I am on Red Hat Enterprise Linux 5.x server. Is there is an easy way to run script or command at boot time after fresh reboot command?
crontab is the program used to install, deinstall or list the tables used to drive the cron daemon in Vixie Cron. Each user can have their own crontab, and though these are files in /var/spool/cron/crontabs, they are not intended to be edited directly. You or user can use crontab program to edit cron jobs.
Running job at statup (boot)
You need to use special string called @reboot. It will run once, at startup after reboot command.
@reboot /path/to/job
@reboot /path/to/shell.script
@reboot /path/to/commandThis is an easy way to give your users the ability to run a shell script or command at boot time without root access. First, run crontab command:
$ crontab -e
OR
# crontab -e -u UserName
# crontab -e -u vivek
Run a script called /home/vivek/bin/installnetkit.sh
@reboot /home/vivek/bin/installnetkit.sh
You also need to enable crond service via sys v / BSD init style system. Under RHEL / CentOS / Fedora, you need to use chkconfig (ntsysv) command to enable crond on boot:
# chekconfg crond on
Under Debian / Ubuntu Linux use update-rc.d as follows to turn on service on boot:
# update-rc.d cron defaults
Save and close the file. For further information read out tutorial on cron jobs.
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{ 2 comments… read them below or add one }
OK, But some caveats here.
1. Only works after a reboot. If you do a shutdown, or if the box crashes (as in plug vs vacuum) …. and then start, it doesn’t get run.
2. The @reboot command is not universal, especially missing on systems running micro or embedded Linux.
3. There is an alternate. the file /etc/rc.local is a place were you can place a command string to be run on boot, regardless of the means by which the system went down. Yes I know many Linux purists in favor of SysV style init scripts. However for a quick on liner it’s perfect. Here also gets run if you do a warm restart (as in go to init level 1 and then back to 3 or 5). Best this works across a very wide if not all spectrum of Linux systems. Anything in this file is always the last thing to run prior to login prompt appearing.
4. Write an init script, and put it in /etc/init.d with the appropriate run levels and timing. Harder to do and get right, somewhat, but it is the correct way to create an init entry. It also would allow for you to fine tune the timing. (need to run this job before something else gets started? Use this method)
Nice..
linuxrebel is just looks ..right…but will an normal .sh script run on boot up if we put it in specified run level script like rc3.d ?…or what we need to do to follow what Linuxrebel said above??
Thanks Vk & Lr