linuxexpert-practice-labs/labs/ubuntu-desktop/5-3-acls

Ubuntu Desktop 5.3: ACLs

Giving one extra user and one group access to a shared folder with ACLs, default ACLs for new files, and copying a file with its ACL.

Before you start

The lab creates users alice and bob (password Lab-Pass-1) and group designers, with bob in it, as the chapter does. It installs the acl tools (getfacl, setfacl) if they're missing. /srv/shared doesn't exist yet.

Tasks

1. Create /srv/shared, owned by you (your login user, or root) with mode 750, where alice can list and read files and the group designers can also create them.
2. Make every file created in /srv/shared from now on readable and writable by designers and readable by alice.
3. As bob, create /srv/shared/new. Then copy it to /tmp so that its ACL comes along (it belongs to bob, so use sudo). Ubuntu empties /tmp at every boot, so do this task last and check it before you reboot.

Hints

• setfacl -m u:alice:rx,g:designers:rwx; getfacl -c shows the entries and the mask. sudo -u bob touch /srv/shared/t should work and sudo -u alice touch /srv/shared/t2 should be denied.
• Default entries: setfacl -d -m .... Test with sudo -u bob touch /srv/shared/new and getfacl -c /srv/shared/new (look at #effective:).
• cp -a, or cp --preserve=all; ls -l shows a + after the permissions of a file with an ACL.