# Change to /var/spool/postfix/var/run/opendkim to use a Unix socket with
# postfix in a chroot:
RUNDIR=/var/spool/postfix/var/run/opendkim

[...]

# Uncomment to specify an alternate socket
SOCKET=local:$RUNDIR/opendkim.sock

[...]

USER=opendkim
GROUP=postfix
PIDFILE=$RUNDIR/$NAME.pid