Do ACLs always override default chmod permissions?

Question

What if I have a file on a Linux machine with user permissions of rw but assigned that user rwx permissions via ACL?

Will the ACL override that default user permissions and allow execute access?

nick@nick-XPS-9315:~$ cd /tmp
nick@nick-XPS-9315:/tmp$ touch test
nick@nick-XPS-9315:/tmp$ ll test
-rw-rw-r-- 1 nick nick 1210 Aug 11 09:37 test
nick@nick-XPS-9315:/tmp$ setfacl -m u:nick:rwx ./test
nick@nick-XPS-9315:/tmp$ ll test
-rw-rwxr--+ 1 nick nick 1210 Aug 11 09:37 test*
nick@nick-XPS-9315:/tmp$ getfacl test
# file: test
# owner: nick
# group: nick
user::rw-
user:nick:rwx
group::rw-
mask::rwx
other::r--

Have you tried it by giving account foo the permissions you're suggesting? — doneal24, Aug 11 '23 at 15:57
I found the answer, there's a hierarchy or permissions I posted below, it's not as simple as ACL vs chmod. — Nick Kiermaier, Aug 11 '23 at 16:00
Does this answer your question? Precedence of user and group owner in file permissions. Check the accepted answer it goes into detail about what happens with ACLs. — Eduardo Trápani, Aug 11 '23 at 16:30

Nick Kiermaier · Answer 1 · 2023-08-12T12:17:44.053

-1

I found a permissions hierarchy.

System immediately stops when finds a match at any step and does not proceed further.

Is user owner? uses the user owner chmod permissions
Any user ACLs? Unions ACL permissions and uses those ACL permissions
Is group owner? uses the group owner chmod permissions
Any group ACL's? Unions those ACL group permissions and uses those ACL permissions
Get permissions of others entity

edited Aug 12 '23 at 12:17

answered Aug 11 '23 at 15:59

Nick Kiermaier

1

That's a good summary but is missing the covering of the ACL mask. – Stéphane Chazelas Aug 11 '23 at 17:27
I can add that, where would that go? Doesn't that apply to the default at file creation? – Nick Kiermaier Aug 12 '23 at 12:16
The ACL mask further restricts the rights obtained in points 2, 3 and 4 above. See man 5 acl for details. – Stéphane Chazelas Aug 12 '23 at 13:15

Do ACLs always override default chmod permissions?

1 Answers1