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

From: Raja R Harinath
Subject: Re: Your 2000-01-10 change CVS src/
Date: 19 Jan 2001 18:19:25 -0600
User-agent: Gnus/5.090001 (Oort Gnus v0.01) Emacs/21.0.95

"Derek R. Price" <address@hidden> writes:
> Autoconf folks, the comment on 'mv' in the Portable Shell section of the new
> manual might not be appropriate:
>   `mv'
>      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 outputs 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 unknown.
> 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

There's no 'setgid' bit on the /tmp directory.  Does BSD still exhibit
'setgid' behaviour?  I don't thing the sticky tag changes 'setgid'
behaviour of a directory.

  * What are the permissions on /tmp/myfile?
  * Can you create files in the your home directory?
  * Are you in, or did you change with newgrp(1) to, group 'wheel'?

Still, I'm starting to agree with you that cp/rm makes more sense than
mv to move files across mount points, what with the way file ownership
and NFS interact.

- Hari
Raja R Harinath ------------------------------ address@hidden
"When all else fails, read the instructions."      -- Cahn's Axiom
"Our policy is, when in doubt, do the right thing."   -- Roy L Ash

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