Questions tagged [cron]

Cron is a time-based job scheduler in Unix-like computer operating systems. Cron enables users to schedule jobs (commands or shell scripts) to run periodically at certain times or dates.

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7 answers
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Why is my crontab not working, and how can I troubleshoot it?

This is a Canonical Question about using cron & crontab. You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is ...
Eric Leschinski's user avatar
128 votes
11 answers
91k views

Prevent duplicate cron jobs running

I have scheduled a cron job to run every minute but sometimes the script takes more than a minute to finish and I don't want the jobs to start "stacking up" over each other. I guess this is a ...
Tom's user avatar
  • 4,367
47 votes
13 answers
72k views

How to change "From:" field for emails from Cron?

I use remote SMTP via nullmailer and it requires set From field to the specific name, but cron set it as [email protected]. How could I change it to something like [email protected]?
Alexander Artemenko's user avatar
15 votes
4 answers
1k views

How to schedule server jobs more intelligently than with cron?

I run a job every minute to reindex my site's content. Today, the search engine died, and when I logged in there were hundreds of orphan processes that had been started by cron. Is there another ...
John's user avatar
  • 153
106 votes
2 answers
48k views

escaping double quotes and percent signs (%) in cron

The following command works from prompt but not from crontab. grep abc /var/log/messages | grep "`date '+%B %d'`" | mail -s"abc log of `hostname`" s.o+`hostname`@gmail.com I need ...
shantanuo's user avatar
  • 3,619
26 votes
2 answers
7k views

Weird syslog order

Have you ever seen wrong order in /var/log/syslog ? I think that it causes only crontab. Jun 28 22:20:01 alex CRON[2327]: (root) CMD (something > /dev/null) Jun 28 22:21:01 alex CRON[2700]: (root) ...
Tomasz's user avatar
  • 371
163 votes
12 answers
332k views

Best practices for setting a cron job for Let's Encrypt (Certbot) renewal?

Is this correct way to set cron for renewal of Let's Encrypt cert in Apache2 ? I use Ubuntu 16.04. @monthly letsencrypt renew && service apache2 reload
user3448600's user avatar
  • 1,629
12 votes
4 answers
7k views

Crontab running before nfs mounted

Running Cronjob @reboot returns that file on nfs share does not exist. Example @reboot python /abs/path/to/script.py mail from crontab on startup reads "more or less" /usr/bin/python can't open ...
Rusty Weber's user avatar
70 votes
3 answers
57k views

Better logging for cronjobs? Send cron output to syslog?

I am looking for a better way to log cronjobs. Most cronjobs tend to spam email or the console, get ignored, or create yet another logfile. In this case, I have a Nagios NSCA script which sends data ...
Stefan Lasiewski's user avatar
65 votes
10 answers
74k views

Can I run a cron job more frequently than every minute?

Is it possible to run a cron job every 30 seconds without a sleep command?
user15336's user avatar
  • 803
8 votes
2 answers
6k views

My cron tasks report command not found [duplicate]

This is the contents of my crontab file: 0 0,6,12,18 * * * cd /var/www/app/current && backup perform --trigger db_backup --config_file config/backup.rb --data-path db --log-path log --tmp-...
DEfusion's user avatar
  • 287
56 votes
6 answers
74k views

Cron: Only get errors in emails?

I finally set up a realistic backup schedule on my data through a shell script, which are handled by cron on tight intervals. Unfortunately, I keep getting empty emails each time the CRON has been ...
Industrial's user avatar
  • 1,599
15 votes
3 answers
31k views

How can I test a new cron script?

I'm running on a couple of different Linux distros (Fedora 11, CentOS 5 and SuSE 10.2) and often run into a problem where a new script that I want to run as a cron job works fine when called direct ...
gareth_bowles's user avatar
8 votes
4 answers
4k views

How to customise email headers from Vixie-cron (debian) and msmtp?

I have had some trouble with getting cron to send emails. My ISP requires that the "From:" field match the email address the email is being sent from, otherwise the email is rejected. As cron ...
robin's user avatar
  • 281
7 votes
2 answers
5k views

Timezone for cron jobs

We have a VDS running CentOS 5.5 that was created and configured with the EDT timezone. I have replaced etc/localtime with a link pointing to the Australia/Melbourne (UTC+10) timezone file. Running ...
John Gardeniers's user avatar
3 votes
5 answers
6k views

Difference of running scripts manually or with a cronjob

I have a PHP script that I want to run every 10 minutes, going through database records and creating/editing movies through MEncoder. I've set up cron job to accomplish this, but it doesn't work very ...
Björn's user avatar
  • 135
2 votes
8 answers
2k views

How to run a cron job?

I have a sample perl script which i need to run using cron daily ,could any one let me know the exact syntax to use cron job. Thanks in advance.
user avatar
166 votes
14 answers
561k views

Running a cron job manually and immediately

(I have already read How can I test a new cron script ?.) I have a specific problem (cron job doesn't appear to run, or run properly), but the issue is general: I'd like to debug scripts that are ...
Pistos's user avatar
  • 3,153
83 votes
3 answers
152k views

What does * * * * * (five asterisks) in a cron file mean? [duplicate]

The first noncomment line in a legacy crontab file begins with five asterisks: * * * * * ([a_command]) >/dev/null 2>&1 The authors are gone, so I do not know their intent. What does all-...
Thomas L Holaday's user avatar
61 votes
6 answers
36k views

How to Modify a Cronjob Email Subject

I am running a half dozen different cron jobs from my hosting at Hostmonster.com. When a cronjob has been executed I receive an email with the output of the script. The email comes in the format of: ...
justinl's user avatar
  • 733
43 votes
6 answers
50k views

How can I prevent cron from filling up my syslog?

I have a script which needs to be executed each minute. The problem is that cron is logging to /var/log/syslog each time it executes. I end up seeing something like this repeated over and over in /...
user7321's user avatar
  • 1,026
25 votes
7 answers
24k views

How to use my aliases in my crontab?

I have some commands in my .profile that I want to invoke from my crontab. For example, if I have, alias notify-me="~/bin/notify.pl -u user1" alias notify-team="~/bin/notify.pl -u user1 user2 ...
Keith Bentrup's user avatar
19 votes
5 answers
16k views

Why is only one wget command working in my crontab?

I wish to fetch content from a PHP script on my server two times a day, altering a query variable lang to set what language we want, and save this content in two language specific files. This is my ...
Alexander Wallin's user avatar
13 votes
2 answers
959 views

How does cron handle remainders in "every so often" jobs

If I do this: */9 * * * * /path/to/wotnot At what times will the task run in two hours, starting at 09h00 Is it A: 09h00 09h09 09h18 09h27 09h36 09h45 09h54 10h03 10h12 10h21 10h30 10h39 10h48 ...
Jesse's user avatar
  • 243
12 votes
2 answers
55k views

Cronjob run every two weeks, on Saturday, starting on this saturday

Today is Friday, October 3, 2014 3:58 AM I want to schedule a cronjob like that to run it at the following dates: Saturday, October 4, 2014 8:00 AM Saturday, October 18, 2014 8:00 AM Saturday, ...
kupa's user avatar
  • 381
8 votes
3 answers
10k views

Expired "authentication token" for user with deleted password

The Setup: 1) The user's password was deleted with "passwd -d " command 2) The user has cron jobs running The Problem: Once every 30 days (default password expiration policy) the cron fails with an ...
Aleksey Sanin's user avatar
5 votes
1 answer
12k views

logrotate cron job not rotating certain logs

I added two scripts in "logrotate.d" directory for my application logs to be rotated. This is the config for one of them: <myLogFilePath> { compress copytruncate delaycompress dateext ...
user2206396's user avatar
5 votes
5 answers
5k views

What's the best way of setting up a cron job to check that a long-running process is still going and if not, start it?

As per the title: What's the best way of setting up a cron job to check that a long-running process is still going and if not, start it? If I start a long-running process in cron, is it going to ...
Ben's user avatar
  • 405
5 votes
2 answers
5k views

How do I set a time zone for a crontab?

I would like to use UTC for the scheduling times in a crontab for a single user, regardless of the current time zone of the server. How do I do this on Debian Etch?
Christian Studer's user avatar
4 votes
2 answers
4k views

Multiple instances of CRON_TZ inside a cron file (CentOS)

Is it possible to have multiple timezones in the /etc/crontab file, like below? CRON_TZ=Europe/Paris */20 * * * * root /home/user/script.sh >/dev/null 2>&1 */5 * * * * root /home/...
Nikk's user avatar
  • 239
2 votes
2 answers
4k views

executing a sh script from the cron

I have a test.sh script #!/bin/sh php /home/v/file.php sh /root/x/some.sh when I execute the file as root from command line it works. sh /home/v/test.sh when I set it to crontab -e (is the root ...
Elzo Valugi's user avatar
2 votes
9 answers
12k views

CronTab: Not running my PHP scripts?

final edit: i have moved this to 406 Error with GET Cron Job? EDIT 4: i am getting a 406 error page with this cron! here is the crontab (copied from cPanel): * * * * * GET https://abc.com/cron/...
Garrett's user avatar
  • 203
2 votes
1 answer
3k views

Cron jobs not working anymore

Cron jobs were working for months in the past but recently I had a high server load and now cron jobs aren't executing my php files (the same ones that were working before). When I check the cron log ...
user3186337's user avatar
1 vote
3 answers
27k views

crontab to run bash script (ssh command in it) not working

CentOS 5.4 (in my script file - script.sh) #!/bin/bash ssh 192.168.0.1 'iptables -L' > /tmp; (in /etc/crontab) 30 21 30 9 * root /bin/bash /script.sh If I run the script in terminal, things ...
Stan's user avatar
  • 1,397
0 votes
1 answer
2k views

No log handling enabled - turning on stderr logging Cannot find

I'm trying to setup a Cron Job that runs a .php file that will automate client email correspondance. I've created the .php file and the Cron Job through cPanel. Everything works fine in that I'm ...
Deano's user avatar
  • 11
-2 votes
1 answer
340 views

shell script doesn't run correctly in cron [closed]

I want to call a shell script I wrote from a cron. The shell script uses the program Linkchecker. If I run the shell script from the terminal it works just fine. However, when cron runs I get the ...
rich's user avatar
  • 1
255 votes
10 answers
327k views

When does `cron.daily` run?

When do entries in cron.daily (and .weekly and .hourly) run, and is it configurable? I haven't found a definitive answer to this, and am hoping there is one. I'm running RHEL5 and CentOS 4, but for ...
warren's user avatar
  • 18.7k
150 votes
5 answers
94k views

Job scheduling using crontab, what will happen when computer is shutdown during that time?

I schedule some tasks using crontab. What will happen if my computer is shutdown or turned off during the time when cron was scheduled to do something? Does each missed cron job run after computer ...
seg.server.fault's user avatar
101 votes
10 answers
251k views

How to disable everything in crontab -l?

I just want to pause everything. Don't execute anything listed on crontab -l.
Alex's user avatar
  • 8,591
74 votes
5 answers
136k views

How can I monitor what logrotate is doing?

How can I monitor what logrotate is doing in Ubuntu? Can the activity of logrotate be monitored?
user avatar
73 votes
6 answers
166k views

Sending cron output to a file with a timestamp in its name

I have a crontab like this on a LAMP setup: 0 0 * * * /some/path/to/a/file.php > $HOME/cron.log 2>&1 This writes the output of the file to cron.log. However, when it runs again, it ...
Philip Morton's user avatar
67 votes
3 answers
304k views

crontab running as a specific user

I need to run a script daily. The script should be run as a specific user (ex. user1) not as root. So I put the cron file at /etc/cron.d and put the user name in the line (2nd column). But it gives an ...
Sam Kong's user avatar
  • 933
64 votes
7 answers
92k views

Is there a way to validate /etc/crontab’s format?

I prefer to stick scheduled tasks in /etc/crontab so I can see at a glance what's scheduled to run, regardless of which user the task runs as. The only gotcha is that the format isn't validated on ...
Ben K.'s user avatar
  • 2,439
54 votes
4 answers
238k views

How to check cron logs in Ubuntu

I went to /var/log/cron but this file is empty. How to check if crontab is enabled or is running properly or not in ubuntu thanks
user avatar
52 votes
4 answers
37k views

Should I edit /etc/crontab or run crontab -e as root?

I'm setting up regular system maintenance tasks which have to run as root. I plan to use the flavour of cron which comes with Ubuntu 14.04 LTS as the default. I see the previous admin (who since left ...
marcv81's user avatar
  • 632
44 votes
4 answers
13k views

What's wrong with my cronjob syntax, I'm trying to use a backtick (`)?

Here's what I'd like to automate: 00 08 * * * psql -Uuser database < query.sql | mail [email protected] -s "query for `date +%Y-%m-%dZ%I:%M`" Here's the error message: /bin/sh: -c: line 0: ...
Terry G Lorber's user avatar
41 votes
2 answers
33k views

Run command as Linux "system" user (shell = /bin/false)

I created a "system" user in Ubuntu 11.04 (adduser --system) for running certain cron jobs, but sometimes I want to test things out by manually running commands as that user. What's the easiest way to ...
EMP's user avatar
  • 5,162
36 votes
16 answers
51k views

Can't run AWS CLI from CRON (credentials)

Trying to run a simple AWS CLI backup script. It loops through lines in an include file, backs those paths up to S3, and dumps output to a log file. When I run this command directly, it runs without ...
binaryorganic's user avatar
32 votes
1 answer
46k views

What's the difference between /etc/cron.d and /var/spool/cron?

The crontabs on RHEL seem to be duplicated in two places, /etc/cron.d, and /var/spool/cron. I've checked, and neither of these are simlinks to the other, and neither are any of the crons contained in ...
Bart B's user avatar
  • 3,507
31 votes
6 answers
7k views

Outgrowing cron: what's the next scheduler? [closed]

We've been using cron for about as long as I can remember to handle all of our job scheduling needs. Everything from storage clones/snapshots to reports against databases to daily system reports to ...
Cakemox's user avatar
  • 25.5k