/etc/init/atd.conf is in at 3.1.13-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | # atd - deferred execution scheduler
#
# at is a standard UNIX program that runs user-specified programs at
# scheduled deferred times
description "deferred execution scheduler"
start on runlevel [2345]
stop on runlevel [!2345]
expect fork
respawn
exec atd
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