Linux - group member cannot delete file with rw permission

Question

Below shows a file, /tmp/testfile, owned by user1 with group changed to wheel that also includes user2. The file has rw permission for the group. So shouldn't any member of the group be able to delete it? The example output below shows that user2 is not able to delete the file. Why?

[user2@files ~]$ ls -l /tmp/testfile
-rw-rw-r-- 1 user1 wheel 0 Jul 18 18:54 /tmp/testfile
[user2@files ~]$ groups
user2 wheel
[user2@files ~]$  rm /tmp/testfile
rm: cannot remove `/tmp/testfile': Operation not permitted

possible duplicate of [Why can't I delete a file where I have group write permissions on?](http://superuser.com/questions/373115/why-cant-i-delete-a-file-where-i-have-group-write-permissions-on) — Hastur, Jul 18 '14 at 22:52
Furthermore to the complete explanation by @grawity, a good solution is to create your 'own' directory under `tmp` and fix the sticky situation — fcm, Oct 12 '17 at 17:28

score 35 · Accepted Answer · edited Jul 19 '14 at 14:38

35

First, you're looking at the wrong permissions. When you move/rename/delete a file, you're only modifying the parent directory – the file's own permissions are not checked. You only remove an entry from the directory's list of files. Therefore you should check the permissions of the parent directory (in this case /tmp).

$ ls -ld /tmp
drwxrwxrwt 15 root root 460 Jul 19 15:18 /tmp/

Second, /tmp is special. On practically all systems, it's writable by anyone (ugo=rwx), so at first glance, it looks like anyone could rename or delete any file in it. This would of course make it easy (well, even easier) to create problems for other users, therefore /tmp always has the "sticky" aka "restricted deletion" mode set (o+t). With this mode set, only the file's owner can move or delete files in that directory, regardless of any permissions.

(On GNU coreutils, the chmod(1) manual page has a section about the "restricted deletion flag or sticky bit".)

edited Jul 19 '14 at 14:38

Cristian Ciupitu

5,513
2
37
47

answered Jul 18 '14 at 19:25

u1686_grawity

426,297
64
894
966

I'm facing the same issue due to second point of special sticky permission. I tried to remove it `chmod o-t /tmp` and then re-tried to delete the file, but it is still complaining the same. – Shashank Agrawal Mar 23 '15 at 11:43
2

Not only the file owner can delete files under said directory, but also root and the owner of the directory (e.g. /tmp). – wulfgarpro Dec 09 '15 at 22:13
About `o+t` - `o` is for _others_, but What does `t` mean? - I always have read about r/w/x – Manuel Jordan Sep 22 '21 at 13:40
`t` means "sticky". It says so in the post... – u1686_grawity Sep 22 '21 at 13:51
@user1686 About the "parent directory" - Does it only apply to the immediate parent directory, right? – Manuel Jordan Oct 05 '21 at 02:08

Linux - group member cannot delete file with rw permission

1 Answers1

Linked