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Path: utzoo!mnetor!seismo!ll-xn!cit-vax!mangler
From: mangler@cit-vax.Caltech.Edu (System Mangler)
Newsgroups: comp.unix.wizards
Subject: Re: Backups on Live Systems
Message-ID: <2990@cit-vax.Caltech.Edu>
Date: Mon, 8-Jun-87 22:28:00 EDT
Article-I.D.: cit-vax.2990
Posted: Mon Jun  8 22:28:00 1987
Date-Received: Thu, 11-Jun-87 06:01:24 EDT
References: <132@dvm.UUCP> <725@aramis.rutgers.edu> <20070@sun.uucp> <6279@pur-ee.UUCP>
Organization: California Institute of Technology
Lines: 25
Summary: ignoring modified files is not the answer

In article <6279@pur-ee.UUCP>, davy@pur-ee.UUCP (Dave Curry) writes:
> Basically, these mods
> tell dump to ignore any inode which has changed since the dump started.
> This has the minor disadvantage that some files (those being modified)
> will be missing from the dump

For instance, /dev/rmt8, /dev/console, and /usr/adm/acct will be missing,
even on a full dump done in single-user mode.

This seems very much like closing the barn door after the horse
has run away.  It doesn't hurt for the file to be modified while
dump isn't looking (so long as it stays the same type); what hurts
is when the file is modified in the middle of being dumped, something
you don't detect and can't do anything about even if you detected it
(other than warn the operator to start over).  It is a problem common
to dump, tar, cpio and probably others, because they all assume that
st_sizes won't change while the file is being written to tape.

You do, at least, protect against regular inodes becoming directories
or vice-versa.	However, 4.3bsd dump already does that.  I fail to
see what you've gained.

(Didn't we say all these things last year?)

Don Speck   speck@vlsi.caltech.edu  {seismo,rutgers,ames}!cit-vax!speck