When Container is removed, data in it are also lost

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@server.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