Apache Tomcat 8 not starting within a docker container - apache

Question

I am experimenting with Docker and am very new to it. I am struck at a point for a long time and am not getting a way through and hence came up with this question here...
Problem Statement:
I am trying to create an image from a docker file containing Apache and lynx installation. Once done I am trying to access tomcat on 8080 of the container which is in turn forwarded to the 8082 of the host. But when running the image I never get tomcat started in the container.
The Docker file
FROM ubuntu:16.10
#Install Lynx
Run apt-get update
Run apt-get install -y lynx
#Install Curl
Run apt-get install -y curl
#Install tools: jdk
Run apt-get update
Run apt-get install -y openjdk-8-jdk wget
#Install apache tomcat
Run groupadd tomcat
Run useradd -s /bin/false -g tomcat -d /opt/tomcat tomcat
Run cd /tmp
Run curl -O http://apache.mirrors.ionfish.org/tomcat/tomcat- 8/v8.5.12/bin/apache-tomcat-8.5.12.tar.gz
Run mkdir /opt/tomcat
Run tar xzvf apache-tomcat-8*tar.gz -C /opt/tomcat --strip-components=1
Run cd /opt/tomcat
Run chgrp -R tomcat /opt/tomcat
Run chmod -R g+r /opt/tomcat/conf
Run chmod g+x /opt/tomcat/conf
Run chown -R tomcat /opt/tomcat/webapps /opt/tomcat/work /opt/tomcat/temp opt/tomcat/logs
Run cd /opt/tomcat/bin
Expose 8080
CMD /opt/tomcat/bin/catalina.sh run && tail -f /opt/tomcat/logs/catalina.out
When the image is built I tried running the container by the two below methods
docker run -d -p 8082:8080 imageid tail -f /dev/null
While using the above, container is running but tomcat is not started inside the container and hence not accessible from localhost:8082. Also I do not see anything if I perform docker logs longcontainerid
docker run -d -p 8082:8080 imageid /path/to/catalina.sh start tail -f /dev/null
I see tomcat started when I do docker logs longconatainrid
While using the above the container is started and stopped immediately and is not running as I can see from docker ps and hence again not accessible from localhost:8082.
Can anyone please tell me where I am going wrong?
P.s. I searched a lot on the internet but could not get the thing right. Might be there is some concept that i am not getting clearly.

Answer 1

Looking at the docker run command documentation, the doc states that any command passed to the run will override the original CMD in your Dockerfile:
As the operator (the person running a container from the image), you can override that CMD instruction just by specifying a new COMMAND
1/ Then when you run:
docker run -d -p 8082:8080 imageid tail -f /dev/null
The container is run with COMMAND tail -f /dev/null, the original command starting tomcat is overridden.
To resolve your problem, try to run:
docker run -d -p 8082:8080 imageid
and
docker log -f containerId
To see if tomcat is correctly started.
2/ You should not use the start argument with catalina.sh. Have a look at this official tomcat Dokerfile, the team uses :
CMD ["catalina.sh", "run"]
to start tomcat (when you use start, docker ends container at the end of the shell script and tomcat will start but not maintain a running process).
3/ Finally, why don't you use tomcat official image to build your container? You could just use the :
FROM tomcat:latest
directive at the beginning of your Dockerfile, and add you required elements (new files, webapps war, settings) to the docker image.