docker

Why docker container exits immediately

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
Solution

  • 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)