script for on-disk configuration file backup

["Steve M. Robbins" <steven.robbins@videotron.ca>]

Hi,

A couple days after first installing debian a couple years back, I
managed to mess up the passwd file in some way.  I was very pleasantly
surprised to find a backup version of the file on-line in /var/backups.
I was quickly able to un-do whatever it was that I did.

There are also backups of dpkg.status, inetd.conf, and a few others.
At the time, I wondered why backup copies of *all* the config files in
/etc aren't automatically saved.  There have been times that I
wondered "did the configuration of foo change in the last two weeks?".
I have tapes, of course, but finding the tape that holds /etc for the
correct date is a bit more work than I'm willing expend.  Often, I
don't even _know_ what date I'm after.

A couple months back, I was upgrading packages as I often do.
Packages will silently update their conffiles if you haven't changed
them, which is proper.  One package --- which shall remain nameless to
protect the guilty :-) --- changed the colour scheme of my email
client to a contrastless grey letters on a grey background.  I had to
mess around a bit to get it back to how it was.  That was the straw
that made me finally write up the cron script to back up all my
configuration files on-disk.

The script, below, really has two functions.  One is to make a 
backup copy of any changed file in /etc.  I used "savelog" to
keep the last few revisions of the files.  The second function
is to keep /etc a little more tidy.  The script deletes all editor
backup files (*~), and notifies me when there is a .dpkg-new or
.dpkg-old copy lying about.  I run this in cron.daily, so I keep
getting reminders until I go in and clean these up by hand.

After running this for a few months, I've discovered that some
packages make their own backup copies of config files.  Setserial, for
example backs up /etc/serial.conf to /etc/.serial.conf.old.  I've
put exceptions in to ignore the ones I've found.  The script 
also ignores the cache files ld.so.cache, mtab, and adjtime.

I'm posting the script here, for two reasons.  First, I'd appreciate
knowing if there's a better way to accomplish this.  Maybe it is
handled in some package of which I am unaware?  On the other hand, if
this is not already handled somewhere, others might benefit.  Perhaps
this approach could be integrated into a package somewhere.


#!/bin/sh
#
# Save a copy of any file in /etc that has been changed.

set -e

IDIR=/etc
BDIR=/var/local/backups

test -d $BDIR || mkdir -p -m755 $BDIR
cd $BDIR

for file in `find $IDIR -type f`; do

    case $file in
	*~) rm $file; continue;;
	/etc/modules.conf.old) continue;;
	/etc/.serial.conf.old) continue;;
	/etc/sgml/*.old) continue;;
	/etc/webmin/webmin.acl.bak) continue;;
	*bak|*.dpkg*|*.old) echo "Check $file"; continue;;
	/etc/ld.so.cache|/etc/mtab|/etc/adjtime) continue;;
    esac

    # do nothing if file is empty
    test -s $file || continue

    if [ -e ./$file ]; then
	cmp -s $file ./$file && continue
	savelog -c 15 ./$file >/dev/null
    else
	dir=`dirname $file`
	test -d ./$dir || mkdir -p ./$dir
    fi
    cp -p $file ./$file
done




-- 
by Rocket to the Moon,
by Airplane to the Rocket,
by Taxi to the Airport,
by Frontdoor to the Taxi,
by throwing back the blanket and laying down the legs ...
- They Might Be Giants