[Docker] volume with CLI

 

 

 

 

🎯 What's target?

Sometimes we neeeds share and backup & restore among multiple containers.

It's time to use volume.

 

Volume path according to Host OS

Host OS	path
Linux	/var/lib/docker (standard)
Windows	?? (VM)
Mac	~/Libfrary/Containers/com.docker.docker/Data/vms/0/tty (VM)

 

Windows, Mac both use Virtual machine based on linux since docker use default linux mechanism

 

 

Step by Step using data container backup and restore

 

1. Create your volume

# create volume with explicit name
# In this example, use the name of 'shared-volume'
$ docker volume create shared-volume

2. Data container with volume mapping

# make data container mapping the volume you created.
# In this example, use '/data-volume'
$ docker run -it --name data-container \
-v shared-volume:/data-volume \
ubuntu:22.04

Check it what it be made successfully

# 'data-volume' directory is created in container
$ ls
bin   data-volume  etc  lib lib64 media  opt   root  sbin  sys  usr
boot  dev    home  lib32 libx32 mnt    proc  run   srv  tmp  var

 

3. make other container using '--volumes-from' option

--volumes-from

Use this for mount volumes from data container which you have already made.

 

# --voluems-from [container-name] (you want to mount)
$ docker run -it --name container1 \
> --volumes-from data-container \
> ubuntu:20.04

Check it what it be made successfully and share the same volume between data-container and container1

root@2e26227154cc:/# ls
bin   data-volume  etc   lib    lib64   media  opt   root  sbin  sys  usr
boot  dev          home  lib32  libx32  mnt    proc  run   srv   tmp  va

 

Share the volume only 'data-volume' between multiple containers 

 

4. create file in shared volume

# container1
root@2e26227154cc:/data-volume# echo 'test1' > test1.txt
root@2e26227154cc:/data-volume# ls
test1.txt

# container2
root@a3d7e231e702:/data-volume# ls
test1.txt

 

volume is alive! even though data container is removed.

# remove containers except the container2
$ docker container rm data-container container1

The file 'test1.txt' is remain after removed other containers

# container2
root@a3d7e231e702:/data-volume# ls
test1.txt

 

Remove volumes

A Docker data volume persists after a container is deleted. There are two types of volumes to consider:
- Named volumes have a specific source from outside the container, for example awesome:/bar.
- Anonymous volumes have no specific source so when the container is deleted, instruct the Docker Engine daemon to remove them.
                                                                               - [Docker volume documents]

 

Summary in picture

 

 

 

Volume vs Bind mount

	Volume	Bind Mount
Why to use	Share persistent data
When to use	Share data among containers ex) DB data	- Share data between host os and container - Edit on host and reflect in container ex) Source code
Rebuild required?	True	False

 

Use anonymous volume only when you need prioritizing docker internal path than external path. (Host OS)

For example, set anonymous volume on `node_modules` per each app container which have separately

 

 

 

📝 Conclusion

Usually use named volume with -v option
{volume-name}:{container-volume-path}

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🔗 Reference

Demystifying Docker Volumes for Mac and PC Users

 

Use volumes