Cron is a job scheduler that allows users to run commands periodically.

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start xscreensaver from cron@reboot, ubuntu startup, service/deamon?

I need start xscreensaver for ubuntu, and it can be started in ubuntu startup application. my question is: can xscreensaver be started in cron@reboot? can xscreensaver be started in service/deamon? ...
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80 views

run btrfs balance with cron

Since I run today in a problem with a full disk, which turns out is not unbalanced. Which you can fix with btrfs balance. So my question is: Is there any risk by ruining this by a cron job? (in ...
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1answer
39 views

Can someone be so kind as to setup a cronjob for me? [closed]

I've been trying to get cron to execute these two scripts to schedule and post on twitter, tumblr, facebook and linkedin. It worked once and never again. <?php require ...
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2answers
92 views

Cron job not behaving as expected

So I have a python script that pulls down git/svn/p4 repositories and does some writing to a database. I'm simply trying to automate the running of this script and based from what I see in syslog it ...
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15answers
4k views

Run unix command precisely at very short intervals WITHOUT accumulating time lag over time

Question I'd like to be able to run a UNIX command precisely every second over a long time period. I need a solution, which does not lag behind after a certain time, because of the time the command ...
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41 views

high precision subsecond cronjob replacement

I am looking for a cron replacement which could run subsecond schedule, is there have any "still alive" project which serve this purpose? Currently running Ubuntu 14
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1answer
111 views

crontab not executing my script?

I added this rule to the bottom of my crontab * * * * * /root/test.sh It basically resets iptables so I can fool around. If I mess up I won't be locked out of my box. When I run the script in bash ...
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2answers
64 views

Emulating /etc/cron.d/ on OSX

On most modern unixes, cron supports individual crontab files in /etc/cron.d, in which each task executes as a specified user. These files automatically update the crontab once edited. They allow ...
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249 views

Send backup by email with crontab

I use this cron job to do a backup of /home/blah/ each day at 01:00 a.m. : 0 1 * * * tar -zcf /home/blah/backup.tgz /home/blah/ In fact I would prefer that an email is sent to me with the .tgz file ...
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4answers
29k views

How do I completely silence a cronjob to /dev/null/?

On my Ubuntu-Desktop and on my debian-server I have a script which needs to be executed each minute (a script that calls the minute-tic of my space online browsergame). The problem is that on ...
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1answer
66 views

Are there disadvantages/consequences to adding scheduled tasks directly to /etc/crontab instead of using the crontab command? [duplicate]

CentOS 5.x I noticed that someone (presumably another admin) added an entry directly to the bottom of /etc/crontab so it reads like: SHELL=/bin/bash PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root ...
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66 views

Cron job — If computer inactive for x minutes turn wifi off

I would like to have an alias command in my .bashrc that could be ran at startup. That states: If computer is inactive for X minutes then turn off wifi. How would I do that? I am currently using ...
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1answer
147 views

cronjob does not execute when not logged in

SOLVED, see 'useless' answer. I have a cronjob in my crontab. When I specify the job to be executed in 2minutes, I wait, and then I can see files created by the job, I can see the process with ps. ...
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1answer
78 views

How to restart my server automatically using crontab if they went down?

I have a jar file which I am running like this in my Ubuntu 10.10 and then it starts my exhibitor server in the background - nohup java \ -jar ...
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1answer
77 views

Crontab permission problem

I have a fc19 host at work. This morning crontab did not work. $ ls -l /usr/bin/crontab ----------. 1 root root 53472 Jun 11 2013 /usr/bin/crontab The permissions -------- means no one has access ...
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3answers
285 views

Lock folder when running cron

I am setting up my first cron on a Ubuntu Desktop system. I was curious to know if there is a way to lock a folder before a cron is ran and how to set it up? I am following this article. I am just ...
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1answer
970 views

Automatically detect when a file has reached a size limit

I would like to send an email when a file reach a certain size limit. The only way I thought of doing this is by doing a cronjob which will check the file size and send the email if the file is ...
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1answer
41 views

Cron Job Not working [closed]

I have been trying to create a cron job to execute a script located in ~/Documents/script.sh at midnight every night and every 8 hours after that. I have found a lot of material on this but for some ...
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2answers
102 views

Crontab does not work properly in Ubuntu

I am learning how to use cron. I wrote some simple code in my crontab # m h dom mon dow command */1 * * * * echo "1 minute"> ~/Document/cronoutput I expected it to print the words every ...
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1answer
202 views

How to execute recurring Bash script at specific times?

How would I set a script to execute on every Tuesday and Thursday at 11:50am? I've been looking at the at command, but I can't conceive how to use it the way I need to from its man page.
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1answer
44 views

fault-tolerant crond replacement

I'm looking for a replacement to crond, or possibly an extension of it. The feature that I definitely would want to have is fault-tolerance. E.g. if a job failed to run due to the computer not being ...
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2answers
271 views

How can I peek at the output of a running crontab task on OpenBSD?

I have an hourly hour-long crontab task running with some mtr (traceroute) output every 10 minutes (that is going to go for over an hour prior to it being emailed back to me), and I want to see the ...
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7answers
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How to Find a Fugitive Crontab

A few years ago I setup a cron job to automatically ping a URL every minute as part of a monitoring system (that's oversimplification, but it'll do for this question). Because I'm a horrible person, I ...
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1answer
65 views

CentOS machine keeps “losing” active directory membership

All of our CentOS 6 machines have been joined to our active directory domain. Each of these machines eventually "loses" their domain membership, which breaks authentication for AD users. I created a ...
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1answer
72 views

Please help me to debug this notify-send battery alert script

I used crontab -e to define the following: */5 * * * * env DISPLAY=:0 /home/max/.bin/battery-check.sh The contents of the script are: #!/bin/bash ...
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2answers
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sh script will not execute as root (cron)

I have the following script added to cron. If I add touch thisisatest.file to the first line it will create a file named thisisatest.file, but not execute the rest of the code. If I manually type ...
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6answers
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What does '>/dev/null 2>&1' mean in this article of crontab basics? [duplicate]

I am reading an article about crontab There is something about disabling automatically sending emails. Disable Email By default cron jobs sends an email to the user account executing the ...
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2answers
531 views

Cannot edit crontab as non root user

When I use the command crontab -e on my Debian server as a non root user (in this case as postgres), I can't edit it because of "/tmp/crontab.SJlY0Y/crontab" [Permission Denied] crontab -l on the ...
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Shell script to monitor log files going over a certain size [duplicate]

Due to another issue I'm tracking down, one of my app servers occasionally starts generating a large amount of errors and then becomes unresponsive. For now, the simple solution is to restart the ...
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1answer
81 views

What does */13 do in a crontab?

*/n * * * * in a crontab means run every n minutes, if n divides 60 evenly. What happens for other cases, like */13 * * * *?
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Configure job to expire

I'm learning Linux at the moment and were doing some exercises scheduling jobs with cron and crontab, but I'm wondering if it's possible to limit the amount of times that the scheduled job is ran. ...
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2answers
130 views

Why does this Shell script fail as cron job [closed]

I have the following in a shell script, when I run this script it works but when I put this as a cron job it does not work(nothing happens!). How come? script #!/bin/bash ...
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641 views

Null message body; hope that's ok

I have the following command below as part of a cronjob. When I run the command via cron or at the command line, I get Null message body; hope that's ok. The contents of the email are empty but when ...
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How to do version-control repository update in crontab?

I'm trying to automate version-control repository update in crontab. The following script /home/usr/mrbean/bin/update.sh works in interactive Bash command-line: #!/bin/bash ...
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93 views

Configure cron for daily NMon task

I want to configure a cron job for NMon to gather stats during all day, everyday. Leaving a file per day to dump into NMon Analyser. I know the proper command to get a spreadsheet format its ...
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1answer
44 views

CRON path problems

I have a Python script that runs from the command line beautifully, but when I try and run it from CRON does strange things. The script generates, then runs an apk script file. The apk script file ...
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424 views

Is this sar/sysstat cron job formatted correctly?

I want it to give me all the sar/sadc options, interrupts,disk,etc.. every 10 seconds starting at noon for the entire hour. On the second line I want to capture the info in /proc/interrupts every ...
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1answer
290 views

Cron Log File Outputs Nothing

I get no output from my cronjob. The script the job is executing is: <?php require '/opt/bitnami/apps/wordpress/htdocs/wp-load.php'; ...
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Where is this cronjob running?

We have a news server running on a CentOS 6.5 box. It's leafnode, and a cron is set to run every two minutes. We decide to shut it down to troubleshoot other issues, so we comment out the line in ...
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Cron job scheduled to run on specific day-of-week is running on last day of month as well

I have a cron job scheduled to run every Thursday at 6am via the following schedule: 0 6 * * 4 It's been running as expected, but on Tues, September 30th it ran (unexpectedly) and again on ...
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1answer
130 views

To write this Pseudocode with Regex

I am doing a Makefile which I run regularly by Crontab every day at 0230 crontab -e; 30 2 * * * /bin/thePseudocode Python-like Pseudocode directories = ["Cardiology", "Rheumatology", "Surgery"] ...
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1answer
11k views

Why does cron silently fail to run sudo stuff in my script?

I have a script run from a non-privileged users' crontab that invokes some commands using sudo. Except it doesn't. The script runs fine but the sudo'ed commands silently fail. The script runs ...
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1answer
32 views

Cron, crontab -e reads the wrong file

I do a simple: crontab -e In the top of this file, I have: #DO NOT EDIT THIS FILE - edit the master and reinstall. And I see that it has opened up some temporary file under /tmp I am using ...
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8answers
40k views

How can I run a cron command with existing environmental variables?

How can I run a cron command with existing environmental variables? If I am at a shell prompt I can type echo $ORACLE_HOME and get a path. This is one of my environmental variables that gets set in ...
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2answers
266 views

cron will find certain commands on the PATH but not others

Having issues making crontab run certain commands, despite the PATH and SHELL being set correctly. Here is the env of the machine: SHELL=/bin/bash USER=ubuntu MAIL=/var/mail/ubuntu ...
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3answers
2k views

Cron job to check if PHP script is running, if not then run

I am wondering if someone might point me in the right direction. I've got little experience working with the Linux command line and recently due to various factors in work I've been required to gain ...
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1answer
1k views

Why aren't crontabs stored in user home directories?

I'm curious to know: why are crontabs stored in /var rather than in the user's home directories? It makes it a total pain to isolate these files for upgrades but I suspect that there is a logical ...
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1answer
34 views

Need to automate the updating of the crontab file

We have an automated process where a server is built, and after applications/middleware are installed using another automated process, and the crontab needs to be updated for those ...
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2answers
71 views

Do spaces matter in a crontab

It's not clear to be from the manpage for crontab. IS extra white space allowed between the fields? e.g., if I have this: 1 7 * * * /scripts/foo 5 17 * * 6 /script/bar 31 6 * * 0 /scripts/bofh is ...
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1answer
48 views

High precision scheduler daemon

I'm looking for a scheduler daemon like cron, but with at least seconds precision so I can use it for a radio automation app. I've heard conflicting rumors about cron's ability to handle seconds. If ...