[Samba] Samba permissions
Scott Mayo
sgmayo at mail.bloomfield.k12.mo.us
Fri Jul 29 16:37:52 GMT 2005
Keith Warno wrote:
> * <sgmayo at mail.bloomfield.k12.mo.us> [29/07/2005 1119EDT]:
>
>>I am working on my permissions and something does not quite make sense
>>to me. Here is what I have set.
>>
>>/DIR (Unix permissions are 3777)
>>
>>Then in samba I have the following
>>
>>[dir]
>>path = /DIR
>>read only = no
>>valid users @teach @student
>>create mask 3660
>>directory mask 3770
>>
>>Then from a windows workstation, I create a new directory inside 'dir',
>>and call it 'teach'.
>>
>>The permissions of 'teach' are 2770. It looks like it should be 3770 to
>>me since the 'directory mask' commands does a bitwise 'AND'. Anyone
>>know why this is? Maybe it is because of the DOS attributes or something.
>
>
> You're right about the bitwise AND.
>
> But default mode for a new directory is 0777. Observe:
>
> kw at pigpen[2]:~$ cd tmp
> kw at pigpen[2]:~/tmp$ umask 0
> kw at pigpen[2]:~/tmp$ umask
> 0000
> kw at pigpen[2]:~/tmp$ file foodir
> foodir: cannot open (foodir)
> kw at pigpen[2]:~/tmp$ mkdir foodir
> kw at pigpen[2]:~/tmp$ ls -ld foodir
> drwxrwxrwx 2 kw users 4096 Jul 29 11:59 foodir
>
> However, your new directory *inherited* the setgid bit (effectively a
> bitwise OR); this is simply the behavior of setgid bits on directories.
> From the man page for the stat() system call (section 2):
>
> The set GID bit (S_ISGID) has several special uses: For a
> directory it indicates that BSD semantics is to be used for
> that directory: files created there inherit their group ID from
> the directory, not from the effective gid of the creating
> process, and directories created there will also get the S_ISGID
> bit set. For a file that does not have the group execution
> bit (S_IXGRP) set, it indicates mandatory file/record locking.
>
> So, for your case:
>
> (3770 & 0777) | 2000 = 2770
>
> It is doing exactly what it should be doing. :)
>
> Keith
Ok, I guess that makes sense after you explained it. I got it to work
by using both the 'directory mask' and the 'force directory mode'. That
works but I have no idea why. I also just tried to use the 'force
directory mode' which is a bitwise 'OR' to see what I would get and here
are the permissions that I end up with in both cases. I cannot figure
out where they are coming from.
With both 'directory mask = 3770' and 'force directory mode = 3770' I get:
drwxrws--T DIR (which would be 3770)
If I just use 'force directory mode = 3770', then I get the following
permissions:
drwxrwsr-t DIR (which would be 3775)
Thanks for any help. I am glad that it works in with using both
directives, but I just want to understand why. I have been doing a lot
of reading, and just when I think that I understand how it should
work...it throws me a curve. :)
--
Scott Mayo
Technology Coordinator
Bloomfield Schools
PH: 573-568-5669
FA: 573-568-4565
Pager: 800-264-2535 X2549
Duct tape is like the force, it has a light side and a dark side and it
holds the universe together.
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