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

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System Crontab or Root Crontab

System crontab: /etc/crontab Root crontab: sudo crontab -u root -e Which way is preferred? As they all run tasks within administration privilege.
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2answers
473 views

Automating backups run from a bash script in Linux the right way

I have a bash script I wrote to backup a Moodle installation. It works fine, I've tested the backups, but there's a problem with it; when I do the backups, since I have to use sudo to type the ...
2
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1answer
194 views

Executing PHP with CronJobs in CentOS 6.4 not working?

So I've spent around 2-3 hours now and some times researching, I found several of the same responses online but none seem to work! I'm trying to execute a PHP script every minute (as a test), but it ...
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1answer
167 views

How to set up a cron entry that runs at 00 and 30 after the hour?

I have a cron entry that runs every 30 minutes - */30 * * * * /home/myuser/myscripts.sh How to set this up such that it runs exactly at 30 minute intervals but also exactly at (for example) 3:00 ...
1
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2answers
77 views

Running a cron job from another shell

I would like cron to run a script from a specific shell (Zsh). I thought the following would work: 00 02 * * * exec zsh; /path/to/script.sh but apparently it doesn't, why? This also made me ...
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0answers
27 views

How to block the user for a certain amount of time

Suppose, I am working in X environment, and I want to have an obligatory periodic rest. Is it possible to setup a root cron job, that will block my user for 5 minutes every 45 minutes? I am using ...
2
votes
1answer
227 views

Why do deleted files continually reappear?

I've been having a strange issue recently, where I would delete files from a location (i.e. Desktop), and then empty the Trash. However, a day or so later (I'm not sure exactly what triggers it), the ...
27
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10answers
13k views

Correct locking in shell scripts?

Sometimes you have to make sure that only one instance of a shell script is running at the same time. For example a cron job which is executed via crond that does not provide locking on its own (e.g. ...
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0answers
202 views

why daily cron isn't running on CentOS 6?

I have a daily cronjob set up on CentOS 6 OS which should look after the log rotation job. The file is /etc/cron.daily/logrotate and it's contents are #!/bin/sh /usr/sbin/logrotate ...
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1answer
200 views

security concern around adding cron user to web application group

I have a permissions issue on my CentOS 5.6 machine with regards to the cron user. On my test/staging environment my cron user (picco-cron) is a member of one group - picco-cron, as below: ...
4
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2answers
11k views

How to start a cron job without reboot?

I use a cron job to call offlineimap every 2 minutes: */2 * * * * /usr/bin/offlineimap > ~/Maildir/offlineimap.log 2>&1 I needed to kill the cron job to fix a problem. How can I then ...
3
votes
1answer
378 views

How do I push a Mercurial repository to BitBucket over ssh? [closed]

I created a public key for ssh and registered that key with BitBucket. I then attempted to push: $ hg push ssh://jhayward@bitbucket.org/johncharrell/[project name] pushing to ...
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1answer
91 views

Why CRONTAB tasks are lost when quit Putty session? [closed]

I logged to remote computer, running under Solaris, using Putty and added some jobs to be run by cron. When I quit console and logged once again all jobs was lost. crontab -l myuser How do I ...
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1answer
168 views

automate updates with a bash script and cron

I'm trying to automatize the updates of debian system, without making upgrades. Then i'll send an e-mail to me, everytime there is an upgrade available. I've tryied to do it with cron-apt, but i ...
5
votes
0answers
167 views

CRON Permission Denied [closed]

I have a Debian 7. 3 Server with WebMin installed. I configured a cron job to run every minute as root user, so I run the command crontab -l when I'm logged in as root it shows: * * * * * ...
2
votes
4answers
2k views

Crontab not working

I'm trying execute a basic shutdown crontab to run M-F at 10PM. So I did the following: sudo crontab -e Once inside of the crontab I added the following line: 0 22 * * 1-5 shutdown now The job ...
2
votes
1answer
64 views

How could I signal to a cron job to skip runs?

I have a cron job that runs every X mins and that I would like to have a way to "signal" it not to do anything if needed. Is there a standard way for this? The only idea I had is to check some ...
3
votes
2answers
146 views

Does cron know that the instance to be scheduled is already running?

I was wondering if we add a job in the crontab e.g. to run every 5 mins and the job does not actually manage to finish in 5 mins, does the cron daemon know that the previous instance is already ...
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vote
2answers
433 views

Crontab not triggered

I have a program written in C with OpenCV. It captures an image from the webcam and saves on the disk with the name given as an argument. I want to trigger it every minute, thus I inserted the ...
0
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1answer
203 views

Getting a Bad Hour Error in crontab

I am getting Bad Hour error for below peice of code in crontab */05 17-05 * * * wget -q -O /dev/null "http://abcd/cron/abcd" Is there any issue with this. I want the cron to run from evening 5 PM ...
0
votes
1answer
164 views

Cron task starts at 5:30 and runs every 5 mins once

I want to run a crontab cron job which start at 5:30 AM and runs every 5 mins. How do i set it up in Linux? I am able to give like below. But how do i make it 5:30 ? */05 5-16 * * *
2
votes
1answer
70 views

Accidentally typed crontab with just the dash

What happens when I type just "crontab -"? The "e" didn't take before I hit Enter. It just moved the cursor to the next line and I had to Ctrl+C to exit, but I'm not sure what it did exactly. I'm on ...
2
votes
1answer
414 views

cronjob for automatic DB backup to date prefixed file

I am using the latest Linux Mint. I was wondering if it's possible to create a special cronjob for a database backup. In my /etc/cronjob file I have the following code: # Minute Hour Day of ...
0
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1answer
91 views

Can continually assigning a variable in a shell script cause a memory leak?

I've written a short script to copy Apache's server status to a log: #Save date and time to a variable dt=$(date) #Echo date and time to the log file as it's not included in server-status echo "Time ...
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1answer
289 views

Cron: Client does not have permissions to send as this sender

Platform: Arch Linux Cron: cronie Mail: msmtp I discovered that sending cron output to a mailbox hosted by Office 365 produced the following error, even though sending mail through the CLI was ...
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1answer
130 views

Cron task in graphic interface

I need to open one (or more) browser tab periodically and I decided to use cron. The command in the shell (bash) that correctly executes this task is chromium-browser http://mysite.com. If I type it, ...
0
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2answers
77 views

How can I ensure that a custom environment variable is set before cron runs a task?

I recently experienced a logwatch issue that is fixed by running export DATE_MANIP=DM5. cron seems to forget this when I logout (presumably because it's not saved). Where can I add this custom ...
2
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1answer
85 views

cron midnight 00 24 or 00 00? [closed]

My current crontab looks like this: 00 00 * * 1-5 "/home/user/script.sh" But it seems like it is not being triggered, all others are triggering fine except the one running at midnight. What is the ...
3
votes
1answer
63 views

What's the easiest way to set up a 2-hour alarm?

I want my computer to play some given .mp3 every 2 hours. I want it to run at startup, and be modifiable with a given .conf file. The choice of .mp3 will also be in the .conf file. The reason is, I ...
3
votes
2answers
80 views

How to run a command as if it is called from cron

I write a script and set it as a cron job. But due to a difference of environment variables it doesn't work as it should be. In that case I change a little bit with crontab -e and set a cron job time ...
0
votes
1answer
30 views

Crontab in Daylight Savings

This weekend with daylight savings, we had a situation that when the system clock hit 3:00am from the jump, we had hundreds of processes fire off out of the crontab. Everything I'm reading says that ...
9
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1answer
192 views

Cronjob to Run and then Terminate

I want to add a cron entry that does something like: 00 00 * * * * /tmp/script.sh Is there something I can add to the end of the line, so that when it is finished, it will remove the line out of my ...
1
vote
1answer
150 views

Why does redirection in crontab result in a zero byte file?

System: Xubuntu 13.10 When I have this crontab entry */5 * * * * cat /home/dbk/.bash_aliases &> /home/dbk/Desktop/junk junk has a byte size of 0. Running $ cat /home/dbk/.bash_aliases ...
7
votes
7answers
2k views

cron Vs. sleep - which is the better one in terms of efficient cpu/memory utilization?

The Case: I need to run some commands/script at certain intervals of time and for this I have two options - 1. set up a cron-job or, 2. implement a loop with sleep in the script itself. Question: ...
3
votes
1answer
10k views

Crontab job start +1 min after @reboot

Need a script executed at each reboot in +1 minute. I placed a record @reboot but it is too early for my script. How to execute it sometime after reboot?
0
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2answers
32 views

Cron Job - Log Each Minutes Activity [duplicate]

I have some cron jobs set up to run, some of them each minute. I know I can log them to text files by simply putting php /path/to/file.php > /var/logs/something.txt but can I do this every minute? ...
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0answers
622 views

Trying to kill cron job processes found by “ps ax | grep keyword” logged in as pi user

I'm trying to kill several processes from the command line logged into the pi as the user pi. All of the processes have been started by cronjobs, so they should belong to the root user. I'm running ...
1
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1answer
95 views

As root, how can I list the crontabs for all users?

I have a script being run automatically that I can't find in the crontab for the expected users, so I'd like to search all users' crontabs for it. Essentially I want to run a crontab -l for all ...
1
vote
2answers
294 views

How come crontab -e is different from less /etc/crontab?

Im pretty new to unix and crons, I was currently about to try to add crons to an existing cron file. I read you could do this with crontab -e. The confusing thing to me is just that crontab -e shows ...
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3answers
60 views

variables in crontab [duplicate]

On our linux server we have a lot of entries. Many entries look like this: 15 13 * * 3 /very/long/path/to/binary/run.sh ... These entries would be easier to maintain if I could write: 15 13 * * ...
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1answer
75 views

Help with “crontab -e” [duplicate]

I'm trying to learn a little about cron and would appreciate some help. I edited crontab -e to have this line: */10 * * * * /usr/bin/touch /home/dkb/Desktop/test.txt It works and I see ...
3
votes
3answers
175 views

Setting up a cron for every 30 hours in Debian

*/30 */30 * * * python /root/get_top.py I'm trying to run a script every 30 hours and 30 minutes. Is the syntax above proper for that? I've had multiple people tell me that */30 is not a valid ...
0
votes
2answers
377 views

Is a restart of cron or crond necessary after each new schedule addition or modification?

When I schedule a job, some seem to be applied immediately, while others after a reboot. So is it recommended to restart cron (crond) after adding a new cron job? How to do that properly (esp. in a ...
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votes
1answer
76 views

Is there a better way to stop and restart Apache server every 30 minutes? [closed]

I have to stop and restart Apache every 30 minutes in order to avoid it becoming extremely slow over time. The cron job that I use as follows: @echo off rem Launch google.com, wait 2 seconds, then ...
29
votes
14answers
3k 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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votes
2answers
130 views

Running cron.daily in parallel

Being able to put a script in /etc/cron.daily is really nice because I can do it easily from a configuration management system or a package. However, my understanding is that all the entries in ...
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votes
4answers
212 views

Cron not running my script

I'm not sure why but my app never executes when I reboot my machine. In crontab > crontab -e I see @reboot /root/myscriptname.sh The file is #!/bin/bash nohup mono-sgen /root/myapp.exe ...
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1answer
177 views

Use /etc/init.d/fetchmail with the personnal ~/.fetchmailrc

Now, I have two users in my system using fetchmail with a personal ~/.fetchmailrc and syncing there mails with the command fetchmail -kv --uidl -m '\''/usr/bin/procmail -d %T'\ (In a cron but this ...
1
vote
1answer
129 views

Logrotate not picking up or acting on new configuration file

I had a logrotate configuration file set up for a log (let's call it Log1). It is working fine and the log is rotating everyday as expected. Yesterday I cloned this set up and modified it for three ...
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0answers
32 views

Why am I not receiving any system e-mails? [closed]

In my crontab, I have the following: * * * * * sh /home/rimmer/test.sh In /home/rimmer/test.sh I have the following: #!/bin/bash echo 'test'; I have also set chmod +x /home/rimmer/test.sh, of ...