Why docker container exits immediately

Question

I run a container in the background using   docker run -d --name hadoop h Service   it exits quickly  But if I run in the foreground  it works fine  I checked logs using  docker logs hadoop   there was no error  Any ideas   DOCKERFILE   FROM java ubuntu new  RUN wget http   archive cloudera com cdh4 one-click-install precise amd64 cdh4-repository 1 0 all deb  RUN dpkg -i cdh4-repository 1 0 all deb  RUN curl -s http   archive cloudera com cdh4 ubuntu precise amd64 cdh archive key   apt-key add -  RUN  apt-get update  RUN apt-get install -y hadoop-0 20-conf-pseudo  RUN dpkg -L hadoop-0 20-conf-pseudo  USER hdfs  RUN hdfs namenode -format  USER root  RUN apt-get install -y sudo  ADD    usr local   RUN chmod 777  usr local start-all sh  CMD    usr local start-all sh     start-all sh      usr bin env bash   etc init d hadoop-hdfs-namenode start   etc init d hadoop-hdfs-datanode start   etc init d hadoop-hdfs-secondarynamenode start   etc init d hadoop-0 20-mapreduce-tasktracker start  sudo -u hdfs hadoop fs -chmod 777     etc init d hadoop-0 20-mapreduce-jobtracker start   bin bash

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If you check Dockerfile from containers  for example fballiano magento2-apache-php  you ll see that at the end of his file he adds the following command  while true  do sleep 1  done  Now  what I recommend  is that you do this  docker container ls --all   grep 127   Then  you will see if your docker image had an error  if it exits with 0  then it probably needs one of these commands that will sleep forever

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I would like to extend or dare I say  improve answer mentioned by camposer  When you run   docker run -dit ubuntu   you are basically running the container in background in interactive mode   When you attach and exit the container by CTRL D  most common way to do it   you stop the container because you just killed the main process which you started your container with the above command   Making advantage of an already running container  I would just fork another process of bash and get a pseudo TTY by running   docker exec -it  lt container ID gt   bin bash

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A docker container exits when its main process finishes    In this case it will exit when your start-all sh script ends  I don t know enough about hadoop to tell you how to do it in this case  but you need to either leave something running in the foreground or use a process manager such as runit or supervisord to run the processes   I think you must be mistaken about it working if you don t specify -d  it should have exactly the same effect  I suspect you launched it with a slightly different command or using -it which will change things   A simple solution may be to add something like   while true  do sleep 1000  done   to the end of the script  I don t like this however  as the script should really be monitoring the processes it kicked off    I should say I stole that code from https   github com sequenceiq hadoop-docker blob master bootstrap sh

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Why docker container exits immediately    If you want to force the image to hang around  in order to debug something or examine state of the file system  you can override the entry point to change it to a shell   docker run -it --entrypoint  bin bash myimagename

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Add this to the end of Dockerfile   CMD tail -f  dev null   Sample Docker file   FROM ubuntu 16 04    other commands  CMD tail -f  dev null   Reference

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My pracitce is in the Dockerfile start a shell which will not exit immediately CMD    sh    -c    service ssh start  bash    then run docker run -dit image name  This way the  ssh  service and container is up running

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whenever I want a container to stay up after finish the script execution I add    amp  amp  tail -f  dev null   at the end of command  So it should be    usr local start-all sh  amp  amp  tail -f  dev null

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You need to run it with -d flag to leave it running as daemon in the background       docker run -d -it ubuntu bash

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Coming from duplicates  I don t see any answer here which addresses the very common antipattern of running your main workload as a background job  and then wondering why Docker exits   In simple terms  if you have  my-main-thing  amp    then either take out the  amp  to run the job in the foreground  or add  wait   at the end of the script to make it wait for all background jobs   It will then still exit if the main workload exits  so maybe run this in a while true loop to force it to restart forever   while true  do     my-main-thing  amp      other things which need to happen while the main workload runs in the background     maybe if you have such things     wait done    Notice also how to write while true  It s common to see silly things like while   true   or while   1   which coincidentally happen to work  but don t mean what the author probably imagined they ought to mean

User · Answer

A nice approach would be to start up your processes and services running them in the background and use the wait  n      command at the end of your script  In bash  the wait command forces the current process to       Wait  for each specified process and return its termination status  If n is not given  all currently  active  child processes  are waited for  and the return status is zero    I got this idea from S  bastien Pujadas  start script for his elk build   Taking from the original question  your start-all sh would look something like this         usr bin env bash   etc init d hadoop-hdfs-namenode start  amp    etc init d hadoop-hdfs-datanode start  amp    etc init d hadoop-hdfs-secondarynamenode start  amp    etc init d hadoop-0 20-mapreduce-tasktracker start  amp   sudo -u hdfs hadoop fs -chmod 777     etc init d hadoop-0 20-mapreduce-jobtracker start  amp   wait

User · Answer

I added read shell statement at the end  This keeps the main process of the container - startup shell script - running

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There are many possible ways to cause a docker to exit immediately  For me  it was the problem with my Dockerfile  There was a bug in that file  I had ENTRYPOINT   dotnet    M4Movie Api dll  instead of ENTRYPOINT   dotnet    M4Movie Api dll    As you can see I had missed one quotation    at the end    To analyze the problem I started my container and quickly attached my container so that I could see what was the exact problem    C  SVenu M4Movie Api Api gt docker start 4ea373efa21b   C  SVenu M4Movie Api Api gt docker attach 4ea373efa21b   Where 4ea373efa21b is my container id  This drives me to the actual issue      After finding the issue  I had to build  restore  publish my container again

User · Answer

Adding   exec        at the end of my shell script was my fix

User · Answer

This did the trick for me   docker run -dit ubuntu   After it  I checked for the processes running using   docker ps -a   For attaching again the container  docker attach CONTAINER NAME   TIP  For exiting without stopping the container type   P Q

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Since the image is a linux  one thing to check is to make sure any shell scripts used in the container have unix line endings  If they have a  M at the end then they are windows line endings   One way to fix them is with dos2unix on  usr local start-all sh to convert them from windows to unix   Running the docker in interactive mode can help figure out other problems   You could have a file name typo or something   see https   en wikipedia org wiki Newline

[docker] Why docker container exits immediately

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