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
This question is related to
docker
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 <container ID> /bin/bash
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
You need to run it with -d flag to leave it running as daemon in the background.
docker run -d -it ubuntu bash
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
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 &
then either take out the &
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 &
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.)
whenever I want a container to stay up after finish the script execution I add
&& tail -f /dev/null
at the end of command. So it should be:
/usr/local/start-all.sh && tail -f /dev/null
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.
Adding
exec "$@"
at the end of my shell script was my fix!
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.
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
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>docker start 4ea373efa21b
C:\SVenu\M4Movie\Api\Api>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.
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 Sébastien 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 &
/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 &
wait
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
I added read
shell statement at the end. This keeps the main process of the container - startup shell script - running.
Source: Stackoverflow.com