Well, groups are used to allow a number of people to use something rather
than just letting the owner use it. For instance, the permissions on my
volume program look like this...
-rwxr-x--- 1 root sound volume ....
this means that the group 'sound' has read and execute permission to it,
and the owner, root, has read, write, and execute permission to it. That
way nobody can change the volume of my sound card except the users in
group sound. This was accomplished with a chmod command (chmod 750
/sbin/volume). Now, as for your backup group. I suppose that you could
give read access to your hard drive partition(s). My root is /dev/sda1.
ther permissions are 'rw-rw---- root disk'. Ok, the reason that all other
users don't have access to this file is, well, you could conceiveably read
the raw hard drive data and get things like shadow passwords and the like.
Regular users don't need read\write access to a raw disk. Now, add your
user, backup, to the group disk. Then backup will have read access to the
disk. Also make sure the permissions are the same to your backup device
be it a tape or a removable hard disk. Then, from user backup your could
use dump (I think this might not let a non-root user run it) or tar to
backup the file system. Something like 'dump 0uf /dev/tape /dev/sda1' or
something of the like.
-CJO-
C.J. Oster (Linux Guru/Surge Addict)
P.O. Box 132
Ponca City, OK
74602-0132
----------------------------------------------------------------
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CONTROLED MUNITIONS.
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On Thu, 28 May 1998, Joseph Martin wrote:
> I am having trouble understanding aspects of file/directory permissions. I
> know how to make file readable, writeable, etc., but am having trouble
> with advanced aspects. For instance I once read that you can create a user
> called backup and use it to backup the whole disk. The idea was to give
> backup read-only access to the whole disk. How can you give a specific
> user certain permissions on files? What exactly are groups used for?
>
> Thanks,
>
> Joseph Martin
> [EMAIL PROTECTED]
> Linux newbie/sysadmin ( dangerous combo! ;-> )
>
>
