> a late night thought:
>
> why not intercept the write() system call?  if the write is to a file on
> the filesystem, keep track of its path in some kernel data structure.
> better yet, generate a /proc file with the pathnames of all filesystem
> files that were modified by write().
>
> the backup program would then read from this file and pop off the
> pathnames as they were backed up.  this would be implemented as a kernel
> module.

Hmm...not exactly the first thing that would have occured to me, but it's
definately possible.  This approach, however, shares the same problem as
most of the other schemes to keep track of modified files (like building a
list of timestamps/md5 sums or similar): What happens the second time you
backup a package?

If you only backup files modified in the current session, you're probably
going to overwrite (and loose) the files you modified earlier.  Let's say,
for instance, you just downloaded the latest release, and you modified
network.conf so your firewall works with your static IP.  You do a modified
files backup of etc and everythings great.  Next week, however, you need to
edit hosts.allow so you can access ssh from your office...what happens when
you do a modified backup of etc this time?  You need BOTH the modified
network.conf and the new hosts.allow...

There are ways around this (like generating a "master" file list for each
package, with date-stamps or md5 sums that never gets modified), but things
rapidly get ugly.

- How do you handle directories, for instance (remember, the file list for
etc doesn't include each and every file, it's basically just /etc).
- How do you support legacy packages that don't include a master list of
files?
- What if you find a package in more than one place (possible with the new
backup scripts)

I think the long-term solution to this is a package format that's designed
to build a complete filesystem from unmodified "core" packages and
configuration data.  I've headed towards this with my modifications of the
*.lrp packageing system, and David has taken some similar steps.  See some
of the recent threads on the leaf-developer list for anyone truly
interested.

Any/all thoughts on this welcome...especially crafty extensions to the
current packaging format!

Charles Steinkuehler
http://lrp.steinkuehler.net
http://c0wz.steinkuehler.net (lrp.c0wz.com mirror)



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