rm lock 한(삭제) 후 다시 qmail stop, start 하면 해결된다!
# multilog: fatal: unable to lock directory /var/log/qmail/smtpd: temporary failure
multilog: fatal: unable to lock directory /var/log/qmail/smtpd: temporary failure
multilog: fatal: unable to lock directory /var/log/qmail/smtpd: temporary failure
multilog: fatal: unable to lock directory /var/log/qmail/smtpd: temporary failure