Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!bu-cs!encore!bzs
From: bzs@Encore.COM (Barry Shein)
Newsgroups: comp.unix.wizards
Subject: Re: GNU-tar vs dump(1)
Message-ID: <4559@xenna.Encore.COM>
Date: 3 Jan 89 00:42:52 GMT
References: <17999@adm.BRL.MIL>
Organization: Encore Computer Corp, Marlboro, MA
Lines: 36
In-reply-to: nvt9001@BELVOIR-EMH3.ARMY.MIL's message of 2 Jan 89 16:03:37 GMT
Posting-Front-End: GNU Emacs 18.41.15 of Tue Jun  9 1987 on xenna (berkeley-unix)


From: nvt9001@BELVOIR-EMH3.ARMY.MIL (DoN Nichols)
>	Can anyone out there in wizard-land tell me any reason why I
>should continue to use dump(1) for system backups given the capabilities
>in the latest release of tar(1) from GNU?

I haven't really looked at gnutar (it sounds very good from your
description so I'll go look at it, thanks :-) but one thing I would
look out for is whether or not DELETIONS are saved on backups,
particularly incrementals.

What this means (in practice) is that if a backup procedure doesn't
backup deletions then files deleted between fulls and incrementals or
two incrementals will reappear when the file system is restored.
Another way of stating this is whether the state of the directory's
contents are restored or just added to.

The worst effect, for most folks, is when this pushes the partition
over 100% and you can't complete the restore, it just bombs out with a
full disk, very frustrating, no easy fix (you hunt around, make space,
then try to reapply the incremental which failed.)

Another effect would be the reappearance of files you deleted for
security reasons (eg. sensitive data) after a restore, obviously this
is only worrisome to some people.

If it's a time-sharing system of course your worst problem will be
when your phone rings off the hook by users wondering why deleted
files reappeared this morning. Depending on how much you like to hear
from them from time to time this may or may not be a problem.

There are ways to avoid this using tar, nothing magic is needed, just
a shell script and some imagination (ie. put a list of directory
contents onto the tape and start by executing the deletions.)

	-Barry Shein, ||Encore||