qmail-newu reads the assignments in
/var/qmail/users/assign and writes them into
/var/qmail/users/cdb in a binary format suited
for quick access by
If there is a problem with
qmail-newu complains and leaves
qmail-newu ensures that
users/cdb is updated atomically,
qmail-lspawn never has to wait for
qmail-newu to finish.
qmail-newu makes no attempt to protect against two simultaneous updates of
users/cdb format is portable across machines.