CentOS Stream 8
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Podman : Use External Storage
2021/03/22
 
When a Container is removed, data in it are also lost, so it's necessary to use external storage on Containers if you'd like to save your data on Containers.
[1] It's possible to mount a directory on Docker Host into Containers.
# create a directory for containers data

[root@dlp ~]#
mkdir /var/lib/containers/disk01

[root@dlp ~]#
echo "persistent storage" >> /var/lib/containers/disk01/testfile.txt

# run a Container with mounting the directory above on [/mnt]

# if SELinux is [Enforcing], it needs to add [--privileged] option

[root@dlp ~]#
podman run --privileged -it -v /var/lib/containers/disk01:/mnt centos /bin/bash
[root@43b1ee70639f /]#
df -hT /mnt

Filesystem          Type  Size  Used Avail Use% Mounted on
/dev/mapper/cs-root xfs    71G  3.2G   68G   5% /mnt

[root@43b1ee70639f /]#
cat /mnt/testfile.txt

persistent storage
[2] It's also possible to configure external storage by Docker Data Volume command.
# create [volume01] volume

[root@dlp ~]#
podman volume create volume01

volume01
# display volume list

[root@dlp ~]#
podman volume ls

DRIVER      VOLUME NAME
local       volume01

# display details of [volume01]

[root@dlp ~]#
podman volume inspect volume01

[
    {
        "Name": "volume01",
        "Driver": "local",
        "Mountpoint": "/var/lib/containers/storage/volumes/volume01/_data",
        "CreatedAt": "2021-03-17T20:46:26.011207388-06:00",
        "Labels": {},
        "Scope": "local",
        "Options": {}
    }
]

# run a container with mounting [volume01] to [/mnt] on container

[root@dlp ~]#
podman run -it -v volume01:/mnt centos
[root@dc43ed479137 /]#
df -hT /mnt

Filesystem          Type  Size  Used Avail Use% Mounted on
/dev/mapper/cs-root xfs    71G  3.2G   68G   5% /mnt

[root@dc43ed479137 /]#
echo "Podman Volume test" > /mnt/testfile.txt

[root@dc43ed479137 /]#
exit
[root@dlp ~]#
cat /var/lib/containers/storage/volumes/volume01/_data/testfile.txt

Podman Volume test
# possible to mount from other containers

[root@dlp ~]#
podman run -v volume01:/var/volume01 centos /usr/bin/cat /var/volume01/testfile.txt

Podman Volume test
# to remove volumes, do like follows

[root@dlp ~]#
podman volume rm volume01

Error: volume volume01 is being used by the following container(s): 736c57cc37d8eb8b2f2b43065243758cfd08f32acae3966826c4131daaeaf439, dc43ed479137dc10deaf3e33f5478ec431d87b4afbd9f69bc7a9b94ccffb17b7: volume is being used

# if some containers are using the volume you'd like to remove like above,

# it needs to remove target containers before removing a volume

[root@dlp ~]#
podman rm 736c57cc37d8eb8b2f2b43065243758cfd08f32acae3966826c4131daaeaf439

[root@dlp ~]#
podman rm dc43ed479137dc10deaf3e33f5478ec431d87b4afbd9f69bc7a9b94ccffb17b7
[root@dlp ~]#
podman volume rm volume01

volume01
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