If I start up a docker container in detached mode using the command:
docker run -d ubuntu
the container immediately exits. docker ps -a yields the output (selected columns shown):
CONTAINER ID IMAGE COMMAND STATUS
245fe871a1e3 ubuntu "/bin/bash" Exited (0) 4 minutes ago
Is it possible to start the same container (container ID 245fe871a1e3) in interactive mode with a terminal session?
I'm afraid there's no such a way to archive this. docker attach and docker exec are working against running container only, but if you docker start the container in your case, it'll exited immediately again because the CMD is /bin/bash.
There's also a discussion about this, post some key info here:
It's not possible to enter a stopped container, because the processes are gone, and therefore, the namespaces are gone as well.
Related
I have a very simple dockerfile with only one row, namely "FROM ubuntu". I created an image from this dockerfile by the command docker build -t ubuntu_ .
I know that I can create a new docker container from this image an run it interactively with the command
docker run -it my_new_container
I can later start this new container with the command
start my_new container
As I understand it, I should also be able to use this container it interactively by
start -i my_new container
But, it does not work. It just runs and exits. I don't get to the container's command prompt as I do when I use run. What am I doing wrong?
If i understood correctly, you want to see the logs from container in terminal, same as when you run the image with docker run. If that's the case, then try with
docker start -a my_docker_container
You can enter a running container with:
docker exec -it <container name> /bin/bash
example:
docker exec -it my_new_container /bin/bash
you can replace bash with sh if bash is not available in the container.
and if you need to explicitly use a UID , like root = UID 0, you can specify this:
docker exec -it -u 0 my_new_container /bin/bash
which will log you as root
Direct answer:
To run an interactive shell for a non-running container, first find the image that the container is based on.
Then:
docker container run -it [yourImage] bash
If your eventual container is based on an alpine image, replace bash with sh.
Technically, this will create a NEW container, but it gets the job done.
EDIT [preferred method]:
An even better way is to give the container something irrelevant to do. A nice solution from the VSCode docs is to put the following command into your service definition of the docker-compose.yml file:
services:
my-app-service:
command: ["sleep", "infinity"]
# other relevant parts of your service def...
The idea here is that you're telling your container to sleep for some time (infinite amount of time). Ironically, this your container will have to maintain this state, forcing the container to keep running.
This is how I run containers. Best wishes to whomever needs this nugget of info. We're all learning :)
You cannot get a shell into a container in its stopped state, or restart it directly with another entry point. If the container keeps exiting and you need to examine it, the only option I know of is to commit the container as a new image and then start a new container with such image, as per a related answer.
If you don't need that container anymore and just want it to stay up, you should run it with a process that will not exit. An example with an Ubuntu image would be (you don't need a Dockerfile for this):
docker run -d ubuntu --name carrot tail -f /dev/null
You will see that this container stays up and you can now run bash on it, to access the CLI:
docker exec -ti carrot bash
If the container has stopped for whatever reason, such as a machine restart, you can bring it back up:
docker start carrot
And it will continue to stay up again.
I would like to restart a docker container, after exiting it and rebooting, with the same runtime with which it was initially created.
Here's what I did so far.
Create the container:
sudo docker run --runtime=nvidia [...]
Restart Docker after exiting the container and rebooting:
service docker restart
Restart the container previously created:
sudo docker start my_container
Reopen the container.
docker exec -it my_container [...]
The program which is then launched in the container doesn't use the Nvidia GPU as expected. It instead uses the system CPU.
Any help would be greatly appreciated.
I got the expected result by creating a new container with the --restart=unless-stopped policy, which lets Docker restart the container by itself when the Docker service is restarted. There seems to be more that's being done in this process than the start/exec sequence that I was using.
I can't start a container on Bluemix with Debian, Centos, Alpine or other. Is there a way or is it blocked?
Image from docker hub.
Is there any getting started for the run command ?
I suppose that i need a file for parameters.
Big difference between running a container in local docker vs in the container service is that all containers in the container service are effectively running -d (i.e. daemon/disconncted mode). If you're just using the base images you listed, most of those do not have a long running process in the container, and expect that you will be running it interactive.
Result of that is that in the container service, the container starts, then exits again because it's non-interactive, and there's no other process to keep it alive. You can try adding a wait as the "cmd" for it.
i.e. for your dockerfile:
FROM alpine
build that to your registry, then run with something like cf ic run --name alpinetest -m 512 registry.ng.bluemix.net/yourregistryhere/alpine sh -c "sleep 1000000"
Then, to get an interactive shell, you can exec into the container using cf ic exec -ti alpinetest /bin/sh
Obviously, to have it do something useful, you're probably going to want to put an actual server running in there as the foreground app, and set that as the CMD or ENTRYPOINT, but that'll give you access to it running to poke at.
I'm using below command to run docker,
docker run -it centos:6.5 bash
It starts bash with root user, no problem.
But I wish to have multiple terminals to connect to it and do different things. I found attach command will only duplicate a terminal window which all input/output will be propagated. It doesn't solve my requirement.
How to do this?
Once the container is running, you should be able to use docker exec to run an additional Bash session in the same container.
When your first container is running, use docker ps to find its Container ID (the first column in the docker ps output), e.g. 4a7afcdeb729, then run the following:
docker exec -it 4a7afcdeb729 bash
This should open a new terminal session in the container.
I'm doing some initial tests with docker. At moment i have my images and I can put some containers running, with:
docker ps
I do docker attach container_id and start apache2 service.
Then from the main console I commit the container to the image.
After exiting the container, if I try to start the container or try to run one new container from the committed image, the service is always stopped.
How can create or restart one container with the services started, for example apache?
EDIT:
I've learned a lot about Docker since originally posting this answer. "Starting services automatically in Docker containers" is not a good usage pattern for Docker. Instead, use something like fleet, Kubernetes, or even Monit/SystemD/Upstart/Init.d/Cron to automatically start services that execute inside Docker containers.
ORIGINAL ANSWER:
If you are starting the container with the command /bin/bash, then you can accomplish this in the manner outlined here: https://stackoverflow.com/a/19872810/2971199
So, if you are starting the container with docker run -i -t IMAGE /bin/bash and if you want to automatically start apache2 when the container is started, edit /etc/bash.bashrc in the container and add /usr/local/apache2/bin/apachectl -f /usr/local/apache2/conf/httpd.conf (or whatever your apache2 start command is) to a newline at the end of the file.
Save the changes to your image and restart it with docker run -i -t IMAGE /bin/bash and you will find apache2 running when you attach.
An option that you could use would to be use a process manager such as Supervisord to run multiple processes. Someone accomplished this with sshd and mongodb: https://github.com/justone/docker-mongodb
I guess you can't. What you can do is create an image using a Dockerfile and define a CMD in that, which will be executed when the container starts. See the builder documentation for the basics (https://docs.docker.com/reference/builder/) and see Run a service automatically in a docker container for information on keeping your service running.
You don't need to automate this using a Dockerfile. You could also create the image via a manual commit as you do, and run it command line. Then, you supply the command it should run (which is exactly what the Dockerfile CMD actually does). You can also override the Dockerfiles CMD in this way: only the latest CMD will be executed, which is the command line command if you start the container using one. The basic docker run -i -t base /bin/bash command from the documentation is an example. If your command becomes too long you could create a convenience script of course.
By design, containers started in detached mode exit when the root process used to run the container exits.
You need to start a Apache service in FOREGROUND mode.
docker run -p 8080:80 -d ubuntu/apache apachectl -D FOREGROUND
Reference: https://docs.docker.com/engine/reference/run/#detached-vs-foreground
Try to add start script to entrypoint in dockerfile like this;
ENTRYPOINT service apache2 restart && bash