topic Re: File mode in Operating System - Linux

File mode

peterchu — Fri, 13 Feb 2004 03:11:06 GMT

I have a file on the system , many users can access and update it , how can I fix the file mode ( eg. 666 ) , to prevent the user change the mode ? thx.

Re: File mode

Elmar P. Kolkman — Fri, 13 Feb 2004 03:18:09 GMT

This can be done by closing the directory for writing... Just do: 'chmod go-w .' while in the directory. This means they can't create files too, btw.

Another way: set the 'sticky' bit on the directory: 'chmod o+s .' This has some other side effects (users can't remove files not owned by them.

Test to see what's best for your situation.

Re: File mode

K.C. Chan — Fri, 13 Feb 2004 09:48:05 GMT

just make sure the file is not own by any users which you do not want to have ownership; maybe you want to own the file. AFAIK, you can only change mod if you own the file (besides all mighty powerfull root, offcourse).

Re: File mode

Martin P.J. Zinser — Fri, 13 Feb 2004 14:48:16 GMT

Hello Peter,

exactly which mode to set really depends on how this file is supposed to be used. Do all users on the system need rw to the fil? In that case 666 is the right protection. Do only users of one group need access? Chmod 660 would do that.
Ist is it a few users from different groups, add a new group, add the members to it, make the file owned by the group and again go 660. Users might need to do a chgrp to the right group in this case to gain access. If you need finegrained access have a look at ACLs.

Greetings, Martin