Docker : Use Persistent Storage

When Container is removed, data in it are also lost, so it's necessary to use external filesystem in Container as persistent storage if you need.
[1]	For exmaple, create a Container only for using to save data as a storage server with an image busybox.

[root@dlp ~]#  vi Dockerfile # create new FROM busybox MAINTAINER ServerWorld <admin@srv.world> VOLUME /storage CMD /bin/sh # build image [root@dlp ~]#  docker build -t storage . [root@dlp ~]#  docker images  REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE storage latest 65c5cce81114 20 seconds ago 1.113 MB docker.io/centos latest 14dab3d40372 6 days ago 194.7 MB docker.io/busybox latest fc0db02f3072 13 days ago 1.113 MB # generate a Container with any name you like [root@dlp ~]#  docker run -i -t --name storage_server storage  / #  exit

[2]	To use the Container above as a Storage Server from other Containers, add an option "--volumes-from".

[root@dlp ~]#  docker run -i -t --name centos_server --volumes-from storage_server centos /bin/bash [root@b9b7a2d35b51 /]#  df -hT  Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/docker-253:0-67164897-..... ext4 99G 266M 94G 1% / tmpfs tmpfs 2.0G 0 2.0G 0% /dev shm tmpfs 64M 0 64M 0% /dev/shm tmpfs tmpfs 2.0G 0 2.0G 0% /sys/fs/cgroup /dev/mapper/centos-root xfs 27G 3.2G 24G 13% /storage tmpfs tmpfs 2.0G 0 2.0G 0% /run/secrets [root@b9b7a2d35b51 /]#  echo "persistent storage" >> /storage/testfile.txt  [root@b9b7a2d35b51 /]#  ll /storage  total 4 -rw-r--r-- 1 root root 19 Dec 22 02:15 testfile.txt

[3]	Make sure data are saved to run a Container of Storage Server like follows.

[root@dlp ~]#  docker start storage_server  [root@dlp ~]#  docker attach storage_server  / #  cat /storage/testfile.txt  persistent storage

[4]	For other way to save data in external filesystem, it's possible to mount a directory on Docker Host into Containers.

# create a directory [root@www ~]#  mkdir -p /var/docker/disk01  [root@www ~]#  echo "persistent storage" >> /var/docker/disk01/testfile.txt # run a Container with mounting the directory above on /mnt [root@www ~]#  docker run -i -t -v /var/docker/disk01:/mnt centos /bin/bash [root@bc9a4d5578a6 /]#  df -hT  Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/docker-253:0-67164897-..... ext4 99G 266M 94G 1% / tmpfs tmpfs 2.0G 0 2.0G 0% /dev shm tmpfs 64M 0 64M 0% /dev/shm tmpfs tmpfs 2.0G 0 2.0G 0% /sys/fs/cgroup /dev/mapper/centos-root xfs 27G 3.2G 24G 13% /mnt tmpfs tmpfs 2.0G 0 2.0G 0% /run/secrets [root@bc9a4d5578a6 /]#  cat /mnt/testfile.txt  persistent storage