Implementation of local migration of docker images

I've been learning Docker recently, and I often encounter a problem: when downloading Docker images, they fail due to well-known network reasons. Although there are many solutions online, such as using domestic mirror services such as Docker Hub Mirror, due to personal reasons (luckily I have a foreign VM), I prefer not to share the downloaded images through the Docker registry.

The problem is clear:

Share the docker image on machine A to other machines without going through the docker registry, that is, local migration of the docker image.

The solution is also very simple:

Use Docker's save and load commands. The specific steps are as follows

1. List all docker images on machine A and find the image name you want to save

sudo docker images

2. Use the docker save command on machine A to save the image as a tar file

sudo docker save image_name -o file_path

Here, image_name is replaced with the name of the image to be saved found in the first step. file_path is the exported tar file path, such as /home/tmp/image1.tar

3. Transfer the exported image tar file to another machine, such as machine B. You can use various methods, such as scp, etc., which will not be described in detail here.

4. Use the docker load command to load the image tar file on the machine that needs to use the image (such as machine B)

sudo docker load -i file_path

Note: In addition, you can also use Docker's export and import commands to achieve similar functions. You can check the differences between export/save and import/load on the Internet, so I won't expand on them here.

The basic difference is that what is exported is a container (without history and layer information), while what is saved is an image (with complete history and layer information, supporting layer rollback)

Supplement: Backup and migration of Docker images

first step:

Use the docker ps -a command to view all containers

[root@localhost ~]# docker ps -a 
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
9505a10e6d29 nginx "nginx -g 'daemon of..." 34 minutes ago Exited (0) 8 minutes ago mynginx
4c89fff9ac8c mysql:5.6 "docker-entrypoint.s..." 11 days ago Exited (0) 11 days ago mymysql
0abefefe2592 centos "/bin/bash" 2 months ago Exited (255) 12 days ago mycentos

Step 2:

The container is saved as an object, docker commit container name to be saved

[root@localhost conf]# docker commit mynginx mynginx_backup
sha256:a6ca067596a2c319ddcdc9592afa9a7e9be4c157959c0327214d3e577333ed3a

Step 3:

View the image just saved

[root@localhost conf]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
mynginx_backup latest a6ca067596a2 19 seconds ago 109MB

Step 4:

Image backup (saved as tar file), docker save -o container name.tar name to be saved

[root@localhost ~]# docker save -o mynginx.tar mynginx_backup

Step 5:

View the current directory

[root@localhost ~]# ls
anaconda-ks.cfg conf data initial-setup-ks.cfg java logs mynginx.tar original-ks.cfg

Step 6:

Delete the original image and view

[root@localhost ~]# docker rmi mynginx_backup
Untagged: mynginx_backup:latest
Deleted: sha256:a6ca067596a2c319ddcdc9592afa9a7e9be4c157959c0327214d3e577333ed3a
Deleted: sha256:facd3b28655186bdc7349bc017557ed80f94155831a8a3ed936f498e2f5b6b1c
[root@localhost ~]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE

Step 7:

Image recovery, docker load -i packaged container file name.tar

[root@localhost ~]# docker load -i mynginx.tar 
ea4399e4dbe6: Loading layer [===================================================>] 6.656kB/6.656kB
Loaded image: mynginx_backup:latest
[root@localhost ~]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
mynginx_backup latest a6ca067596a2 7 minutes ago 109MB

Step 8:

Use this image to create a container

[root@localhost ~]# docker run --name mynginx2 -p 80:80 -d mynginx_backup
a4809747f3c233d5a8f0c35542449adda10c06305f32c32a55e4842630212760

Step 9:

Enter the IP address in the browser to see if it is successful

The above is my personal experience. I hope it can give you a reference. I also hope that you will support 123WORDPRESS.COM. If there are any mistakes or incomplete considerations, please feel free to correct me.