Re: Sharing a directory

[Martin OConnor <martinoc@gmail.com>]

On Sun, 2006-01-29 at 01:03 +0000, Magnus Therning wrote:
> On Sun, Jan 29, 2006 at 11:10:33AM +1100, Jonathan Wheelhouse wrote:
> >
> >Got a question re UNIX permissions: I've got a directory, photos, in my
> >home directory, that I want the wife and kids to put digital photos.
> >
> >I created a group, photo, and put them all in it.  I changed the group
> >on the directory to be photo.  I set the sgid bit on the directory so
> >that files created in the directory will have that group.  I set the
> >restricted deletion flag on the directory so that people can only
> >delete their own files not those of others.
> >
> >Now the problem is that if people create sub-directories in this
> >directory and then populate that sub-directory with photos only they
> >have access to those photos.  How can I make it so that even if they
> >create sub-directories the files in the sub-directory have their group
> >set to photo?
> 
> I'm not sure I understand you, I was under the impression that subdirs
> created under a dir with sgid bit set would inherit the group with the
> sgid bit set:
> 
>  % mkdir test
>  drwxr-xr-x 3 magnus magnus 4096 2006-01-29 00:58 test
>  % sudo chgrp users test
>  % sudo chmod g+s test
>  % ls -ld test
>  drwxr-sr-x 3 magnus users 4096 2006-01-29 00:58 test
>  % cd test
>  % touch hello
>  % mkdir dir
>  % ls -l
>  drwxr-sr-x 2 magnus users 4096 2006-01-29 00:58 dir
>  -rw-r--r-- 1 magnus users    0 2006-01-29 00:58 hello
> 
> Anything more complicated you might need can probably be solved using
> ACLs (e.g. if users use different umasks).
> 
> /M
> 
You can use umask to change your users default file permissions. 
If you put: umask 0022 
in the .bashrc and .bash_profile, any new files and dirs will be group
writable by default.
The only problem with this is that it applies to *ALL* files that user
creates, not just the files in the sgid directory.
Hope this helps,

Thanks,
Martin OConnor