Cron is used to execute scheduled commands. It acts as a task scheduler on Linux and UNIX systems which will execute commands at specified times set by the user. Cron has a great deal of customization and is often used on server environments where common tasks are run on a regular basis.

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347
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5answers
669k views

Where is the cron / crontab log?

I want to verify if my cron job is executing and what time. I believe there is a log for my sudo crontab -e jobs, but where? I searched google and it I found references to look in /var/log (...
275
votes
5answers
423k views

How do I set up a Cron job?

I want to schedule a task to run on a regular basis and have heard that Cron is the way to do this. How do I add Cron jobs in Ubuntu?
274
votes
40answers
432k views

Reasons why crontab does not work

Often, crontab scripts are not executed on schedule or as expected. There are numerous reasons for that: wrong crontab notation permissions problem environment variables This community wiki aims ...
111
votes
4answers
167k views

Where is the user crontab stored?

Since upgrading my user's crontab has been wiped out. This is not the first time this has happened this year and it's a pain restoring it each time. I'd like to be able to back up the crontab for my ...
70
votes
6answers
117k views

“(CRON) info (No MTA installed, discarding output)” error in the syslog

I have a fresh install of Ubuntu 12.04.1 LTS an a number of servers. I have not added any cron jobs or edited my crontab on those servers, however, at around the same time for each machine, I get a ...
51
votes
3answers
93k views

How to run a cron job using the sudo command

Is it possible to run a cron job which needs the sudo command? Like: sudo rm somefile
50
votes
5answers
54k views

How are administrators supposed to read root's mail?

What is the Ubuntu way for system administrators to receive system notifications, which typically take the form of e-mail sent to the root account? Examples of such notifications are the output of ...
42
votes
7answers
43k views

Changing default crontab editor

I am trying to change the default editor from nano to vim. I have run the following commands: sudo update-alternatives --config editor and update-alternatives --config editor Both now output: ...
33
votes
5answers
26k views

Cron.hourly won't run

Ok, So I've made my script, I dropped it in /etc/cron.hourly then I chmod 777 the file but it won't run (automatically). If I manually run it, it works fine. Do I need to do anything else?
29
votes
2answers
37k views

How do I make cron email my @gmail account

I have a couple of cron jobs that somethime produce error output and would like to get a notification in my "real" email account, since I don't use my user's mailbox in my Ubuntu laptop, but cron (or ...
27
votes
6answers
67k views

How do you set the timezone for crontab?

I have set up ACPI wakeup so my laptop wakes up at a certain time each morning. The timezone for this is UTC. I want to set up my crontabs also using UTC so they fit with the wakeup alarm. How do ...
23
votes
7answers
118k views

How to run scripts every 5 seconds using cron?

I have a script that needs to be run every five seconds. I know that cron can do tasks by the minute, but is there a way to run something every second?
23
votes
3answers
42k views

At what time does cron execute daily scripts?

If I place a shell script in /etc/cron.daily/, at what time of the day will it be executed?
23
votes
2answers
122k views

Script doesn't run via crontab but works fine standalone

I have a script that reminds me to restart my computer if uptime is more than, say 3 days (although its set to 0 days now just to check if the script is running as my computer has been up only over a ...
21
votes
4answers
87k views

Verify if crontab works

I want to verify if a certain crontab works properly. I have added a job like this: */2 * * * * /path_to_my_php_script/info.php >/dev/null 2>&1 I know that i redirect to the null device,...
19
votes
1answer
22k views

Add lines to cron from script

Is there a way to add lines to a user's cron via script? I usually do it using crontab -e, but I would like to automate this task with a shell script.
18
votes
3answers
53k views

How to execute command every 10 seconds (without cron)?

When I execute cron I get this fault cron: can't open or create /var/run/crond.pid: Permission denied So, how to do it without cron? P.S. I want to check if file in svn has changed and I have a ...
16
votes
3answers
11k views

Can symlinks be used in /etc/cron.d/?

I'm trying to implement a configuration mechanism that allows in a certain project to deploy through svn a cron configuration. I immediately thougt that what I should do is cerate symlinks from /etc/...
15
votes
4answers
56k views

How can I tell if my hourly cron job has run?

I have created a file called ntpdate in /etc/cron.hourly #!/bin/sh /usr/sbin/ntpdate-debian date > /tmp/william_tmp date > /william_tmp date > ~/william_tmp echo test I also did Chmod 755 ...
15
votes
8answers
8k views

Notify-send doesn't work from crontab

I made a script that should notify me when there's a new chapter of manga that I'm reading. I used the command notify-send to do this. The program works when I am trying to run it in terminal. The ...
15
votes
2answers
24k views

Why do I see a CRON session opening and closing every hour in /var/log/auth.log?

I am quite fresh with Linux as a whole, so this may be a silly question - but I would still like to know the answer This morning when I look at my /var/log/auth.log (which I've been told to make a ...
15
votes
3answers
38k views

Cron Job Not Running?

I have a crontab file that looks like this: * * * * * /home/abliskovs/update/update.sh However when I check the syslog for evidence that the job has run, there is nothing that might indicate that it ...
14
votes
1answer
1k views

What happens if you use @reboot reboot in crontab file?

What would happen if you use: sudo crontab -e And add the line: @reboot reboot Will it go into a infinite loop of rebooting?!
14
votes
1answer
2k views

What is the story behind the default times set in /etc/crontab?

To my understanding, this is the default configuration of /etc/crontab: # m h dom mon dow user command 17 * * * * root cd / && run-parts --report /etc/cron.hourly 25 6 * * * ...
13
votes
2answers
19k views

How to run crontab as user:www-data?

My LAMP is setup to work as user:www-data and all files and folders are created with that permissions. I have setup for crontab as user@ubuntu. So i do crontab -e and use this command: */5 * * * ...
13
votes
4answers
12k views

Why does apt-get fail when automated with cron?

I'm trying to use cron to automate my system updates. You can see my crontab, commands, and resulting errors below. When I run upgrades.sh as root, the script runs fine. When cron runs it, apt-get -y ...
12
votes
3answers
19k views

How can I setup a Mail Transfer Agent?

I intend to use mutt to send automated emails via cron or at with attachments to my gmail address when particular events happen on my Ubuntu server. Currently, mutt cannot send email to external ...
12
votes
3answers
4k views

what can be causing /etc/cron.daily/apt to hang?

Lately I've been getting a mail from the server every day, Subject Cron <root@host> test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily ) Body /etc/cron.daily/...
11
votes
4answers
33k views

How to restart every 30 minutes automatically?

I would like to schedule a restart of my Ubuntu every 30 minutes. Is there any command or a graphical way to do it?
11
votes
5answers
10k views

Generic solution to prevent a long cron job from running in parallel?

I am looking for a simple and generic solution that would allow you to execute any script or application in crontab and prevent it from running twice. The solution should be independent on the ...
11
votes
4answers
11k views

What kind of harm there is from removing (purging) package apt-xapian-index?

I know you can't use Quick filter in Synaptic after purging apt-xapian-index, but is there something more severe? I know there are some performance issues, when you have it: https://bugs.launchpad....
10
votes
2answers
58k views

How can I see/stop current running crontab tasks?

How can I see crontab tasks which are in progress? How can I stop crontab tasks which are in progress, manually? Is [this] question about see the current running cron processes? Yes To kill ...
10
votes
4answers
8k views

“Backup Intervals” in rsnapshot.conf?

A simple question about rsnapshot. In order to perform daily backups I'm going to add lines to cron in my Ubuntu. Then, why do I have also these lines in the rsnapshot.conf ? #######################...
10
votes
3answers
13k views

Why is this rsync + ssh cron job giving me 'Permission denied (publickey)' errors?

I make frequent backups to a local drive which I want to sync daily to a remote server. The target server is configured for SSH key (no password) access only. Since my primary SSH key for that server ...
10
votes
2answers
1k views

How to schedule time-of-day upgrades

I'm responsible for about 30 Ubuntu computers at a private K-8 school. We have only a 3Mbps internet connection serving the entire campus, and I would like to ensure that updates are done in the ...
9
votes
2answers
780 views

Announce the time on the hour?

On the mac there is a feature which allows you to get your computer to verbally announce the time on the hour, is there something similar on Ubuntu? That is is there a package which already does this ...
9
votes
2answers
382 views

Make a new archive once per minute using “crontab”

I am trying to make a crontab that makes a new .tar file each minute every business day by using the following code: */1 * * * 1,2,3,4,5 tar -cf /home/user/Archiv/$(date +"%Y%m%d%H%M").tar /home/user/...
9
votes
2answers
12k views

Where are cron logs stored on Ubuntu 14.04?

I am trying to troubleshoot why my cron task isn't working sometimes. Where does cron store log files by default? Is it /var/log/syslog ? I have looked at that file and it is empty. Do I need to ...
9
votes
3answers
747 views

How to persist on a wifi connection after disconnection?

I've got a Ubuntu machine running a software that requires internet. However, sometimes the wifi fails (router reboot for example) and doesn't find the network again, until I manually service network-...
9
votes
1answer
7k views

Does ubuntu support “@reboot” in crontab

Does ubuntu support "@reboot" in crontab ? I find documentation suggesting it is supported, but web chatter asserts it is not. I cannot make the @reboot section work. The "after midnight" section ...
9
votes
2answers
15k views

All commands in my crontab fail with “Permission denied”

Update: This issue will not be answered conclusively; I have moved to another distro and have not observed this problem since. I was never able to fix it with the insightful answers available at the ...
8
votes
5answers
19k views

cron.daily jobs not running

I created 3 daily cron jobs to run. Below are the three that are placed in etc/cron.daily rkhunter.sh #!/bin/sh ( rkhunter --versioncheck rkhunter --update rkhunter --cronjob --report-warnings-only ...
8
votes
3answers
39k views

How do I configure exim4 to send mail through a password protected ssl smtp mail server?

I'd like my cronjobs to be able to send mail from my home computer. My servers configure exim4 like this: dc_eximconfig_configtype='internet' dc_other_hostnames='' dc_local_interfaces='127.0.0.1' ...
8
votes
2answers
3k views

How to start a GUI application from cron?

I need to run a Java applet from a Firefox. The problem is, I need to run this Firefox from a cron. If I run from the command line and its work fine, but when put the command in the cron it failed: */...
8
votes
3answers
13k views

Ubuntu 14.04 not running Bash scripts in /etc/cron.daily [duplicate]

I have a few scripts (that currently run in a CentOS system) I have moved to a new Ubuntu 14.04 system. These scripts are in the /etc/cron.daily to run once a day. These scripts are to run at the ...