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Lab 004: Save, Load and Transfer Docker Image

Requirements​

One of the DevOps team members was working on to create a new custom docker image on App Server 1 in Stratos DC. He is done with his changes and image is saved on same server with name games:devops. Recently a requirement has been raised by a team to use that image for testing, but the team wants to test the same on App Server 3. So we need to provide them that image on App Server 3 in Stratos DC.

a. On App Server 1 save the image games:devops in an archive. b. Transfer the image archive to App Server 3. c. Load that image archive on App Server 3 with same name and tag which was used on App Server 1.

Note: Docker is already installed on both servers; however, if its service is down please make sure to start it.

Note

This page preserves the original task text and documents one image-transfer workflow: save, copy, load, and verify the resulting image tag on the destination host.

Prerequisites​

  • You can SSH to App Server 1 and App Server 3 and switch to a privileged shell on both hosts.
  • Docker is installed on both servers and the source image games:devops already exists on App Server 1.
  • The destination path /tmp is writable for transferring the archive file.

Steps​

Login to the app server 1 and switch to root. For the server credentials, check out the Project Nautilus documentation.

sshpass -p  '*********' ssh -o StrictHostKeyChecking=no tony@172.16.238.10
sudo su -
*********

Check the docker images.

[root@stapp01 ~]# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED              SIZE
games               devops              e60b0cf7872c        About a minute ago   121MB
ubuntu              latest              01f29b872827        2 weeks ago          77.8MB

Save the image in an archive file and then verify.

docker save -o /tmp/games.tar games:devops 
[root@stapp01 ~]# ls -la /tmp/ | grep tar
-rw------- 1 root root 123116544 Aug 18 13:28 games.tar

Use SCP to copy the file to app server 3. Note that you may get permission issues if you copy the tar file to some directories in the app server 3. To prevent this, use the /tmp directory as the destination.

scp /tmp/games.tar banner@stapp03:/tmp

Open a second tab, login to the app server 3, and switch to root. For the server credentials, check out the Project Nautilus documentation.

sshpass -p  '**********' ssh -o StrictHostKeyChecking=no banner@172.16.238.12
sudo su -
**********

Confirm that the file is copied onto the /tmp directory.

[root@stapp03 ~]# ls -la /tmp | grep tar
-rw------- 1 banner banner 123116544 Aug 18 13:29 games.tar

Load the image from the archive file.

docker load -i /tmp/games.tar

Verify by checking the images. Make sure it has the same image name and tag.

[root@stapp03 ~]# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
games               devops              e60b0cf7872c        5 minutes ago       121MB

Verification​

  • Confirm the archive exists on App Server 1 with ls -la /tmp | grep games.tar before transfer.
  • Confirm the archive arrives on App Server 3 with ls -la /tmp | grep games.tar.
  • Confirm the image tag games:devops is present on App Server 3 with docker images | grep 'games\s\+devops'.

Resources​