I am looking for a way to destroy a single shot container after exiting with success (0).
The docker cloud has an option called "autodestroy". Is there anything like that for Docker Swarm?
Update
I would like to autoremove a successfully exited container in a Docker Swarm by adding "special information" to the compose file.
Sorry, but no, that feature does not exist. If you were more descriptive about what you're looking to do, we might provide a better answer :)
Related
I am learning docker and during my project, i can't enter the mongo db with this command:
mongo -u "username" -p "mypassword"
It throws me this error:
bash: mongo: command not found
I am not sure what the issue is. I have installed the community edition of mongo db and i also tried different terminals but i can't enter the db.
Any suggestions?
Thanks in advance!
I assume, you did the following: Create docker-compose.yml as you wrote before. Start docker compose up. This will start a container on your system, having mongodb installed in it. It will not affect your "normal" system outside this container. (You can imagine it as kind of a virtual machine, though it is not really the same.) So, if you did not install mongodb on your local host system as well, the error you encounter is quite explicable.
If you want to access the mongodb running within the container, you have two possibilities:
1. From outside the container (which is the more common use case)
You will have to install mongo on your regular PC (or anywhere you want to access your db from) as well. Then you would issue mongo 127.0.0.1:3000. The 3000 is important as your docker-compose.yml says, mongo is listening on port 3000. Note that you might have to get your network configuration adapted before this works, especially from other PCs, where 127.0.0.1 won't be correct.
2. From within the container
Once your container is started, you can also execute a command inside it, like this: docker exec -it ${container_id} /bin/bash. You'll have to find out the container's ID beforehand, using something like docker-compose ps -q. This will start a bash shell inside the container and "connect" you to it. (If there's no /bin/bash installed in the container, this will not work. Try e. g. /bin/sh instead.) Now your terminal will be inside the container and just be able to use the commands present there. So, to get back to your local PC, don't forget to issue exit.
Conclusion
IMHO, the crucial point is, that the physical PC you are working in front of and the container running inside it are almost completely different systems, connected only by the docker daemon and some virtual network access. You'll have to keep that in mind and decide what you want to do/run inside the container and what to do outside, on the host.
Here is a little further reference that might help you. And this answer is about how to find out your container ID in an automated way. (Assuming that you are running just that one container!)
Is it necessary to use "docker-compose down" before "docker-compose up". I dont want my application go down. I am using docker-compose at this point of time and having no plan to move to kubernetes etc.
If we remove "docker-compose down" then how it will handle the orphan-volumes and images?
Any pointer is highly appreciated.
Thanks,
Sanjiv
No, you don't necessarily have to use docker-compose down before a docker-compose up. If you use docker-compose up on a running service stack, docker-compose will just recreate the services that have been changed. Changed either through:
a changed docker-compose.yml, or
updated images (either because you pulled new images, or rebuild them yourself).
To remove orphaned volumes, you have to issue a special flag --remove-orphans , see docker-compose up. But that behavior is the same with docker-compose down.
Also images are not changed with neither command. The difference is that with docker-compose down & docker-compose up, all running containers are removed and recreated from their images. So in case data was written inside the container, that data will be lost.
I'm new to docker. You can take a look at my last questions here and see that I've been asking questions down this line. I read the docs carefully, and also read several articles on the web (which is pretty difficult given the rapid versioning in docker), but I still can't get a clear picture of how am I supposed to use containers and its impact on persistance.
The official postgres image creates a volume in its Dockerfile using this command
VOLUME /var/lib/postgresql/data
And the readme.md file shows only one example of how to run the image
docker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d postgres
When I try that, I can see (with "docker inspect some-postgres") that the volume created lives in a random directory in my host, and it seems to "belong" to that particular container.
So here are some questions that may help my understanding:
It looks (from the official postgres image docs) that expected usage is to use "docker run" to create the container, and "docker start" afterwards (this last bit I inferred from the fact that -d and --name are used). This makes sense to me, but conflicts with a lot of information I've seen regarding containers should be ephemeral. If spin a new container every time, then the default VOLUME config in the Dockerfile doesn't work for persistance. What's the right way of doing things?
Given the above is correct (that I can run once and start many times), the only reason I see for the VOLUME command in the Dockerfile is I/O performance because of the CoW filesystem bypass. Is this right?
Could you please clearly explain what's wrong with using this approach over the (I think unofficially) recommended way of using a data container? I'd like to know the pros/cons to my specific situation, which is a node js intranet application.
Thanks,
Awer
You're correct that you can start the container using 'docker run' and start it again in the future using 'docker start' assuming you haven't removed the container. You're also correct that docker containers are supposed to be ephemeral and you shouldn't be in bad shape if the container disappears. What you can do is mount a volume into the docker container to the storage location of the database.
docker run -v /postgres/storage:/container/postgres --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d postgres
If you know the location of where the database writes to inside the container you can mount it correctly and then even if you remove the postgres container, when you start back up all your data will persist. You may need to mount some other areas that control configurations as well unless you modify and save the container.
I'm new to docker. I'm still trying to wrap my head around all this.
I'm building a node application (REST api), using Postgresql to store my data.
I've spent a few days learning about docker, but I'm not sure whether I'm doing things the way I'm supposed to.
So here are my questions:
I'm using the official docker postgres 9.5 image as base to build my own (my Dockerfile only adds plpython on top of it, and installs a custom python module for use within plpython stored procedures). I created my container as suggedsted by the postgres image docs:
docker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d postgres
After I stop the container I cannot run it again using the above command, because the container already exists. So I start it using docker start instead of docker run. Is this the normal way to do things? I will generally use docker run the first time and docker start every other time?
Persistance: I created a database and populated it on the running container. I did this using pgadmin3 to connect. I can stop and start the container and the data is persisted, although I'm not sure why or how is this happening. I can see in the Dockerfile of the official postgres image that a volume is created (VOLUME /var/lib/postgresql/data), but I'm not sure that's the reason persistance is working. Could you please briefly explain (or point to an explanation) about how this all works?
Architecture: from what I read, it seems that the most appropriate architecture for this kind of app would be to run 3 separate containers. One for the database, one for persisting the database data, and one for the node app. Is this a good way to do it? How does using a data container improve things? AFAIK my current setup is working ok without one.
Is there anything else I should pay atention to?
Thanks
EDIT: adding to my confusion, I just ran a new container from the debian official image (no Dockerfile, just docker run -i -t -d --name debtest debian /bin/bash). With the container running in the background, I attached to it using docker attach debtest and the proceeded to apt-get install postgresql. Once installed I ran (still from within the container) psql and created a table in the default postgres database, and populated it with 1 record. Then I exited the shell and the container stopped automatically since the shell wasn't running anymore. I started the container againg using docker start debtest, then attached to it and finally run psql again. I found everything is persisted since the first run. Postgresql is installed, my table is there, and offcourse the record I inserted is there too. I'm really confused as to why do I need a VOLUME to persist data, since this quick test didn't use one and everything apears to work just fine. Am I missing something here?
Thanks again
1.
docker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword
-d postgres
After I stop the container I cannot run it again using the above
command, because the container already exists.
Correct. You named it (--name some-postgres) hence before starting a new one, the old one has to be deleted, e.g. docker rm -f some-postgres
So I start it using
docker start instead of docker run. Is this the normal way to do
things? I will generally use docker run the first time and docker
start every other time?
No, it is by no means normal for docker. Docker process containers are supposed normally to be ephemeral, that is easily thrown away and started anew.
Persistance: ... I can stop and start
the container and the data is persisted, although I'm not sure why or
how is this happening. ...
That's because you are reusing the same container. Remove the container and the data is gone.
Architecture: from what I read, it seems that the most appropriate
architecture for this kind of app would be to run 3 separate
containers. One for the database, one for persisting the database
data, and one for the node app. Is this a good way to do it? How does
using a data container improve things? AFAIK my current setup is
working ok without one.
Yes, this is the good way to go by having separate containers for separate concerns. This comes in handy in many cases, say when for example you need to upgrade the postgres base image without losing your data (that's in particular where the data container starts to play its role).
Is there anything else I should pay atention to?
When acquainted with the docker basics, you may take a look at Docker compose or similar tools that will help you to run multicontainer applications easier.
Short and simple:
What you get from the official postgres image is a ready-to-go postgres installation along with some gimmicks which can be configured through environment variables. With docker run you create a container. The container lifecycle commands are docker start/stop/restart/rm Yes, this is the Docker way of things.
Everything inside a volume is persisted. Every container can have an arbitrary number of volumes. Volumes are directories either defined inside the Dockerfile, the parent Dockerfile or via the command docker run ... -v /yourdirectoryA -v /yourdirectoryB .... Everything outside volumes is lost with docker rm. Everything including volumes is lost with docker rm -v
It's easier to show than to explain. See this readme with Docker commands on Github, read how I use the official PostgreSQL image for Jira and also add NGINX to the mix: Jira with Docker PostgreSQL. Also a data container is a cheap trick to being able to remove, rebuild and renew the container without having to move the persisted data.
Congratulations, you have managed to grasp the basics! Keep it on! Try docker-compose to better manage those nasty docker run ...-commands and being able to manage multi-containers and data-containers.
Note: You need a blocking thread in order to keep a container running! Either this command must be explicitly set inside the Dockerfile, see CMD, or given at the end of the docker run -d ... /usr/bin/myexamplecommand command. If your command is NON blocking, e.g. /bin/bash, then the container will always stop immediately after executing the command.
I'd like to make the deployment to production the easiest it can be, but struggling with the way how to do it.
If I will have docker for production, it will be nice to have docker image with my application deployables, but I'm not sure if it is good approach.
I have several concerns:
wouldn't the layer system bloat, when I will replace the file every time in new version of image?
Is it good idea to make DB scripts and migration tool part of this image?
The last concern is how to run it conveniently. I don't want to go there stop the tomcat container and start it again using volume from new application image(as the new app container name cannot be the same).
I have seen ways to do that, but I don't like them very much i.e. deploy to Tomcat docker image ,create Tomcat image with application already bundled or use host system volume. I like to have something like install "CD". I'd like to evaluate my idea with other approaches, speaking about the proper tool to run it is maybe for other question.
wouldn't the layer system bloat, when I will replace the file every time in new version of image?
No because you can clean up dangling images
docker rmi $(docker images --filter "dangling=true" -q --no-trunc)
Is it good idea to make DB scripts and migration tool part of this image?
Yes, if your startup script knows to detect if it needs to apply them.
I don't like them very much i.e. deploy to Tomcat docker image ,create Tomcat image with application already bundled or use host system volume.
If your data volume container is separate from the app, that shouldn't be an issue.
From the discussion, the OP adds:
using this docker create --name <container_name> <image_name> with different image name can retain the container name and I can run Tomcat container with the same volumes-from?
docker run -it --rm -p 8888:8080 --volumes-from <container_name> <image_name>
That is the idea, but it won't work if there is already a create data container with that name.
If there is no persistent data in it, one can docker rm that data container, and recreate it with the same name.
If there are persistent data, then it is best to copy the new updated data through an intermediate (docker run) container which would mount temporarily the data container.