Shouldn't GNU tar be ignoring /proc with --one-file-system?

[Robert Bonomi]

> From owner-freebsd-questions at freebsd.org  Fri Nov 18 09:36:09 2011
> From: Kirk Strauser <kirk at strauser.com>
> Date: Fri, 18 Nov 2011 09:34:18 -0600
> To: FreeBSD Questions ML <freebsd-questions at freebsd.org>
> Subject: Shouldn't GNU tar be ignoring /proc with --one-file-system?
>
> I use Amanda to make nightly backups of a bunch of servers using GNU tar. Howe
> ver, gtar doesn't seem to respect its --one-file-system flag with /proc. Amand
> a runs a variation of this command:

Don't blame the software.

It is just doing *exactly* what you told it to. :)

>
>     # /usr/local/bin/gtar --create --file - --directory / --one-file-system --sparse --ignore-failed-read --totals . > /dev/null
>     /usr/local/bin/gtar: ./proc: file changed as we read it
>
> Before I file a bug report, can anyone think of a legitimate reason why gtar would be touching /proc at all?

Yup.  You (or more properly, Amanda) _told_ it to.

See the output of 'mount(8)' for the names of all the mounted filesystems on
your machine.  

*NOTE*WELL* that '/proc' is *not* a separate filesystem.  It is merely a
_directory_ with a bunch of 'special' files in it.

The 'error message' is accurate -- but it is _just_ a 'warning', and -- in *this*
circumstance -- _totally_ innocuous.

If you want to suppress generation of that error, simply add an '--exclude' for
/proc to the Amanda run.