Cronjob run program only if other programm is already running












1















how do i run a cronjob only when another service is already up running and while the programm itself is not already running? It is important that programm2 starts only after programm1 is already up.



*/2 * * * * check if programm1 one is running ; check if programm2 is not running ; /etc/init.d programm2 start






cron







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  • 4





    Services that depend on other services... sounds like a task for systemd.

    – danzel
    yesterday
















1















how do i run a cronjob only when another service is already up running and while the programm itself is not already running? It is important that programm2 starts only after programm1 is already up.



*/2 * * * * check if programm1 one is running ; check if programm2 is not running ; /etc/init.d programm2 start






cron







share|improve this question







New contributor




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  • 4





    Services that depend on other services... sounds like a task for systemd.

    – danzel
    yesterday














1












1








1








how do i run a cronjob only when another service is already up running and while the programm itself is not already running? It is important that programm2 starts only after programm1 is already up.



*/2 * * * * check if programm1 one is running ; check if programm2 is not running ; /etc/init.d programm2 start






cron







share|improve this question







New contributor




La Fleur is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.












how do i run a cronjob only when another service is already up running and while the programm itself is not already running? It is important that programm2 starts only after programm1 is already up.



*/2 * * * * check if programm1 one is running ; check if programm2 is not running ; /etc/init.d programm2 start






cron




cron






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La Fleur is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|improve this question







New contributor




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Check out our Code of Conduct.









share|improve this question




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asked yesterday









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Check out our Code of Conduct.








  • 4





    Services that depend on other services... sounds like a task for systemd.

    – danzel
    yesterday














  • 4





    Services that depend on other services... sounds like a task for systemd.

    – danzel
    yesterday








4




4





Services that depend on other services... sounds like a task for systemd.

– danzel
yesterday





Services that depend on other services... sounds like a task for systemd.

– danzel
yesterday










1 Answer
1






active

oldest

votes


















1














You could write a script using the $? variable. This variable contains the exit status of the last program; so if you run systemctl status dnsmasq and it's active, running echo $? will return 0 which means true. If it's not active, $? will return a non-0 answer, which means false.



A simple script to achieve this function would be:



#/!bin/bash

x=1

while [ "$x" != "0" ]

do

 systemctl status (service to monitor)

 if [ "$?" = "0" ]

 then

  systemctl start (service to start)

  break

 else

  sleep 30

  continue

 fi

done


Line 1 = sets a variable to non-zero so a loop can be run from it



Line 2 = starts a loop that runs continuously (x can never = 0)



Line 4 = checks if a service is running, which sets $? to a zero or non-zero
value



Line 5 onward = checks if the exit status of the last command (checking if the service is running) was true or false. if it's true (zero), it starts the next service and breaks out of the loop. If it's false (non-zero) it returns to the start of the loop and runs until the selected service is running.



You could either run this script at startup or turn it into a service of its own.



You would need to run it as root, whichever your choice, since you're starting/stopping system services.






share|improve this answer





















  • 1





    You are re-implementing the systemd attributes Requires= and/or BindsTo= and/or After=. Also, the while loop will probably make the CPU fans blow because it re-runs systemctl without any pause.

    – PerlDuck
    yesterday








  • 1





    @perlduck added a 30 second sleep in the else statement to address the inefficiency of running the script continuously. In regards to the former, the asker wanted a cronjob so I figured a simple script would be the most flexible solution, though not the most efficient. Thanks for the pointers.

    – Minty
    yesterday











  • @Minty if this script is called by the cronjob mentioned by the asker, wouldn't this queue a new instance of your script every 5 minutes if the service it is waiting for is not running? If you're already using systemd, you might as well use systemd timer instead of cron and the mechanisms mentioned by PerlDuck for a pure systemd solution.

    – danzel
    21 hours ago











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1














You could write a script using the $? variable. This variable contains the exit status of the last program; so if you run systemctl status dnsmasq and it's active, running echo $? will return 0 which means true. If it's not active, $? will return a non-0 answer, which means false.



A simple script to achieve this function would be:



#/!bin/bash

x=1

while [ "$x" != "0" ]

do

 systemctl status (service to monitor)

 if [ "$?" = "0" ]

 then

  systemctl start (service to start)

  break

 else

  sleep 30

  continue

 fi

done


Line 1 = sets a variable to non-zero so a loop can be run from it



Line 2 = starts a loop that runs continuously (x can never = 0)



Line 4 = checks if a service is running, which sets $? to a zero or non-zero
value



Line 5 onward = checks if the exit status of the last command (checking if the service is running) was true or false. if it's true (zero), it starts the next service and breaks out of the loop. If it's false (non-zero) it returns to the start of the loop and runs until the selected service is running.



You could either run this script at startup or turn it into a service of its own.



You would need to run it as root, whichever your choice, since you're starting/stopping system services.






share|improve this answer





















  • 1





    You are re-implementing the systemd attributes Requires= and/or BindsTo= and/or After=. Also, the while loop will probably make the CPU fans blow because it re-runs systemctl without any pause.

    – PerlDuck
    yesterday








  • 1





    @perlduck added a 30 second sleep in the else statement to address the inefficiency of running the script continuously. In regards to the former, the asker wanted a cronjob so I figured a simple script would be the most flexible solution, though not the most efficient. Thanks for the pointers.

    – Minty
    yesterday











  • @Minty if this script is called by the cronjob mentioned by the asker, wouldn't this queue a new instance of your script every 5 minutes if the service it is waiting for is not running? If you're already using systemd, you might as well use systemd timer instead of cron and the mechanisms mentioned by PerlDuck for a pure systemd solution.

    – danzel
    21 hours ago
















1














You could write a script using the $? variable. This variable contains the exit status of the last program; so if you run systemctl status dnsmasq and it's active, running echo $? will return 0 which means true. If it's not active, $? will return a non-0 answer, which means false.



A simple script to achieve this function would be:



#/!bin/bash

x=1

while [ "$x" != "0" ]

do

 systemctl status (service to monitor)

 if [ "$?" = "0" ]

 then

  systemctl start (service to start)

  break

 else

  sleep 30

  continue

 fi

done


Line 1 = sets a variable to non-zero so a loop can be run from it



Line 2 = starts a loop that runs continuously (x can never = 0)



Line 4 = checks if a service is running, which sets $? to a zero or non-zero
value



Line 5 onward = checks if the exit status of the last command (checking if the service is running) was true or false. if it's true (zero), it starts the next service and breaks out of the loop. If it's false (non-zero) it returns to the start of the loop and runs until the selected service is running.



You could either run this script at startup or turn it into a service of its own.



You would need to run it as root, whichever your choice, since you're starting/stopping system services.






share|improve this answer





















  • 1





    You are re-implementing the systemd attributes Requires= and/or BindsTo= and/or After=. Also, the while loop will probably make the CPU fans blow because it re-runs systemctl without any pause.

    – PerlDuck
    yesterday








  • 1





    @perlduck added a 30 second sleep in the else statement to address the inefficiency of running the script continuously. In regards to the former, the asker wanted a cronjob so I figured a simple script would be the most flexible solution, though not the most efficient. Thanks for the pointers.

    – Minty
    yesterday











  • @Minty if this script is called by the cronjob mentioned by the asker, wouldn't this queue a new instance of your script every 5 minutes if the service it is waiting for is not running? If you're already using systemd, you might as well use systemd timer instead of cron and the mechanisms mentioned by PerlDuck for a pure systemd solution.

    – danzel
    21 hours ago














1












1








1







You could write a script using the $? variable. This variable contains the exit status of the last program; so if you run systemctl status dnsmasq and it's active, running echo $? will return 0 which means true. If it's not active, $? will return a non-0 answer, which means false.



A simple script to achieve this function would be:



#/!bin/bash

x=1

while [ "$x" != "0" ]

do

 systemctl status (service to monitor)

 if [ "$?" = "0" ]

 then

  systemctl start (service to start)

  break

 else

  sleep 30

  continue

 fi

done


Line 1 = sets a variable to non-zero so a loop can be run from it



Line 2 = starts a loop that runs continuously (x can never = 0)



Line 4 = checks if a service is running, which sets $? to a zero or non-zero
value



Line 5 onward = checks if the exit status of the last command (checking if the service is running) was true or false. if it's true (zero), it starts the next service and breaks out of the loop. If it's false (non-zero) it returns to the start of the loop and runs until the selected service is running.



You could either run this script at startup or turn it into a service of its own.



You would need to run it as root, whichever your choice, since you're starting/stopping system services.






share|improve this answer















You could write a script using the $? variable. This variable contains the exit status of the last program; so if you run systemctl status dnsmasq and it's active, running echo $? will return 0 which means true. If it's not active, $? will return a non-0 answer, which means false.



A simple script to achieve this function would be:



#/!bin/bash

x=1

while [ "$x" != "0" ]

do

 systemctl status (service to monitor)

 if [ "$?" = "0" ]

 then

  systemctl start (service to start)

  break

 else

  sleep 30

  continue

 fi

done


Line 1 = sets a variable to non-zero so a loop can be run from it



Line 2 = starts a loop that runs continuously (x can never = 0)



Line 4 = checks if a service is running, which sets $? to a zero or non-zero
value



Line 5 onward = checks if the exit status of the last command (checking if the service is running) was true or false. if it's true (zero), it starts the next service and breaks out of the loop. If it's false (non-zero) it returns to the start of the loop and runs until the selected service is running.



You could either run this script at startup or turn it into a service of its own.



You would need to run it as root, whichever your choice, since you're starting/stopping system services.







share|improve this answer














share|improve this answer



share|improve this answer








edited yesterday

























answered yesterday









MintyMinty

34817




34817








  • 1





    You are re-implementing the systemd attributes Requires= and/or BindsTo= and/or After=. Also, the while loop will probably make the CPU fans blow because it re-runs systemctl without any pause.

    – PerlDuck
    yesterday








  • 1





    @perlduck added a 30 second sleep in the else statement to address the inefficiency of running the script continuously. In regards to the former, the asker wanted a cronjob so I figured a simple script would be the most flexible solution, though not the most efficient. Thanks for the pointers.

    – Minty
    yesterday











  • @Minty if this script is called by the cronjob mentioned by the asker, wouldn't this queue a new instance of your script every 5 minutes if the service it is waiting for is not running? If you're already using systemd, you might as well use systemd timer instead of cron and the mechanisms mentioned by PerlDuck for a pure systemd solution.

    – danzel
    21 hours ago














  • 1





    You are re-implementing the systemd attributes Requires= and/or BindsTo= and/or After=. Also, the while loop will probably make the CPU fans blow because it re-runs systemctl without any pause.

    – PerlDuck
    yesterday








  • 1





    @perlduck added a 30 second sleep in the else statement to address the inefficiency of running the script continuously. In regards to the former, the asker wanted a cronjob so I figured a simple script would be the most flexible solution, though not the most efficient. Thanks for the pointers.

    – Minty
    yesterday











  • @Minty if this script is called by the cronjob mentioned by the asker, wouldn't this queue a new instance of your script every 5 minutes if the service it is waiting for is not running? If you're already using systemd, you might as well use systemd timer instead of cron and the mechanisms mentioned by PerlDuck for a pure systemd solution.

    – danzel
    21 hours ago








1




1





You are re-implementing the systemd attributes Requires= and/or BindsTo= and/or After=. Also, the while loop will probably make the CPU fans blow because it re-runs systemctl without any pause.

– PerlDuck
yesterday







You are re-implementing the systemd attributes Requires= and/or BindsTo= and/or After=. Also, the while loop will probably make the CPU fans blow because it re-runs systemctl without any pause.

– PerlDuck
yesterday






1




1





@perlduck added a 30 second sleep in the else statement to address the inefficiency of running the script continuously. In regards to the former, the asker wanted a cronjob so I figured a simple script would be the most flexible solution, though not the most efficient. Thanks for the pointers.

– Minty
yesterday





@perlduck added a 30 second sleep in the else statement to address the inefficiency of running the script continuously. In regards to the former, the asker wanted a cronjob so I figured a simple script would be the most flexible solution, though not the most efficient. Thanks for the pointers.

– Minty
yesterday













@Minty if this script is called by the cronjob mentioned by the asker, wouldn't this queue a new instance of your script every 5 minutes if the service it is waiting for is not running? If you're already using systemd, you might as well use systemd timer instead of cron and the mechanisms mentioned by PerlDuck for a pure systemd solution.

– danzel
21 hours ago





@Minty if this script is called by the cronjob mentioned by the asker, wouldn't this queue a new instance of your script every 5 minutes if the service it is waiting for is not running? If you're already using systemd, you might as well use systemd timer instead of cron and the mechanisms mentioned by PerlDuck for a pure systemd solution.

– danzel
21 hours ago










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