovery is not a feature
of BackupPC.

> The result you get is the same as if you would hard power-off your machine
> and restart it. Or take out one drive in your raid1 while its running.

Well, no. Firstly, you don't get a snapshot, unless you actually back up a
snapshot, i.e. your hard power-off will have occurred at different points in
time for different parts of your file systems - maybe even spread out across
several hours. It will likely be inconsistent. That is usually not that much
of a problem (maybe because nobody does it), but you *should* consider whether
it is in your case.

Secondly, while you do get an "image" of your system, you need to think about
what you would want to do with it. You can't press a button and get a disk as
result that you can insert into a replacement machine. At the *very least*,
you will need to set up partitioning the target disk, creating the file
system(s), and boot loading. All of this is information that is stored on your
disk, but outside the file systems. Additionally, your system will be
configured for the hardware it was running on. Your replacement may or may not
have different requirements. For example, it's very likely that udev will name
your network interfaces differently, which can be a major nuisance.

Chances are, you will find it easier to reinstall a system from original
source media and then restore meaningful data and configuration from your
backups. If so, there's not much point in backing up all the binaries (and,
say, your WWW proxy's cache). You might say, "if I backup everything, it won't
turn out that I forgot something". True, but you might also find that it has
some merit to be aware which of your data is valuable and which isn't.

> You should make sure you don't cross mount-points though. Otherwise the
> backup of localhosts '/' will recurse into itself.

How that?

Les Mikesell wrote on 2011-09-02 18:36:11 -0500 [Re: [BackupPC-users] Backing 
up slash partition]:
> On Fri, Sep 2, 2011 at 5:57 PM, Timothy Murphy <gayleard AT eircom DOT net> 
> wrote:
> > Can one sensibly back up / with BackupPC?
> 
> Sure, but if you don't use --one-file-system in the options, be sure
> to exclude the pseudo mounts like /proc, /sys (and maybe /dev,
> depending on the version).

To elaborate, you *need* to exclude /proc (and possibly /sys), else your
backup will probably not complete. In the very least, it will contain
large amounts of meaningless data (like your kernel core image).

Regardless of the version, backing up /dev seems to be pointless. Unless it is
both static (does *anyone* still use a static /dev?) and you *really* plan to
recover your machine from the backup.

What I'd further recommend excluding is /tmp and /media (or whatever your
system automatically mounts removable media to). It's always difficult to
anticipate everything that might cause problems. This is the real downside of
a "backup everything except ..." approach.

Another point to consider would be database files, which generally don't
handle non-snapshot image level backups particularly well. You might need
additional steps (like dumping the database from a DumpPreUserCmd) if you
have software like databases running.

So, my answer to your question is, "yes, but I wouldn't recommend it".

Regards,
Holger

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