CentOS 8.x create and use containers with podman

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<yambe:breadcrumb self="Create and use containers with podman">CentOS 8.x podman|podman</yambe:breadcrumb>

CentOS 8.x create and use containers with podman

Check running containers

  • Get information on running containers using:
     podman ps
  • To get information on all containers including stopped containers use:
     podman ps --all


Start new containers

  • Start container with interactive shell:
     podman run -it centos bash
     #Then exit from container shell

where:

-i (--interactive)
is for keeping STDIN open even if not attached
-t (--tty)
is for allocating a pseudo-TTY for container


  • To give name to containers use:
     podman run -it --name web1 centos bash

Then name can be used in future podman commands such as rm or attach


Delete containers

  • To delete container using container ID use:
     podman ps --all  #List containers
     podman rm <container-id>

Note that only stopped containers can be deleted. To stop running container before deleting use: 

     podman stop <container-id>


Tag images

We can tag images to identify them easily using: 

     podman tag <image-id> <tag>


Search for images

Searching images in podman 

     podman search httpd


Get more image details

To see more details of image use: 

     podman inspect <image-id or image-tag>

This lists information such as:

  • Various tags of the image
  • Image sha256 checksum
  • WorkDir where we can find all files related to the image


See container logs

  • To see logs of container use:
     podman logs <container-id>

Note that this works even if there is no /var/log/messages file inside the container

  • To follow logs in realtime use:
     podman logs -f <container-id>
  • To see last few lines of container logs use:
     podman logs --tail 10 <container-id>


See list of process of running containers

To see running process inside container use: 

     podman top <container-id>


Get shell (attach) for running containers

To get shell (attach) for running containers use: 

   podman attach <container-id>

To come out of shell (detach) without existing use 'Ctrl+p+q'

Refer:


Accessing container files in base host

In base host do 

   df -h

and you can see container folder mounted as part of output such as: 

   overlay         222G   99G  113G  47% /mnt/data1/container-files/var-lib-containers/storage/overlay/405546df7603ca9e16d8a69a26cd7e44129b4f24312a8b1bc25841620b089ac5/merged

Then you can create new files in corresponding ../diff folder such as: 

   touch  /mnt/data1/container-files/var-lib-containers/storage/overlay/405546df7603ca9e16d8a69a26cd7e44129b4f24312a8b1bc25841620b089ac5/diff/a.txt

All the files of diff along with base files of image get merged and are shown in: 

   ls  /mnt/data1/container-files/var-lib-containers/storage/overlay/405546df7603ca9e16d8a69a26cd7e44129b4f24312a8b1bc25841620b089ac5/merged/*.txt

You can do "ls /*.txt" in container to see a.txt file.


Install packages in podman containers from base host

To install packages in podman containers having same OS (eg centos8) use: 

   yum -y install --installroot=/mnt/data1/container-files/var-lib-containers/storage/overlay/8e81551668e86c7cac3e425f0f9d6207736c9a43d53fe5f9abdc9d3b07fc8e56/merged bind-utils

where the installroot path can be found using: 

   podman inspect <container-id-or-name> | grep -i merged



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