slapd with back_sock does not create a socket

Solution 1:

The purpose of back_sock is to connect to an another socket that already exists. It's documented in the slapd-sock(5) manpage. It certainly does not create any socket.

If you review your logs, you'll only see errors when an action is attempted, because the sock backend opens the socket each time it needs to do some action, and closes it afterwards. You'll see an entry could not open socket in your logs if the socket cannot be opened for each action.

If you're trying to make slapd listen on a socket instead, you need to modify /etc/default/slapd, and adjust/add the slapi:// URL (remember you'll need to encode slashes as %2f, see slapd(8) for more details).