chmod says operation not permitted

lewyx · 10-12-2009, 08:59 AM

I have 2 users (a and b) in the users group. The directory "test" and the file "test/example.zip" both have permissions 777 and are owned by a/users.
The other user (b) tries chmod 666 example.zip and gets the error "operation not permitted", though he also has all rights through users (it is the only group a and b belong to).
Why is chmod not permitted for b? Where in the hell can I find documentation about what rights one has to hold to change permissions on an object (odd that man chmod does not mention that)?

~sHyLoCk~ · 10-12-2009, 09:02 AM

Run it as root or use sudo chmod

zhjim · 10-12-2009, 09:03 AM

chmod is only usable by the root user or the owner of the file itself.
chown is only usable by the user root. Reason for this is that you could just create a file, put the suid bit onto it and chown it to root and voila root access is yours.
Also when quotas are in use. If I was about to exced my quota I just give my bigest file to you and live happily after...

lewyx · 10-12-2009, 09:22 AM

Quote:

Originally Posted by zhjim

chmod is only usable by the root user or the owner of the file itself.
chown is only usable by the user root. Reason for this is that you could just create a file, put the suid bit onto it and chown it to root and voila root access is yours.
Also when quotas are in use. If I was about to exced my quota I just give my bigest file to you and live happily after...

The reasons for chown are straightforward.
The limitation for chmod I do not understand. How can I make a group of people manage their own things?! Can I not achieve that anyone who can write a directory may change the files metadata (like rights) within?

Currently the users in "users" have to maintain the directory (and its subtree) "test", they _all_ need to be able to change the contents and adjust permission, but they must not be granted any other privileges (especially not any root permissions).

zhjim · 10-12-2009, 10:53 AM

As long as users are all in the same group you can work with umask to make sure everybody has the right to write to it. Also the suid group bit might be to some help. When set to a dir every file underneith it while be created with the group.
Or check out on ACL's. They give you finer control of access rights. But I dunno if you'll be able to allow things like chmod.

Maybe if you supply some use cases we'll find something suitable?

onebuck · 10-12-2009, 11:00 AM

Hi,

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