How can I delete or clear all the cron job that I made previously and just run new cron job that I assigned? I'm using crontab -r but it just clear in the crontab display, but it still runs that cron job and the previous cron job that I have already deleted by using that code.
After I clear cron job using crontab -r, I run crontab -l and it shows this output.
No crontab for trygcp
Use this command,
crontab -e
to access crontab, in there you can deleted specific line or job you created.
About the output you are getting, that only means there is no crontab created under the username trygcp
What you can do is this:
crontab -u [username] -e
Where:
-u define user
-e edit user's crontab
This command will create a crontab under your username, but remember you must have root privilege for you to do this.
Related
By accident made 2 different crontabs:
First with sudo crontab -e
Second with crontab -e
Just asking what happens (because did not find an explanation):
1) If they are different, are both being executed?
2) If both are identical, which one is executed? Or prone to a 'collision'?
Running sudo crontab -e will create cron tasks for the root account, and these tasks will be executed as root. Running crontab -e without sudo will create cron tasks for your user, and the tasks will be executed as that user.
Each user can have his own crontab. The first one will be executed from root, as you ran it with sudo, and the second one from your own user.
I want to edit system cron tab (/etc/crontab). I read that crontab -e is the best way to edit crontab and you need not restart cron services if you edit this way. However I am not able to edit /etc/crontab using crontab -e (this command edits the crontab associated with the user, not system crontab). So is there any better way of editing /etc/crontab (other than using VI editor- which I am doing now). Do I need to restart cron services if I edit /etc/crontab using VI edior?
There are two ways of cronjobs, one is by editing /etc/crontab and sending a SIGHUP the cron daemon. The other way is to use crontab -e to edit
a crontab entry, which is done for the current user or the one mentioned with -u. The -u option can only be used by root. The crontabs
created this way can be found in the directory
/var/spool/cron/crontabs/
and are named after the user with which uid the jobs will be started. In this case you don't need to SIGHUP cron, a normal user can't do this anyway.
Note: The syntax is slightly different to /etc/crontab: You can't enter an other user name to execute the cronjob.
You could do something like this
echo "0 23 * * * yum -y update > /dev/null 2>&1" >> /var/spool/cron/root
Then verify with
crontab -l
I've always used cpanel to set up con jobs but I don't have cpanel now.
So I added a PHP file in the cron.hourly but I want to be sure it will run.
There must be some way to do this. Like a command that lists all the cron jobs that exist?
I am on Debian 7 64 bit.
If you use crontab -e the crontab job will be syntax-checked
If you are just editing /etc/crontab or /etc/cron.*/* there is no automatic checking
nothing will check the code of your job will actually run successfully.
To list all cron jobs for a user:
crontab -u <user> -l
To list all cron jobs for root:
crontab -l
I have following questions on cron.
What is the preferred way for automating cron jobs? Using a) crontab command-line options (eg. crontab -e) or b) editing /etc/crontab. What is the difference between the two? It's not exactly clear to me.
Is crontab user specific? If I am logged in as a a user say "anup", and add jobs using crontab -e, will the job be user-specific? However, in some of the cron examples I checked online, username is provided as a field between the time string and the command to be executed.
Can the 'Mail to user" option be controlled for each job? As in, for job 1: MailTO: root for job 2: MailTO: anup.
The crontab utility is a commandline tool that maintains the crontab files for individual users.
crontab -l lists/views the crontab for the current user
crontab -e edits the crontab
You can type man crontab for full documentation on most linux/mac systems.
The crontab is specific to the user. If you're logged in as anup, then crontab -e will edit anup's crontab file. You can specify the user with the -u flag (crontab -u)
I'm not 100% sure, but I believe that you can specify a new MAILTO= setting and it will take effect for all processes executed afterwards.
I want to get the details of the last run cron job. If the job is interrupted due to some internal problems, I want to re-run the cron job.
Note: I don't have superuser privilege.
You can see the date, time, user and command of previously executed cron jobs using:
grep CRON /var/log/syslog
This will show all cron jobs. If you only wanted to see jobs run by a certain user, you would use something like this:
grep CRON.*\(root\) /var/log/syslog
Note that cron logs at the start of a job so you may want to have lengthy jobs keep their own completion logs; if the system went down halfway through a job, it would still be in the log!
Edit: If you don't have root access, you will have to keep your own job logs. This can be done simply by tacking the following onto the end of your job command:
&& date > /home/user/last_completed
The file /home/user/last_completed would always contain the last date and time the job completed. You would use >> instead of > if you wanted to append completion dates to the file.
You could also achieve the same by putting your command in a small bash or sh script and have cron execute that file.
#!/bin/bash
[command]
date > /home/user/last_completed
The crontab for this would be:
* * * * * bash /path/to/script.bash
/var/log/cron contains cron job logs. But you need a root privilege to see.
CentOs,
sudo grep CRON /var/log/cron