Backup, what system files are *really* important?

[Stuart McGraw]

On 03/11/2010 06:07 PM, Mike McCarty wrote:
> Patrick O'Callaghan wrote:
>> On Thu, 2010-03-11 at 18:29 -0600, Mike McCarty wrote:
>>> Patrick O'Callaghan wrote:
>>>> I back up all of /etc and /usr/local. Also /opt if it exists.
>>> Is /opt really likely to contain some configuration information
>>> that a reinstall wouldn't set up? ISTM that, if the system
>>> is "modern" enough to use /opt for its install, then its config
>>> would also be in /var. Not so?
>> 
>> /opt (and /usr/local) are likely to contain stuff that wasn't installed
>> via rpm or yum, thus needs to be preserved. That's all. YMMV.
> 
> Ok, that corresponds to my thinking. So, anything in /opt either
> isn't part of the *system* backup but part of the *data only*
> backup, and doesn't configure the system, or if Fedora decides
> to start putting some stuff in there, then I think the config
> would go into /var.
> 
> That's why I listed /opt as "not necessary" for a *system only*
> backup. I would put it on *data only* backups, as defined by
> the OP, since it shouldn't contain any configuration data used
> by the OS, as opposed to later installed stuff not necessary for
> boot, mounting NFS, DHCP, SELinux setup, etc.

Yes, the above is consistent with my intent too.
In my OP I meant "user" files in a very general sense
to be anything created independently (roughly) of stuff installed
from Fedora or 3rd party software packages, which would include 
things I put in /usr/local, /opt, etc.  I have relatively little 
software in either of those directories and I keep the distribution
packages for them along with build notes so they can be reinstalled
if necessary.

Since my backup media is DVD, I am trying to limit the 
size of backups by not backing up stuff that can be restored
from other sources and most of the system files seem to
be in that category.  But I don't want to be so nit-picky
that I screw myself and have to do a full reinstall when
that could have been avoided had I had a backup copy of file
X.

Thanks for all the suggestions.