I have several loose containers, including for example a rabbitmq container, that I am using for development. I have started migrating all of these loose containers to a docker-compose file for easier management and spinning up/down when testing. Unfortunately, there is a lot of configuration in these containers that I would rather not have to spend time setting up again.
As such, I was wondering if it was possible to adopt a docker container into a new docker-compose file.
I tried starting the compose file with just using the same name as the loose container, but I get cannot create container for service rabbitmq: Conflict. The container name "/rabbitmq" is already in use by container "<ID>". You have to remove (or rename) that container to be able to reuse that name
If you expect that when you run "docker compose" it will not start a new container if there is one already running with that name and it will just reuse that, it doesn't work that way.
You should define any configurations that you used when running the stand-alone container in your docker-compose file.
Related
Can I update labels on a container using docker-compose without restarting the container?
Ideal scenario:
- change labels in docker-compose.yml
- save docker-compose.yml
- run a command to update the labels without restarting the container
As a general rule, changing the settings or code running inside a container involves deleting and restarting the container. This is totally normal, and docker-compose up will do it for you when necessary. (Remember to make sure any data you care about is stored outside the container.)
At a Docker API level, there are only a limited set of things that can be changed in the Update a container call, and labels aren’t one of those. That means anything that manages a container, whether direct docker commands or Docker Compose, must always delete and recreate a container to change its labels.
I already have a running container for both postgres and redis in use for various things. However, I started those from the command line months ago. Now I'm trying to install a new application and the recipe for this involves writing out a docker compose file which includes both postgres and redis as services.
Can the compose file be modified in such a way as to specify the already-running containers? Postgres already does a fine job of siloing any of the data, and I can't imagine that it would be a problem to reuse the running redis.
Should I even reuse them? It occurs to me that I could run multiple containers for both, and I'm not sure there would be any disadvantage to that (other than a cluttered docker ps output).
When I set container_name to the names of the existing containers, I get what I assume is a rather typical error of:
cb7cb3e78dc50b527f71b71b7842e1a1c". You have to remove (or rename) that container to be able to reuse that name.
Followed by a few that compain that the ports are already in use (5432, 6579, etc).
Other answers here on Stackoverflow suggest that if I had originally invoked these services from another compose file with the exact same details, I could do so here as well and it would reuse them. But the command I used to start them was somehow never written to my bash_history, so I'm not even sure of the details (other than name, ports, and restart always).
Are you looking for docker-compose's external_links keyword?
external_links allows you reuse already running containers.
According to docker-compose specification:
This keyword links to containers started outside this docker-compose.yml or even outside of Compose, especially for containers that provide shared or common services. external_links follow semantics similar to the legacy option links when specifying both the container name and the link alias (CONTAINER:ALIAS).
And here's the syntax:
external_links:
- redis_1
- project_db_1:mysql
- project_db_1:postgresql
You can give name for your container. If there is no container with the given name, then it is the first time to run the image. If the named container is found, restart the container.
In this way, you can reuse the container. Here is my sample script.
containerName="IamContainer"
if docker ps -a --format '{{.Names}}' | grep -Eq "^${containerName}\$"; then
docker restart ${containerName}
else
docker run --name ${containerName} -d hello-world
fi
You probably don't want to keep using a container that you don't know how to create. However, the good news is that you should be able to figure out how you can create your container again by inspecting it with the command
$ docker container inspect ID
This will display all settings, the docker-compose specific ones will be under Config.Labels. For container reuse across projects, you'd be interested in the values of com.docker.compose.project and com.docker.compose.service, so that you can pass them to docker-compose --project-name and use them as the service's name in your docker-compose.yaml.
Im facing the same problem since months now and i dont have an adequate solution.
Im running several Containers based on different images. Some of them were started using portainer with some arguments and volumes. Some of them were started using the CLI and docker start with some arguments and parameters.
Now all these settings are stored somewhere. Because if i stop and retart such a container, everything works well again. but, if i do a commit, backup it with tar and load it on a different system and do a docker start, it has lost all of its settings.
The procedure as described here: https://linuxconfig.org/docker-container-backup-and-recovery does not work in my case.
Now im thinking about to write an own web application which will create me some docker compose files based on my setting rather than to just do a docker start with the correct params. This web application should also take care of the volumes (just folders) and do a incremental backup of them with borg to a remote server.
But actually this is only an idea. Is there a way to "extract" a docker compose file of a running containter? So that i can redeploy a container 1:1 to an other server and just have to run docker run mycontainer and it will have the same settings?
Or do i have to write my web app? Or have i missed some page on google and there is already such a solution?
Thank you!
To see the current configuration of a container, you can use:
docker container inspect $container_id
You can then use those configurations to run your container on another machine. There is no easy import/export of these settings to start another container that I'm aware of.
Most people use a docker-compose.yml to define how they want a container run. They also build images with a Dockerfile and transfer them with a registry server rather than a save/load.
The docker-compose.yml can be used with docker-compose or docker stack deploy and allows the configuration of the container to be documented as a configuration file that is tracked in version control, rather than error prone user entered settings. Running containers by hand or starting them with a GUI is useful for a quick test or debugging, but not for reproducibility.
You would like to backup the instance but the commands you're providing are to backup the image. I'd suggest to update your Dockerfile to solve the issue. In case you really want to go down the saving the instance current status, you should use the docker export and docker import commands.
Reference:
https://docs.docker.com/engine/reference/commandline/import/
https://docs.docker.com/engine/reference/commandline/export/
NOTE: the docker export does not export the content of the volumes anyway, I suggest you to should refer to https://docs.docker.com/engine/admin/volumes/volumes/
I'm confused about common consensus that one shouldn't use data containers. I have specific use case that I want to accomplish.
I want to have docker nginx container and behind it some other container with application. To run newest version of my app I want to download ready container from my private docker registry. The application is for now purely static html, javascript something.
So my plan is to create docker image which will hold the files, and will specify a named volume in some /webapp folder. The nginx container will serve this volume. I do not see any other way how to move bunch of files to remote system the "docker containerized" way. Am I not actually creating cursed data container?
Anyway what happens during app containers exchange? When I stop the app container the volume remains accesible, as it is placed on host. When I pull and start new version of app container. The volume will be created again and prefiled with image files stored at the same location, replacing the content on host so the nginx container will server from now new version of the application.Right? What happens when I will reference volume that does not exist yet from the nginx container.
It seem that named values are not automatically filed with the content of the image. As well I'm not sure how to create named volume in docker file as this syntax taken from here doesn't work
FROM training/webapp
VOLUME webapp:/webapp
I think you might want what i have described here https://stackoverflow.com/a/41576040/3625317
The problem with volumes is, that when a container is recreated, not docker-compose down but rather docker-compose pull + up, the new container will not have your "new code stored in the volume" but rather, due to the recycled volume, still the old anon volume. The point is, you will need a anon-volume for the code anyway, since you want it redeployable, not a named volume since you want the code to be exchangeable.
On re-create the anon-volume is not removed, that said, lets say you have the image:v1 right now and you pull image:v2 and then do a docker-compose up. It will recreate your container based on image:v2 - when this finished, you will have a new container, but the code is still from the old container, which was based on image:v1, since the anon-volume has not been replaced, it was re-assigned. docker-compose down && docker-compose up will resolve that for you - but you have to keep this in mind when dealing with your idea. (down removes anon-volumes)
In general, there is a pro / con, see my other post.
Data-containers in general have a other meaning and have been replaced by so called named volumes. Data-containers have been used to establish a volume-mount which is "named" and not based on a anon-volume.
In the past, you had to create a container with a volume, and later use a container-name based mount of this volume ( the container would be the static / name part ), today, you just create a named volume name and mount by this volume-name, no need for a busybox killed after start based container-name based volume mount.
Is there a way to define all the volume bindings either in the Dockerfile or another configuration file that I am not aware of?
Since volume bindings are used when you create a container, you can't define them in the Dockerfile (which is used to build your Docker image, not the container).
If you want a way to define the volume bindings without having to type them every time, you have the following options:
Create a script that runs the docker command and includes all of the volume options.
If you want to run more than one container, you can also use Docker Compose and define the volume bindings in the docker-compose.yaml file: https://docs.docker.com/compose/compose-file/#/volumes-volumedriver
Out of the two, I prefer Docker Compose, since it includes lots of other cool functionality, e.g. allowing you to define the port bindings, having links between containers, etc. You can do all of that in a script as well, but as soon as you use more than one container at a time for the same application (e.g. a web server container talking to a database container), Docker Compose makes a lot of sense, since you have the configuration in one place, and you can start/stop all of your containers with one single command.