[ILUG] Backing up debian

[Rick Moen]

Quoting Colin O'Keeffe (ilugcolin at gmail.com):

> Is there a way to backup important debian files like X settings and
> kernel image incase I break something ?

Well, I sometimes make a safety copy of /etc like this:

# cd /etc
# tar cvzf etc-$(date --iso-8601).tar.gz /etc

The resulting tarball's tiny enough to fit on {shudder} a floppy, if
need be.

I'm not clear on why you'd need/want to keep a copy of a kernel _image_.
You would certainly want to keep a copy of your kernel .config file, if
you compile your own.

What you might want to make a safety copy of is your current list of
installed packages:

     # dpkg --get-selections >selections.txt

And get their current versions:

     # COLUMNS=150 dpkg -l > packages.txt

> Also , where is the package list stored on a machine or does it fetch
> it from the server ?

The _available_ packages list is stored as text file
/var/lib/dpkg/available, mashed down from the individual package
repositories' Packages[.gz] files fetched to /var/lib/apt/lists .  
(There's also a binary index somewhere to speed up reads, generated
dynamically as needed.)  The _installed_ packages are recorded in
/var/lib/dpkg/status -- and I believe that's likewise hashed
dynamically, somewhere.

But doing the above commands, honestly, gets you what you need to make a
copy of.  Because, given "selections.txt", you can rebuild your system, 
not including local customisations and data files, from a minimal Debian
Base System install plus this:

# dpkg --set-selections <selections.txt
# apt-get -u dist-upgrade
  (or maybe "apt-get dselect-upgrade" might be better -- same idea,
  anyway)