How to keep Docker container running after starting services

Question

I ve seen a bunch of tutorials that seem do the same thing I m trying to do  but for some reason my Docker containers exit  Basically  I m setting up a web-server and a few daemons inside a Docker container  I do the final parts of this through a bash script called run-all sh that I run through CMD in my Dockerfile  run-all sh looks like this   service supervisor start service nginx start   And I start it inside of my Dockerfile as follows   CMD   sh     root credentialize and run sh     I can see that the services all start up correctly when I run things manually  i e  getting on to the image with -i -t  bin bash   and everything looks like it runs correctly when I run the image  but it exits once it finishes starting up my processes  I d like the processes to run indefinitely  and as far as I understand  the container has to keep running for this to happen  Nevertheless  when I run docker ps -a  I see      docker test  docker ps -a CONTAINER ID        IMAGE                            COMMAND                CREATED             STATUS                      PORTS               NAMES c7706edc4189        some name some repo blah    sh  root run-all sh   8 minutes ago       Exited  0  8 minutes ago                        grave jones   What gives  Why is it exiting  I know I could just put a while loop at the end of my bash script to keep it up  but what s the right way to keep it from exiting

User · Accepted Answer

This is not really how you should design your Docker containers.

When designing a Docker container, you're supposed to build it such that there is only one process running (i.e. you should have one container for Nginx, and one for supervisord or the app it's running); additionally, that process should run in the foreground.

The container will "exit" when the process itself exits (in your case, that process is your bash script).

However, if you really need (or want) to run multiple service in your Docker container, consider starting from "Docker Base Image", which uses runit as a pseudo-init process (runit will stay online while Nginx and Supervisor run), which will stay in the foreground while your other processes do their thing.

They have substantial docs, so you should be able to achieve what you're trying to do reasonably easily.

User · Answer

I just had the same problem and I found out that if you are running your container with the -t and -d flag  it keeps running   docker run -td  lt image gt    Here is what the flags do  according to docker run --help    -d  --detach false         Run container in background and print container ID -t  --tty false            Allocate a pseudo-TTY   The most important one is the -t flag  -d just lets you run the container in the background

User · Answer

Make sure that you add daemon off  to you nginx conf or run it with CMD   nginx    -g    daemon off    as per the official nginx image  Then use the following to run both supervisor as service and nginx as foreground process that will prevent the container from exiting  service supervisor start  amp  amp  nginx  In some cases you will need to have more than one process in your container  so forcing the container to have exactly one process won t work and can create more problems in deployment   So you need to understand the trade-offs and make your decision accordingly

User · Answer

There are some cases during development when there is no service yet but you want to simulate it and keep the container alive  It is very easy to write a bash placeholder that simulates a running service  while true  do   sleep 100 done  You replace this by something more serious as the development progress

User · Answer

you can run plain cat without any arguments as mentioned by bro  Sa ad to simply keep the container working  actually doing nothing but waiting for user input   Jenkins  Docker plugin does the same thing

User · Answer

The reason it exits is because the shell script is run first as PID 1 and when that s complete  PID 1 is gone  and docker only runs while PID 1 is   You can use supervisor to do everything  if run with the  -n  flag it s told not to daemonize  so it will stay as the first process   CMD    usr bin supervisord    -n     And your supervisord conf    supervisord  nodaemon true   program startup  priority 1 command  root credentialize and run sh stdout logfile  var log supervisor   program name s log stderr logfile  var log supervisor   program name s log autorestart false startsecs 0   program nginx  priority 10 command nginx -g  daemon off   stdout logfile  var log supervisor nginx log stderr logfile  var log supervisor nginx log autorestart true   Then you can have as many other processes as you want and supervisor will handle the restarting of them if needed   That way you could use supervisord in cases where you might need nginx and php5-fpm and it doesn t make much sense to have them apart

User · Answer

How about using the supervise form of service if available   service YOUR SERVICE supervise     Once supervise is successfully running  it will not exit unless it is   killed or specifically asked to exit    Saves having to create a supervisord conf

User · Answer

Along with having something along the lines of   ENTRYPOINT   quot tail quot    quot -f quot    quot  dev null quot   in your docker file  you should also run the docker container with -td option  This is particularly useful when the container runs on a remote m c  Think of it more like you have ssh ed into a remote m c having the image and started the container  In this case  when you exit the ssh session  the container will get killed unless it s started with -td option  Sample command for running your image would be  docker run -td  lt any other additional options gt   lt image name gt  This holds good for docker version 20 10 2

User · Answer

Motivation   There is nothing wrong in running multiple processes inside of a docker container  If one likes to use docker as a light weight VM - so be it  Others like to split their applications into micro services  Me thinks  A LAMP stack in one container  Just great    The answer   Stick with a good base image like the phusion base image  There may be others  Please comment   And this is yet just another plead for supervisor  Because the phusion base image is providing supervisor besides of some other things like cron and locale setup  Stuff you like to have setup when running such a light weight VM  For what it s worth it also provides ssh connections into the container   The phusion image itself will just start and keep running if you issue this basic docker run statement   moin stretchDEV    docker run -d phusion baseimage 521e8a12f6ff844fb142d0e2587ed33cdc82b70aa64cce07ed6c0226d857b367 moin stretchDEV    docker ps CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS 521e8a12f6ff        phusion baseimage     sbin my init      12 seconds ago      Up 11 seconds   Or dead simple   If a base image is not for you    For the quick CMD to keep it running I would suppose something like this for bash   CMD exec  bin bash -c  trap   TERM INT  sleep infinity  amp  wait    Or this for busybox   CMD exec  bin sh -c  trap   TERM INT   while true  do sleep 1000  done   amp  wait    This is nice  because it will exit immediately on a docker stop  Just plain sleep or cat will take a few seconds before the container exits

User · Answer

Capture the PID of the ngnix process in a variable  for example  NGNIX PID  and at the end of the entrypoint file do  wait  NGNIX PID    In that way  your container should run until ngnix is alive  when ngnix stops  the container stops as well

User · Answer

If you are using a Dockerfile  try   ENTRYPOINT   tail    -f     dev null      Obviously this is for dev purposes only  you shouldn t need to keep a container alive unless it s running a process eg  nginx

[docker] How to keep Docker container running after starting services?

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