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Re: Your 2000-01-10 change CVS src/

From: Derek R. Price
Subject: Re: Your 2000-01-10 change CVS src/
Date: Fri, 19 Jan 2001 18:28:49 -0500

Autoconf folks, the comment on 'mv' in the Portable Shell section of the new
manual might not be appropriate:

     The only portable options are `-f' and `-i'.

     Moving individual files between file systems is portable (it was
     in V6), but it is not always atomic: when doing `mv new existing',
     there's a critical section where neither the old nor the new
     version of `existing' actually exists.

     Moving directories across mount points is not portable, use `cp'
     and `rm'.

Since it's not uncommon to have a build dir in /tmp, this fails on BSD with an
NFS mounted home due to /tmp's default group ownership of wheel (root) and the
default setgid behavior of its directories.  Well, it copies the file but 
error messages since root group ownership can't be set via NFS.  cp;rm should
probably be the recommended approach if the relative positioning of the files is

See the example below the following quote for the scripted version of the 

Raja R Harinath wrote:

> > Hmm.  Well, at least on my FreeBSD 4.2 system with my home directory
> > NFS mounted from Linux, I get chown errors when attempting an mv from /tmp 
> > to
> > /home, though the file does get moved.
> >
> > I seem to remember something similar on an old Sun, but that was a long time
> > ago and it may have been a directory I was trying to move.
> Hmm...
> That may be a good thing to point out to the 'autoconf' folks, to
> update their documentation about.
> If I'm not mistaken, most NFS mounts squelch root.  So, if you were
> moving a 'root' owned file from /tmp to an NFS mount on /home, the
> corresponding chown to root would fail.  This situation probably won't
> occur when building CVS, I guess.

Not owned, but the /tmp directory is using BSD's setgid mode, so the group owner
of the file is root (well, 'wheel' on my BSD, but it is gid 0):

> cd
> touch /tmp/myfile
> mv /tmp/myfile .
mv: ./myfile: set owner/group (was: 506/0): Operation not permitted
> df -k /tmp .
Filesystem    1K-blocks     Used    Avail Capacity  Mounted on
/dev/ad0s1a      168639    34584   120564    22%    /
empress:/home  18271560 10569496  6773912    61%    /home
> ls -ld /tmp
drwxrwxrwt  6 root  wheel  512 Jan 19 15:29 /tmp

I cc'd the autoconf folks, as if you hadn't noticed.  :)


Derek Price                      CVS Solutions Architect ( )
mailto:address@hidden     OpenAvenue ( )
I will not Xerox my butt.
I will not Xerox my butt.
I will not Xerox my butt...

          - Bart Simpson on chalkboard, _The Simpsons_

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