While containers can create, update, and delete files, those changes are lost when the container is removed

Stopped container still keep the changes and can be restored by restarting the container

Store files in the host machine, so that the files are persisted even after the container is removed

Volumes are stored in a part of the host filesystem and managed by Docker

Non-Docker processes should not modify this part of the filesystem

A given volume can be mounted into multiple containers simultaneousl

Docker for Mac runs a virtual machine behind, and the volume's path is the path on the virtual machine

docker volume create [name] # create a volume
docker volume ls # list volumes
docker volume rm [volumeName] # remove one or more volumes
docker volume inspect [volumeName] # show volume information
        

docker volume create sandbox-home # create a named volume "sandbox-home"
docker run -v sandbox-home:/home -it busybox sh # run the sandbox linux

# create a readme file under /home and exit the sanbox
cd /home
touch readme
exit

# remove the container
docker rm [containerName]

docker run -v sandbox-home:/home -it busybox sh # run the sandbox linux again

# check the /home directory, readme file is still there
cd /home
ls
		

docker run -v sandbox-home:/home -it lchenlangley/hello sh # mount the volumn to a container running another image

# check the /home directory, readme file is there
cd /
ls
        

# two containers share one volumn
# changes in the mounted directory on one container will appear in the mounted directory on another container
docker run -v sandbox-home:/home -it lchenlangley/hello sh
docker run -v sandbox-home:/home -it busybox sh

# on the container with busybox
cd /home
touch hello2.py # create a file

# on the container of lchenlangley/hello
# check the /home directory, hello2.py file is there
cd /home
ls
        

Bind a host directory to a container directory

The files created on host or container do not appear in the container directory. Instead, they exist in the host directory

Both host and container can access the created files

# docker run -it -v [hostDirectory]:[containerDirectory] busybox sh, need absolute path
docker run -it -v $PWD/temp:/home busybox sh

# on container
cd /home
touch hello.py
ls # no file is there

# on host
cd $PWD/temp
ls # hello.py file is here
echo "print('Hello')" > hello.py

# on container
cat hello.py # can access hello.py, though hello.py does not appear in /home on container
        

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