Excessive resource usage from /usr/sbin/atd?

Question

I've been getting excessive resource usage notification from ConfigServerFirewall about this. Is it safe to disable /usr/sbin/atd, or should I just let it be and ignore it?

Solution 1

You should find out what jobs atd is running that are consuming so much time. As atd could be used to run all sorts of things, disabling it might disable all kinds of services you may need (like periodic backups or something).

Your problem may be that something is running more often than it should, or requeuing itself.

Run the command atq as superuser to see what kind of stuff is being queued.

Solution 2

Check for zero byte files in the directory where at looks for jobs. If you find any, remove them and see if the problem goes away. Story follows. (I still don't know the source of the 0 byte files, unfortunately.)

In my case, there were 2-3 empty files in /var/spool/cron/atjobs. This resulted in 200 messages per second going to rsyslogd which looked like this:

atd[3378]: File a0011601410541 is in wrong format - aborting

This was on a single board computer (think Raspberry Pi), so it drastically hurt performance of the application. atd and rsyslog were high in top output sorted by cpu.

Solution 3

To show the actual content of a particular job number on the queue, listed by atq you can use:

at -c job_num

For further suggestions see this answer.

Comments

[terdon]

That depends, do you use it? at is a way of running commands at a specified time. I use it to run commands on servers and logout, leaving the command running in the background. Find out what processes (if any) are using the at daemon (atd).

[tink]

What terdon said; you could always try to attach lsof to the PID to see what it's doing.