I am trying to execute a python program as a background process inside a container with kubectl as below (kubectl issued on local machine):
kubectl exec -it -- bash -c "cd some-dir && (python xxx.py --arg1 abc &)"
When I login to the container and check "ps -ef" I do not see this process running. Also there is no output from kubectl command itself.
Is the kubectl command issued correct?.
Is there a better way to achieve the same?
How can I see the output/logs printed of the background process being run?
If I need to stop this background process after some duration, what is the best way to do this?
Thanks
Actually, the best way to make this kind of things is adding an entry point to your container and run execute the commands there. Like:
entrypoint.sh:
#!/bin/bash
set -e
cd some-dir && (python xxx.py --arg1 abc &)
./somethingelse.sh
exec "$@"You wouldn't need to go manually inside every single container and run the command.
The nohup Wikipedia page can help; you need to redirect all three IO streams (stdout, stdin and stderr) - an example with yes:
kubectl exec pod -- bash -c "yes > /dev/null 2> /dev/null &" nohup is not required in the above case because I did not allocate a pseudo terminal (no -t flag) and the shell was not interactive (no -i flag) so no HUP signal is sent to the yes process on session termination. See this answer for more details.
Redirecting /dev/null to stdin is not required in the above case since stdin already refers to /dev/null (you can see this by running ls -l /proc/YES_PID/fd in another shell).
To see the output you can instead redirect stdout to a file.
To stop the process you'd need to identity the PID of the process you want to stop (pgrep could be useful for this purpose) and send a fatal signal to it (kill PID for example).
If you want to stop the process after a fixed duration, timeout might be a better option.