Edit: /usr/lib/tmpfiles.d/at.conf (223B)
# at - Tmpfiles configuration for at daemon
# Create /var/spool/at directory structure for the at daemon
d /var/spool/at 0700 root root - -
d /var/spool/at/spool 0700 root root - -
f /var/spool/at/.SEQ 0600 root root - -