Crontab repeats itself


#1

I’m having a strange experience running a very simple command with crontab. Here is the entry:

5,25,45 * * * * /usr/bin/uptime >> /home/user/mydomain.com/cpuload.txt

So basically, it dumps the output of uptime every 20 minutes. However, in cpuload.txt, I get this:

02:05:01 up 2 days, 12:06, 3 users, load average: 0.96, 0.74, 0.57
02:05:03 up 2 days, 12:06, 3 users, load average: 0.96, 0.74, 0.57
02:05:59 up 2 days, 12:07, 3 users, load average: 0.62, 0.68, 0.56
02:25:01 up 2 days, 12:26, 3 users, load average: 0.35, 0.38, 0.40
02:45:01 up 2 days, 12:46, 3 users, load average: 1.00, 0.73, 0.59
03:05:00 up 2 days, 13:06, 3 users, load average: 0.32, 0.49, 0.59
03:25:01 up 2 days, 13:26, 2 users, load average: 1.09, 0.82, 0.88
03:26:01 up 2 days, 13:27, 2 users, load average: 0.67, 0.75, 0.85
03:45:01 up 2 days, 13:46, 2 users, load average: 0.47, 0.57, 0.65

Notice the command was executed three times at the top, and twice at 13:25. Any ideas why it’s doing this? I tried putting the command into a .sh file to no avail.

Any input appreciated, thank you.


#2

Your cron entry looks fine and running the command alone works fine for me. I added the entry to mine to see if anything funky happens for me (my other entries are once-a-day and haven’t had problems). What machine are you on?

Check out Gordaen’s Knowledge, the blog, and the MR2 page.


#3

Try replacing /usr/bin/uptime with /usr/bin/w and see if you get the same results. You may get some additional text thrown in but see if you get the triplicates. Try running /usr/bin/uptime from the command line to check for any hard soft links.


Norm

Opinions are my own views, not DreamHosts’.
I am NOT a DreamHost employee OK!! :@

You act on my advice at your own risk!


#4

Mine doubles up (and even triples) fairly often too (21 entries when there should have been 13). I’ll try Norm’s suggestion and maybe that will tell us if it is a cron problem or not.

Check out Gordaen’s Knowledge, the blog, and the MR2 page.


#5

Thanks for your replies. Good to hear someone else experiencing this. :slight_smile: I’ll try /usr/bin/w now.

I am on plenty.dreamhost.com.


#6

Same thing happens to me with either command. I’m on rollo.

Check out Gordaen’s Knowledge, the blog, and the MR2 page.


#7

Same here. This is really bizarre. crontab doesn’t run all commands multiple times, right?

Could a DH employee shed some light on this? I don’t want to submit a ticket, as it’s probably not warranted nor terribly urgent.


#8

I’ve had daily cron jobs run regularly for quite a while without ever having it trigger multiple times like this, but I’ve never run anything more common than daily, so I have no idea shrug You could submit it with low priority, I suppose.

Check out Gordaen’s Knowledge, the blog, and the MR2 page.


#9

Just tried the same crontab as yourself and it seems to be okay:-

03:25:00 up 3 days, 13:26, 6 users, load average: 1.09, 2.03, 2.23
03:45:03 up 3 days, 13:46, 5 users, load average: 2.79, 2.46, 2.45
04:05:02 up 3 days, 14:06, 5 users, load average: 3.90, 3.86, 3.10

as does uptime without a path (using different time periods):-

03:26:02 up 3 days, 13:27, 6 users, load average: 1.58, 2.03, 2.22
03:46:03 up 3 days, 13:47, 5 users, load average: 1.69, 2.22, 2.36
04:06:02 up 3 days, 14:07, 5 users, load average: 3.58, 3.87, 3.15

I would not think it a server issue.
Do make sure that you have a blank line at the end of your crontab line to stop it looping. i.e. press enter once or twice before you save the crontab.


Norm

Opinions are my own views, not DreamHosts’.
I am NOT a DreamHost employee OK!! :@

You act on my advice at your own risk!


#10

My cron job is repeating too. Sometimes at the same moment. Sometimes a minute later.

Did anyone find a solution to this?

Terry


#11

Maybe this problem is related to the unstable system clock:

http://discussion.dreamhost.com/showflat.pl?Board=forum_programming&Number=60556

Terry