Docker Storage
To keep data for the container is called container's storage.
Docker storage is only available on Linux.
Types of Storage
|
Non Persistent In this type of storage, the
data will be lost if the container is deleted. tmpfs
In this file system, the data will be stored in
memory and it is only available during the container's
lifetime, which means if the container is stopped or
deleted the data will be lost. It is more suitable for the in-memory
calculation. |
Persistent In
this type of storage, the data will be persisted even though the container
gets deleted. Docker Volume It is the
storage that is maintained by the docker daemon in the docker area.. The
default storage location is /var/lib/docker/volumes folder. Bind Mount It is the storage
that is managed by the admin of the system. It is a file or directory which
is maintained on the host machine. |
Docker Volume
It is the storage that is maintained by the docker daemon in the docker area.. The default storage location is /var/lib/docker/volumes folder
Docker volume Commands:
|
create |
Create a volume |
|
inspect |
Display detailed
information on one or more volumes |
|
ls |
List volumes |
|
prune |
Remove all unused local
volumes |
|
rm |
Remove one or more volumes |
Bind Mount
It is the storage that is managed by the admin of the system. It is a file or directory which is maintained on the host machine. It is having fewer features as compared to docker volume and it does not have any formal commands to manage these volumes by docker. You can use -v or --mount option to mount a directory of your host machine to the container
Example of Non-Persistent Storage:
Example 1:-
Step 1: Create a container using ubuntu docker image
docker container run -it --name tmpcontainer -d ubuntu
Step 2: Go inside the container
docker exec -it tmpcontainer bash
Step 3: In this container, create a directory call test and store some files into it.
- mkdir test
- cd test
- touch file1 file2 file3 file4
- ls
Step 4: Stop the container.
docker stop tmpcontainer
Step 5: Start the container and check the test director still persist with all its files.
- docker start tmpcontainer
- docker exec -it tmpcontainer bash
- ls test
Step 6: Delete the container and think is there any way to get your test directory again.
docker rm -f tmpcontainer
No there is no way to get back the test directory data, because the container is deleted so storage in this container was non-persistent.
Example 2:- (tmpfs)
Step 1: Create a container using ubuntu docker image.
docker container run -it --name tmpcontainer --mount type=tmps,destination=/test -d ubuntu
Step 2: Go inside the container
docker exec -it tmpcontainer bash
Step 3: In this container, create a directory call test and store some files into it.
- cd test
- touch file1 file2 file3 file4
- ls
Step 4: Stop the container.
docker stop tmpcontainer
Step 5: Start the container and check the test director still persist with all its files or not. The files should be removed means you will not get any data inside test folder..
docker start tmpcontainerdocker exec -it tmpcontainer bash
ls test
Step 6: Delete the container and think is there any way to get your test directory again.
docker rm -f tmpcontainer
No there is no way to get back the test directory data, because the container is deleted so storage in this container was non-persistent.
Example 3:- (tmps with tmpfs-mode)
Create a container with tmpfs and change the permission of destination folder.
docker container run -it --name c1 --mount type=tmpfs,destination=/tmp1,tmpfs-mode=1700 -d ubuntu
Example of Persistence Storage
Example 1:- (docker volume)
To delete all unused docker volumes:
docker volume prune
Step 1: To create a docker volume (demo-vol)
docker volume create demo-vol
Step 2: List all docker volumes
docker volume ls
Step 3: By default the driver is local and path for this docker volume is /var/lib/docker/volume.
ls /var/lib/docker/volumes/demo-vol/_data
Step 4: Run a container which points its /app directory to demo-vol
docker container run -it --name c1 --mount source=demo-vol,destination=/app -d ubuntu
Step 5: Go inside the container
docker exec -it c1 bash
Step 6: Create some files under /app directory
cd app
touch file1 file2 file3 file4
exit
Step 7: Check these files are available under demo-volume's directory
ls /var/lib/docker/volumes/demo-vol/_data
Step 8: Delete file4 from _data directory and check in c1 container's /app directory, file4 should not be available under this directory.
rm /var/lib/docker/volumes/demo-vol/_data/file4
docker exec -it c1 bash
ls /app
Step 9: Add a new file file5 in-app directory of the container and check this file should be available in demo-volume's data directory.
cd app
touch file5
exit
ls /var/lib/docker/volumes/demo-vol/_data
Step 10: Delete container c1.
docker rm -f c1
Step 11: Make sure your demo-vol data is not deleted.
ls /var/lib/docker/volumes/demo-vol/_data
Step 12: Create a new container and attach demo-vol to that container's /demo directory.
docker container run -it --name c2 --mount source=demo-vol,destination=/demo -d centos
docker exec -it c2 bash
ls demo
Step 14: Delete the volume. Deletion of volume will delete the data as well.
docker rm -f c2
docker volume rm demo-vol
Note: You can use -v option instead of --mount with docker volume to mount a volume eg.
docker container run -it --name c3 -v demo-vol:/demo -d centos
Note: You can also refer to an existing directory of containers that points to docker volume.
docker container run -it --name c3 -v demo-vol:/root -d centos
In the above example, root directory's all files will be stored under demo-vol's data directory.
Example 2:- (Bind Mount)
Step 1: Create a directory (/home/vagrant/myfiles) that you want to map with the container's target directory
mkdir /home/vagrant/myfiles
Step 2: Run a container which maps myfiles directory to container's /app1 directory.
docker container run -it --name bindmountcontainer -v /home/vagrant/myfiles:/app1 -d ubuntu
OR
docker container run -it --name bindmountcontainer --mount type=bind,source=/home/vagrant/myfiles,target=/app1 -d ubuntu
Step 3: Go inside the container and add some files in app1 directory
docker exec -it bindmountcontainer bash
cd app1
touch file1 file2 file3 file4
exit
Step 4: Go to myfiles directory and find all the files that exist in this folder or not.
ls myfiles
