Why docker exec is killing nohup process on exit?

Question

I have running docker ubuntu container with just a bash script inside. I want to start my application inside that container with docker exec like that:

docker exec -it 0b3fc9dd35f2 ./main.sh

Inside main script I want to run another application with nohup as this is a long running application:

#!/bin/bash
nohup ./java.sh &
#with this strange sleep the script is working
#sleep 1
echo `date` finish main >> /status.log

The java.sh script is as follow (for simplicity it is a dummy script):

#!/bin/bash
sleep 10
echo `date` finish java >> /status.log

The problem is that java.sh is killed immediately after docker exec returns. The question is why?

The only solution I found out is to add some dummy sleep 1 into the first script after nohup is started. Than second process is running fine. Do you have any ideas why it is like that?

[EDIT]

Second solution is to add some echo or trap command to java.sh script just before sleep. Than it works fine. Unfortunately I cannot use this workaround as instead of this script I have java process.

Answer 1

Okay, let's join two answers above :D

First rcmgleite say exactly right: use

-d

options to run process as 'detached' background.

And second (the most important!) if you run detached process, you don't needed nohup!

deploy_app.sh

#!/bin/bash
cd /opt/git/app
git pull
python3 setup.py install
python3 -u webui.py >> nohup.out

Execute this inside a container

docker exec -itd container_name bash -c "/opt/scripts/deploy_app.sh"

Check it

$ docker attach container_name
$ ps aux
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.0  11768  1940 pts/0    Ss   Aug31   0:00 /bin/bash
root       887  0.4  0.0  11632  1396 pts/1    Ss+  02:47   0:00 /bin/bash /opt/scripts/deploy_app
root       932 31.6  0.4 235288 32332 pts/1    Sl+  02:47   0:00 python3 -u webui.py