Add VOLUME to Dockerfile

[freemountain]

Please add VOLUME /data into the Dockerfile.
So you could use --volumes-from to link containers.

Thank you in advance

[unknwon]

Thanks your feedback!

But I think this is basically same as #1631 and please read the docs here: https://github.com/gogits/gogs/tree/master/docker

[freemountain]

Thank your for the quick response.
I read the docs but i didnt see the other issue.
The docs describe how to mount a host directory as a data volume.
This is possible but i think using data volume containers is a better (and more 'dockerish') approach.
Adding VOLUME /data doesent prevent someone from adding other volumes using the -vflag.

[unknwon]

Adding VOLUME /data doesent prevent someone from adding other volumes using the -vflag.

But why would you need two volumes for same purpose, as explained in #1631, the Dockerfile tries to leave open choices for volume.

[freemountain]

I just wanted to clarify, that even if you add the volume directive to the dockerfile, you leave open choices for volumes.
It is a way to tell docker where you need persistence in your container, so you could use --volumes-fromlike this:

docker run --name=gogs-data --entrypoint /bin/true gogs/gogs 
docker run --name=gogs --volumes-from gogs-data gogs/gogs

[unknwon]

Thanks your explanation!

I'm kind of confused by dockerfile command VOLUME /data, what does it supposed to mean? Is it only for the purpose of giving the ability to mount to another data container?

[freemountain]

http://container-solutions.com/understanding-volumes-docker:

In order to understand what a Docker volume is, we first need to be clear about how the filesystem normally works in Docker. Docker images are stored as series of read-only layers. When we start a container, Docker takes the read-only image and adds a read-write layer on top. If the running container modifies an existing file, the file is copied out of the underlying read-only layer and into the top-most read-write layer where the changes are applied. The version in the read-write layer hides the underlying file, but does not destroy it — it still exists in the underlying image. When a Docker container is deleted, relaunching the image will start a fresh container without any of the changes made in the previously running container — those changes are lost. Docker calls this combination of read-only layers with a read-write layer on top a Union File System.

https://docs.docker.com/reference/builder/#volume:

The VOLUME instruction creates a mount point with the specified name and marks it as holding externally mounted volumes from native host or other containers.

Adding VOLUME /dataist the same as using docker run -v /data .... It tells docker to bybass the Union File System for /data.

I hope this helps, if not, feel free to ask me again

[unknwon]

Thank you, very helpful!

So there should I add this line VOLUME /data in the Dockerfile?

[freemountain]

That would be cool.
But i think you should also add this to the docs:

# Create data container
docker run --name=gogs-data --entrypoint /bin/true gogs/gogs
# Use `docker run` for the first time.
docker run --name=gogs --volumes-from gogs-data -p 10022:22 -p 10080:3000 gogs/gogs
# Use `docker start` if you have stopped it.
$ docker start gogs 

But this makes it harder to change the config files or the ssh keys...

[unknwon]

But this makes it harder to change the config files or the ssh keys...

If it's harder, why need add this though?

[freemountain]

Good point.
If you add VOLUME /datato the dockerfile you have two options handling persistent data:
Method one:

# Create data container
docker run --name=gogs-data --entrypoint /bin/true gogs/gogs
# Use `docker run` for the first time.
docker run --name=gogs --volumes-from gogs-data -p 10022:22 -p 10080:3000 gogs/gogs

Method two (the old one):

# Create local directory for volume.
$ mkdir -p /var/gogs
# Use `docker run` for the first time.
$ docker run --name=gogs -p 10022:22 -p 10080:3000 -v /var/gogs:/data gogs/gogs

You should add VOLUME into the Dockerfile, becaue both methods work now but I dont knwo which method should be mentioned in the docs.
Method one prevents permission issues, will work with remote docker hosts and is the recommended one (IMHO). The fact that the config files and keys are hidden is a Limitation.

[unknwon]

Thanks for explanation!

So if people who choose to use methods two, there is nothing different after I add line VOLUME, right?

I can put both docs in the README and explain to them they are free to choose one of them.