Why is this cron entry executed twice?

Question

*/5 * * * * my command 

This entry works but every 5 minutes it gets executed twice, why?

In /var/log/cron it shows:

Jun 16 22:20:01 Test CROND[12512]: (root) CMD (my command) Jun 16 22:20:01 Test CROND[12516]: (root) CMD (my command) 

So it's not from two users.

It is only entered once with crontab -e -u root. The command is a php command.

Answer 1

Nothing in the description gives reason for it to be executed twice. Look elsewhere.

• Do two users call it?
• Is it entered twice?
• Does it call itself?
• Does it set in motion conditions for repetition?

If it's a shell script you're executing, have it append whoami and date to a log file. You should be able to dig up the reason.

UPDATE

Type ps -A | grep crond, make sure crond isn't running twice.

Answer 2

The wget in crontab has often a limit of 15 minutes. In our case this was just the case, and after those 15 minutes the job ends up with a timeout and then re-runs again right away. So, the solution to this was to set up the cronjob in crontab somewhat like this :

1 2 * * * root wget --read-timeout=3600 -O - 'http://cron-job-url' >/dev/null 2>&1 

...instead of

 1 2 * * * root wget -O - 'http://cron-job-url' >/dev/null 2>&1 

So, wget is the thing. Meaning 3600 = 1 hour then. Or more if you need!