I've made a Docker image for my spring boot application. I'm unable to run systemctl command inside the Docker container. This is what I get when I execute
systemctl daemon reload :-
Failed to connect to bus: No such file or directory
Steps I followed to build the Docker image :-
1) docker build --rm -t <IMAGE_NAME> .
2) docker-compose up
3) docker exec -it <CONTAINER_NAME> bash
When I start a service using :-
service <SERVICE_NAME> start
I get unrecognised service. How do I execute a service inside docker?
If you want to reuse your existing systemd service descriptors then you either need to run systemd as the entrypoint, or you can use a wrapper script like the docker-systemctl-replacement which is both a service manager and an init daemon.
As David commented, you generally don't use process managers like systemctl in a docker environment. Instead, you can make your application the primary entry point of the image. See more in the Spring documentation about using it with docker at https://spring.io/guides/gs/spring-boot-docker/#_containerize_it.
Key is having something like this in your dockerfile, instead of systemctl daemon reload
ENTRYPOINT ["java","-jar","/app.jar"]
Related
I'm building an app that makes api calls to run code inside docker containers
I want to run a docker container that has docker running inside it.
I want to create a docker file that pulls other docker images inside it and then waits for api calls (on port 2376) to create, run and delete containers based on the docker images that i pulled into the dockerfile
This is the dockerfile I'm trying to create right now.
FROM docker:stable
RUN docker pull python
EXPOSE 23788
CMD tail -f /dev/null
However when the RUN command is issued i get this error message:
docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
I don't really know how to start docker inside a docker container.
The reason i need this kind of a docker file is so that i can then use kubernetes to scale this part of my application
There's a special image for this, docker:dind. See the bit about "Docker in Docker" in https://hub.docker.com/_/docker.
I use following command to build web server
docker run --name webapp -p 8080:4000 mypyweb
When it stopped and I want to restart, I always use:
sudo docker start webapp && sudo docker exec -it webapp bash
But I can't see the server state as the first time:
Digest: sha256:e61b45be29f72fb119ec9f10ca660c3c54c6748cb0e02a412119fae3c8364ecd
Status: Downloaded newer image for ericgoebelbecker/stackify-tutorial:1.00
* Running on http://0.0.0.0:4000/ (Press CTRL+C to quit)
How can I see the state instead of interacting with the shell?
When you use docker run, the default behavior is to run the container detached. This runs in the background and is detached from your shell's stdin/out.
To run the container in the foreground and connected to stdin/out:
docker run --interactive --tty --publish=8080:4000 mypyweb
To docker start a container, similarly:
docker start --interactive --attach [CONTAINER]
NB --attach rather than -tty
You may list (all add --all) running containers:
docker container ls
E.g. I ran Nginx:
CONTAINER ID IMAGE PORTS NAMES
7cc4b4e1cfd6 nginx 0.0.0.0:8888->80/tcp nostalgic_thompson
NB You may use the NAME or any uniquely identifiable subset of the ID to reference the container
Then:
docker stop nostalgic_thompson
docker start --interative --attach 7cc4
You may check the container's logs (when running detached or from another shell) by grabbing the container's ID or NAMES
docker logs nostalgic_thompson
docker logs 7cc4
HTH!
Using docker exec is causing the shell to attach to the container. If you are comparing the behavior of docker run versus docker start, they behave differently, and it is confusing. Try this:
$ sudo docker start -a webapp
the -a flag tells docker to attach stdout/stderr and forward signals.
There are some other switches you can use with the start command (and a huge number for the run command). You can run docker [command] --help to get a summary of the options.
One other command that you might want to use is logs which will show the console output logs for a running container:
$ docker ps
[find the container ID]
$ docker logs [container ID]
If you think your container's misbehaving, it's often not wrong to just delete it and create a new one.
docker rm webapp
docker run --name webapp -p 8080:4000 mypyweb
Containers occasionally have more involved startup sequences and these can assume they're generally starting from a clean slate. It should also be extremely routine to delete and recreate a container; it's required for some basic tasks like upgrading the image underneath a container to a newer version or changing published ports or environment variables.
docker exec probably shouldn't be part of your core workflow, any more than you'd open a shell to interact with your Web browser. I generally don't tend to docker stop containers, except to immediately docker rm them.
when i am using the CMD parameter, docker build is success.
But To run the docker container, container is existing immediately.
Try to read about docker & how it works after container is started.
More about how to read logs of container: https://docs.docker.com/engine/reference/commandline/logs/
I want to run an image which I have already created and uploaded on the docker hub. Is it possible to run that image on lxc/lxd? Basically I want to do performance comparison between docker and lxc.
I have installed skopeo, umoci, go-md2man and jq.
Now, when I try to run the command lxc-create c1 -t oci – --url docker://awaisaz/test:part2
it gives trust policy error. /etc/containers/policy.json not such file or directory
Can anyone suggest me a solution or alternate way to do this?
So, you want to run a docker container inside an LXC Container.
firstly, you need to make docker process up and running inside an lxc container.
sudo lxc config edit <lxc-container-name>
In Config Object, Add
linux.kernel_modules: overlay,ip_tables
security.nesting: true
security.privileged: true
Then Exit from that YAML File, And Restart the LXC Container
sudo lxc restart <container_name>
After Successfull restart of LXC Container.
exec into that container by
sudo lxc exec <container_name> /bin/bash
Then,
sudo rm /var/lib/docker/network/files/local-kv.db
Restart Docker Service,
service docker restart (In LXC Container)
Then you can use docker process in LXC Container as if you are in a VM.
I'm trying to run Docker inside a Jenkins container that is also running in Docker (i.e. Docker in Docker). What I want to know is how to properly start the Docker service when booting Jenkins. The only solution I've found today is to build my own Jenkins image based on the official Jenkins image but change the jenkins script loaded by the entry point to also start up Docker:
# I've added this line just before Jenkins is started from the script:
sudo service docker start
# I've also removed "exec" from the original file which used "exec java $JAVA_TOPS ..." but that didn't work
java $JAVA_OPTS -jar /usr/share/jenkins/jenkins.war $JENKINS_OPTS "$#"
This works when I run (using docker run) a new container but the problem is that if I do (docker start) on stopped container the Docker service is not started.
I strongly suspect that this is not the right way to start my Docker service. My plan is to perhaps use supervisord to start Jenkins and Docker separately (I suppose container linking is out of the question since Docker should be executed as a service on the same container that Jenkins is running on?). My concern with this approach is that I'm going to lose the EntryPoint specified in the Jenkins Dockerfile which allows me to pass arguments to the Jenkins container when starting the container, for example:
docker run -p 8080:8080 -v /your/home:/var/jenkins_home jenkins -- <jenkins_arguments>
Does anyone have any recommendations on a good way to solve this preferably by not forking the official Jenkins image?
I'm pretty you cannot do that.
Docker in Docker doesn't mean you have to run docker inside docker with 3 level : host > First level container > Second Level Container
In fact, you just need to share docker with host, and this is your host who will run others containers.
To do that, you have to mount volume with -v parameter
-v /var/run/docker.sock:/var/run/docker.sock
with this command, when you will docker run inside you jenkins container, the docker client will communicate with docker deamon from your host in order to run new container.
To do that, you should run your jenkins container with privileged
--privileged
To resume, here is the full command line
docker run -d -v /var/run/docker.sock:/var/run/docker.sock --privileged myimage
And you you don't need to create a new jenkins image for that.
Hoping to have helped you
http://container-solutions.com/running-docker-in-jenkins-in-docker/