IO /question/24 in a very early post dockone. IO /question/24 someone asked: “Please tell me if the code is inside or outside the Docker”.

Because the code in the development environment is always changing, and many people collaborate with Git, the code is kept outside. Build an image of the runtime environment, and then use volume to map the code part into it, which is easy to adjust at any time.

My point of view is the same. At present, the Docker I have learned is mostly used for local development and has not yet been tested or deployed in a real environment. Therefore, I currently agree to use Docker as a deployment development environment, and then map the code and database into containers using volume.

So the topic of today’s article is: Learning Docker Volume

Docker Volume

A volume is a specially-designated directory within one or more containers that bypasses the Union File System. Volumes are designed to persist data, independent of the container’s life cycle. Docker therefore never automatically delete volumes when you remove a container, nor will it “garbage collect” volumes that are no longer referenced by a container. Also known as: data volume

There are three types of volumes: host, anonymous, and named:

• A host volume lives on the Docker host’s filesystem and can be email exchange from within the container.

• A named volume is a volume which Docker manages where on disk the volume is created, but it is given a name.

• An anonymous volume is similar to a named volume, however, it can be difficult, to refer to the same volume over time when it is an anonymous volumes. Docker handle where the files are stored.

Docker Volume is mounted

You can mount volumes using -v or create a data volume container using –volumes-from.

-v mounting mode

-v [host-dir]:[container-dir]:[rw|wo]Copy the code

Among them,

· Host-dir: indicates the directory on the host. If it does not exist, Docker will automatically create the directory on the host. · Container-dir: indicates the corresponding directory inside the container. If the directory does not exist, Docker will also create it inside the container. Rw | ro: used to control the volume of read and write permissions.

Therefore, [host-dir]:[container-dir] contains four combinations. Whether container-dir exists is not considered.

Host-dir = host-dir = host-dir

docker run -it -p 8890:8080 --rm -v /usr/local/tomcat/webapps --name test1 the tomcat: 8.0Copy the code

Then use the following command to view the data volume mounted in the container:

docker inspect test1Copy the code

The mount path seen at this point is temporary; The corresponding directory in the container is not overwritten either:

Host-dir = host-dir = host-dir = host-dir

docker run -it -d -p 8891:8080 --rm -v /Users/ye/docker/learning/javademo/volume2:/usr/local/tomcat/webapps --name testTomcat: 8.0Copy the code

Then use the following command to view the data volume mounted in the container:

docker inspect test2Copy the code

You can see that the host local folder is mounted on it:

At this point, we can see that the files in the corresponding directory in the container are the same as those in the host directory

If we add a file named world.java to the host, let’s see:

Stay consistent!

– volumes – from mount

Many times, we will deploy related containers on the same host and want them to share some data. At this point, we can create a data volume container that can then be mounted by multiple containers.

I will not continue to elaborate here, because I have learned that Docker Volume has not really used the data Volume container, so I have no say, after I have used the data Volume container, I will supplement the learning content in this area.

Data volume operation commands

There are mainly create, inspect, ls, prune and rm commands, among which ls is an example.

docker volume ls

List volumes Displays all data volumes

Command:

docker volume ls [OPTIONS]Copy the code

Such as:

[OPTIONS] command:

The other commands are relatively simple:

More reference website description: docs.docker.com/engine/refe…

conclusion

Although in the learning process, it is found that the mount method of using -V is more than that of using data volume container, mainly because of local learning or single project development. But in real product development, I believe –volume from will be used a lot, especially in production environments. Wait for us to continue to learn, also hope someone can lift me ~~~, thank you!

Coding01 looks forward to your attention

And thank you for seeing this