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From: dillon@flea.best.net (Matt Dillon)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: dump: interactions with other processes
Date: 15 Jan 1997 23:51:00 -0800
Organization: BEST Internet Communications, Inc.
Lines: 34
Message-ID: <5bkml4$e28@flea.best.net>
References: <32DADE85.1153@cpmx.saic.com>
NNTP-Posting-Host: flea.best.net
Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:34110
:In article <32DADE85.1153@cpmx.saic.com>,
:Cameron H. Matthews <cameron.h.matthews@cpmx.saic.com> wrote:
:>Hi,
:> Anyone have any idea what happens if dump encounters a file with an
:>exclusive lock on it? What about a file that is simply open for write?
:>What happens if dump is dumping a file when another process tries to
:>remove
:>the file?
:> Any information, anecdotal or otherwise, would be greatly appreciated.
:>
:>Thanks,
:>
:>Cameron
:>--
:>Cameron H. Matthews
:>Science Applications International Corporation
:>mailto:cameron.h.matthews@cpmx.saic.com
:>foneto:(619)535-7161
dump does not work on the filesystem level, but instead with the
block device so it has *no* notion of any advisory locks or open
descriptors. If you remove or modify a file out from under dump,
then the dumped file may wind up corrupt. If you create a file
in a directory that is currently being dumped, the dump of the
directory may wind up incomplete or corrupt.
I seem to recall that dump tries to check for such modifications,
but it will not catch every case. Basically, it is best to dump
only idle filesystems. Many people dump live filesystems, and
this generally works out ok if you use the correct dump regimen
(modified tower of hanoi, as per the manual page).
-Matt