Setting access privileges

| Theoretical Chemistry Home Page > Documentation

If you want to make a file accessible for others use:

   chmod o+r <file name>

('o' stands for others). Only we have access to our computer system and 'others' means 'other members of our group'.

On request, a special group theochem has been created which includes all the group members; this allows to revoke access for - non-existing currently - users of our system, that do not belong to theoretical chemistry. The method is then two-step:

   chmod g=r <filename>; chgrp theochem <filename>

User Private Group Rationale - from Redhat Manual

Although UPG is not new to Red Hat Linux 6.0, many people still have questions about it, such as why UPG is necessary. The following is the rationale for the scheme.

You'd like to have a group of people work on a set of files in say, the
/usr/lib/emacs/site-lisp directory. You trust a few people to mess around in there, but certainly not everyone.
So you enter:
```
chown -R root.emacs /usr/lib/emacs/site-lisp
```
and you add the proper users to the group.
To allow the users to actually create files in the directory you enter:
```
chmod 775 /usr/lib/emacs/site-lisp
```
But when a user creates a new file it is assigned the group of the user's default group (usually users). To prevent this you enter
```
chmod 2775 /usr/lib/emacs/site-lisp
```
which causes everything in the directory to be created with the ``emacs'' group.
But the new file needs to be mode 664 for another user in the emacs group to be able to edit it. To do this you make the default umask 002.
Well, this all works fine, except that if your default group is ``users,'' every file you create in your home directory will be writable by everybody in ``users'' (usually everyone).
To fix this, you make each user have a ``private group'' as their default group.

At this point, by making the default umask 002 and giving everyone a private default group, you can easily set up groups that users can take advantage of without doing any magic. Just create the group, add the users, and do the above chown and chmod on the group's directories.

Setting access privileges

User Private Group Rationale - from Redhat Manual

Links