[[!meta  title="Access Control Lists"]]

On Gentoo, [[MPD]] runs as `mpd.audio`, and it creates playlists with
644 permissions (`-rw-r--r--`).  However, I wanted other members of
the audio group (i.e. me), to also have read/write permissions.  This
would allow me to sort/shuffle/create/etc. playlists from the command
line without going through MPD.

Browsing around, I ran across [Access Control Lists][ACL] ([nice
howto][howto]).  The solution is to add a default ACL to the playlist
directory:

    $ setfacl -d -m g:audio:rw- playlist
		$ getfacl --omit-header playlists
    user::rwx
    group::rwx
    other::r-x
    default:user::rwx
    default:group::rwx
    default:group:audio:rw-
    default:mask::rwx
    default:other::r-x

after which new files created in playlist will have `audio` read/write
permissions:

    $ getfacl --omit-header playlists/xyz.m3u 
    user::rw-
    group::rwx                      #effective:rw-
    group:audio:rw-
    mask::rw-
    other::r--

Several other utilities have special ACL handling (see `acl(5)`).  For
example, `ls` shows the presence of an ACL with a `+`:

    $ ls -l playlists/xyz.m3u 
    -rw-rw-r--+ 1 wking wking 0 Dec 11 17:41 playlists/xyz.m3u

[ACL]: http://en.wikipedia.org/wiki/Access_control_list
[howto]: http://wiki.kaspersandberg.com/doku.php?id=howtos:acl

[[!tag tags/linux]]