SUMMARY: Backup while in multi-user mode

[Peter da Silva]

In article <1991May24.013214.2526 at servalan.uucp> rmtodd at servalan.uucp (Richard Todd) writes:
> 1. "dump" preserves the access times on files, and "restore" restores the
> files with the access times set correctly.  "cpio" neither records the access
> times in its archive nor leaves the access times of the files on disk 
> unaffected.  Thus, "cpio" screws up any schemes one may have for locating 
> user files that haven't been accessed in, say, 6 months and automatically
> moving them off to tape and deleting them.  

Your CPIO might have all those flaws. Ours doesn't. Ever hear of a program
by the name of "pax"?

> 2.  "dump" handles files with holes in them correctly (the holes don't take
> up space on the backup, and "restore" restores the files with holes correctly).
> "cpio" doesn't.  Having all your dbm files suddenly explode in disk usage 
> after having been brought back off of tape is considered bad form in some
> circles...

Again, a solved problem. (we don't use DBM, but our databases do have a
similar behaviour)

> 3.  Just how were you planning to do restores of those incremental backups?

We don't worry about deleted files reappearing, and it has not been a problem
in general. We do not restore en-masse from major disasters anyway... it's
always a good chance to tidy up old software, bring a system to the latest
rev level of everything, and so on.

> This means that you need to do 
> some extra work to make sure that all the stuff you got rid of once gets 
> gotten rid of again.

This is a minor problem compared to the complexity of shutting down all the
systems for the daily backups. I don't think we could work that way in any
case, as we usually back up a lot of systems remotely over the network.

> You can try to press "cpio" or "tar" into service as a backup program, but
> it's not really the same thing...

Until UNIX ships with a version of dump we can use, we don't really have an
alternative. I'm really surprised that anyone with any significant number of
machines is still using it.
-- 
Peter da Silva; Ferranti International Controls Corporation; +1 713 274 5180;
Sugar Land, TX  77487-5012;         `-_-' "Have you hugged your wolf, today?"