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From: mangler@cit-vax.UUCP
Newsgroups: comp.unix.questions
Subject: Re: File system problems
Message-ID: <3430@cit-vax.Caltech.Edu>
Date: Sat, 1-Aug-87 04:34:44 EDT
Article-I.D.: cit-vax.3430
Posted: Sat Aug  1 04:34:44 1987
Date-Received: Sun, 2-Aug-87 10:34:46 EDT
References: <8467@brl-adm.ARPA> <1052@mind.UUCP> <4221@teddy.UUCP>
Organization: California Institute of Technology
Lines: 31
Summary: level zero dump after full restore

>In article <8467@brl-adm.ARPA> KFL@AI.AI.MIT.EDU (Keith F. Lynch) writes:
>>He has also said that after using doing a restore of a zero level dump,
>>it is necessary to immediately do another zero level dump

In article <4221@teddy.UUCP>, jpn@teddy.UUCP (John P. Nelson) writes:
> not doing another level 0 dump [...] COULD render
> all subsequent incremental backups useless.  To quote from the "restore"
> manual page:
>      [...]  Thus, a
>      full dump must be done to  get  a  new  set  of	directories
>      reflecting the new file positions, so that later incremental
>      dumps will be correct.

[BSD-specific discussion]

Could someone explain to me why this should be true?  After a full
restore, the st_ctime of every file/directory has been updated, so the
next dump, no matter what level, should dump every single file, right?
How is running restore on a fresh filesystem different from cleaning
off the current filesystem with "rm -rf" and creating a bunch of files?

Admittedly, since the incremental will be just as large as a full, you
might as well do a full, but it seems like something is basically wrong
if an incremental doesn't work just because you changed *everything*.
[Yes, I know that restore bombs if you changed *nothing*, but so what].

Perhaps the comments in the man page are a holdover from 4.1bsd dump,
which did, in fact, need this restriction because restor [sic] wrote
the raw disk and thus did not update st_ctime?

Don Speck   speck@vlsi.caltech.edu  {ll-xn,rutgers,amdahl}!cit-vax!speck