Share files between two containers

You can use volumes to persist data in containers even after the container is deleted. A volume is a folder stored on the host machine that does not increase the container size and can be shared among multiple containers, making it easier to back up or migrate data.

Before you begin

  • The container-tools meta-package is installed.

Procedure

  1. Create a volume: 
    $ podman volume create hostvolume
  2. Display information about the volume: 
    $ podman volume inspect hostvolume
     
    [
    {
        "name": "hostvolume",
        "labels": {},
        "mountpoint": "/home/username/.local/share/containers/storage/volumes/hostvolume/_data",
        "driver": "local",
        "options": {},
        "scope": "local"
    }
]

    Notice that it creates a volume in the volumes directory. You can save the mount point path to the variable for easier manipulation: $ mntPoint=$(podman volume inspect hostvolume --format {{.Mountpoint}}).

    Notice that if you run sudo podman volume create hostvolume, then the mount point changes to /var/lib/containers/storage/volumes/hostvolume/_data.

  3. Create a text file inside the directory using the path that is stored in the mntPoint variable: 
    $ echo "Hello from host" >> $mntPoint/host.txt
  4. List all files in the directory defined by the mntPoint variable: 
    $ ls $mntPoint/
     
    host.txt
  5. Run the container named myubi1 and map the directory defined by the hostvolume volume name on the host to the /containervolume1 directory on the container: 
    $ podman run -it --name myubi1 -v hostvolume:/containervolume1 registry.access.redhat.com/ubi10/ubi /bin/bash

    Note that if you use the volume path defined by the mntPoint variable (-v $mntPoint:/containervolume1), data can be lost when running podman volume prune command, which removes unused volumes. Always use -v hostvolume_name:/containervolume_name.

  6. List the files in the shared volume on the container: 
    # ls /containervolume1
     
    host.txt

    You can see the host.txt file which you created on the host.

  7. Create a text file inside the /containervolume1 directory: 
    # echo "Hello from container 1" >> /containervolume1/container1.txt
  8. Detach from the container with CTRL+p and CTRL+q.
  9. List the files in the shared volume on the host, you can see two files: 
    $ ls $mntPoint
     
    container1.rxt  host.txt

    At this point, you are sharing files between the container and host. To share files between two containers, run another container named myubi2.

  10. Run the container named myubi2 and map the directory defined by the hostvolume volume name on the host to the /containervolume2 directory on the container: 
    $ podman run -it --name myubi2 -v hostvolume:/containervolume2 registry.access.redhat.com/ubi10/ubi  /bin/bash
  11. List the files in the shared volume on the container: 
    # ls /containervolume2
     
    container1.txt host.txt

    You can see the host.txt file which you created on the host and container1.txt which you created inside the myubi1 container.

  12. Create a text file inside the /containervolume2 directory: 
    # echo "Hello from container 2" >> /containervolume2/container2.txt
  13. Detach from the container with CTRL+p and CTRL+q.
  14. List the files in the shared volume on the host, you should see three files: 
    $ ls $mntPoint
     
    container1.rxt  container2.txt host.txt

    For more information, see the podman-volume(1) man page on your system.