Run bash script as daemon

Question

I have a script  which runs my PHP script each X times      bin bash while true  do  usr bin php -f   my-script php echo  Waiting     sleep 3 done   How can I start it as daemon

User · Answer

A Daemon is just program that runs as a background process, rather than being under the direct control of an interactive user...

[The below bash code is for Debian systems - Ubuntu, Linux Mint distros and so on]

The simple way:

The simple way would be to edit your /etc/rc.local file and then just have your script run from there (i.e. everytime you boot up the system):

sudo nano /etc/rc.local

Add the following and save:

#For a BASH script
/bin/sh TheNameOfYourScript.sh > /dev/null &

The better way to do this would be to create a Daemon via Upstart:

sudo nano /etc/init/TheNameOfYourDaemon.conf

add the following:

description "My Daemon Job"
author "Your Name"
start on runlevel [2345]    

pre-start script
  echo "[`date`] My Daemon Starting" >> /var/log/TheNameOfYourDaemonJobLog.log
end script

exec /bin/sh TheNameOfYourScript.sh > /dev/null &

Save this.

Confirm that it looks ok:

init-checkconf /etc/init/TheNameOfYourDaemon.conf

Now reboot the machine:

sudo reboot

Now when you boot up your system, you can see the log file stating that your Daemon is running:

cat  /var/log/TheNameOfYourDaemonJobLog.log

• Now you may start/stop/restart/get the status of your Daemon via:

restart: this will stop, then start a service

sudo service TheNameOfYourDaemonrestart restart

start: this will start a service, if it's not running

sudo service TheNameOfYourDaemonstart start

stop: this will stop a service, if it's running

sudo service TheNameOfYourDaemonstop stop

status: this will display the status of a service

sudo service TheNameOfYourDaemonstatus status

User · Answer

You can go to  etc init d  - you will see a daemon template called skeleton   You can duplicate it and then enter your script under the start function

User · Answer

Another cool trick is to run functions or subshells in background  not always feasible though  name      echo  Do something    sleep 1      put a function in the background name  amp   Example taken from here  https   bash cyberciti biz guide Putting functions in background   Running a subshell in the background   echo  started   sleep 15  echo  stopped    amp

User · Answer

Some commentors already stated that answers to your question will not work for all distributions  Since you did not include CentOS in the question but only in the tags  I d like to post here the topics one has to understand in order to have a control over his her proceeding regardless of the distribution    what is the init daemon  optional  what is the inittab file   etc inittab   what does the inittab file do in your distro  e g  does it actually run all scripts in  etc init d      For your problem  one could start the script on sysinit by adding this line in  etc inittab and make it respawn in case it terminates     start and respawn after termination ttyS0  respawn  bin sh  path to my script sh   The script has to be made executable in advance of course   chmod  x  path to my script sh   Hope this helps

User · Answer

To run it as a full daemon from a shell  you ll need to use setsid and redirect its output  You can redirect the output to a logfile  or to  dev null to discard it  Assuming your script is called myscript sh  use the following command   setsid myscript sh  gt  dev null 2 gt  amp 1  lt   dev null  amp    This will completely detach the process from your current shell  stdin  stdout and stderr   If you want to keep the output in a logfile  replace the first  dev null with your  path to logfile   You have to redirect the output  otherwise it will not run as a true daemon  it will depend on your shell to read and write output

[linux] Run bash script as daemon

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