Executing a shell script within docker with RUN command

Question

New to dockers, so please bear with me.

My Dockerfile contains an ENTRYPOINT:

ENV MONGOD_START "mongod --fork --logpath /var/log/mongodb.log --logappend --smallfiles"
ENTRYPOINT ["/bin/sh", "-c", "$MONGOD_START"]

I have a shell script add an entry to database through python script, and starts the server.

The script startApp.sh

chmod +x /addAddress.py
python /addAddress.py $1
cd /myapp/webapp 
grunt serve --force

Now, all the below RUN commands are unsuccessful in executing this script.

sudo docker run -it --privileged myApp -C /bin/bash && /myApp/webapp/startApp.sh loc

sudo docker run -it --privileged myApp /myApp/webapp/startApp.sh loc

The docker log of container is

"about to fork child process, waiting until server is ready for connections. forked process: 7 child process started successfully, parent exiting "

Also, the startApp.sh executes fine when I open a bash prompt in docker and run it.

I am unable to figure out what wrong I am doing, help please.

What's the output of docker logs <container> ? Have you tried launching the container with just bash instead of startApp.sh and then executing startApp.sh from your bash prompt? — Frank Schmitt
– Frank Schmitt, Commented Mar 8, 2016 at 20:14
sudo docker ps doesn't show this as a running container. So can't fetch the logs. When trying to launch a bash and executing startApp.sh it runs fine and gives me the expected output. — swateek
– swateek, Commented Mar 8, 2016 at 20:15
Okay, the container which exited without any further response has the following log - "about to fork child process, waiting until server is ready for connections. forked process: 7 child process started successfully, parent exiting " — swateek
– swateek, Commented Mar 8, 2016 at 20:17
Please don't post additional info in comments; add this info to the question by edit ing it instead. — Frank Schmitt
– Frank Schmitt, Commented Mar 8, 2016 at 20:24
Thank you for pointing that out Frank, I have updated the question. — swateek
– swateek, Commented Mar 8, 2016 at 20:27

Raghwendra Singh · Accepted Answer · 2017-08-28 11:20:06Z

I would suggest you to create an entrypoint.sh file:

#!/bin/sh

# Initialize start DB command
# Pick from env variable MONGOD_START if it exists
# else use the default value provided in quotes
START_DB=${MONGOD_START:-"mongod --fork --logpath /var/log/mongodb.log --logappend --smallfiles"}

# This will start your DB in background
${START_DB} &

# Go to startApp directory and execute commands
`chmod +x /addAddress.py;python /addAddress.py $1; \
               cd /myapp/webapp ;grunt serve --force`

Then modify your Dockerfile by removing the last line and replacing it with following 3 lines:

COPY entrypoint.sh /

RUN chmod +x /entrypoint.sh

ENTRYPOINT ["/entrypoint.sh"]

Then rebuild your container image using

docker build -t NAME:TAG .

Now you run following command to verify if ENTRYPOINT is /entrypoint.sh

docker inspect NAME:TAG | less

Frank Schmitt · Accepted Answer · 2016-03-08 20:48:06Z

0

I guess (and I might be wrong, since I'm neither a MongoDB nor a Docker expert) that your combination of mongod --fork and /bin/sh -c is the culprit.

What you're essentially executing is this:

/bin/sh -c mongod --fork ...

which

executes a shell
this shell executes a single command and waits for it to finish
this command launches MongoDB in daemon mode
MongoDB forks and immediately exits

The easiest fix is probably to just use

 CMD ["mongod"]

like the official MongoDB Docker does.

answered Mar 8, 2016 at 20:48

Frank Schmitt

30.5k13 gold badges79 silver badges111 bronze badges

2 Comments

swateek Over a year ago

Frank, I need the --fork because while building the docker. There are certain initial data that I need to populate into MongoDB. It has to run in a separate shell.

swateek Over a year ago

I tried your approach too, without using fork. It doesn't even complete execution of the mongod and thus never reaches the script.

Collectives™ on Stack Overflow

Executing a shell script within docker with RUN command

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related