The method of saving the docker system as a new image after modification

Environment: Fedora release 32 (Thirty Two)

Method 1: Use the export command to export, and then create a new image.
After modifying the system configuration, check the current container name or id, and execute the following command to generate a new image.

[root@Centos7 ~]# docker export 120f93e71bb1 >  myfedora.tar
[root@Centos7 ~]# cat myfedora.tar |docker import - mynewfedora:latest
sha256:349fbf8ea74700ce6fd0cc3f903ddcae7626cc5e3aeb9f89d415985fca6d8127
[root@Centos7 ~]# docker images
REPOSITORY            TAG                 IMAGE ID            CREATED             SIZE
mynewfedora           latest              349fbf8ea747        8 seconds ago       403MB

Method 2: Use the commit command to generate a new container image.

[root@Centos7 ~]# docker commit 120f93e71bb1 mynewfedora2
sha256:68ea6f3e4e0b8d0abedaba056d27944687d7cae842850111dffe3bddf908dba3
[root@Centos7 ~]# docker images
REPOSITORY            TAG                 IMAGE ID            CREATED             SIZE
mynewfedora2          latest              68ea6f3e4e0b        7 seconds ago       414MB
mynewfedora           latest              349fbf8ea747        3 minutes ago       403MB

TIPS : When running the container through the image created by the first method, there is an error as follows:

[root@Centos7 ~]# docker run -it mynewfedora
docker: Error response from daemon: No command specified.
See 'docker run --help'.

By comparing another image just now mynewfedora2 or the fedora image on the official website, it is found that in the image generated by this method, the parameter in Cmd is null, and the /bin/bash parameter of other images is missing:

[root@Centos7 ~]# docker inspect mynewfedora|grep -A 5 Cmd
            "Cmd": null,
            "Image": "",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
--
            "Cmd": null,
            "Image": "",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,

Compared:

[root@Centos7 ~]# docker inspect mynewfedora2|grep -A 5 Cmd
            "Cmd": [
                "/bin/bash"
            ],
            "ArgsEscaped": true,
            "Image": "fedora",
            "Volumes": null,
--
            "Cmd": [
                "/bin/bash"
            ],
            "ArgsEscaped": true,
            "Image": "fedora",
            "Volumes": null,

So when running the container with this image, you need to add /bin/bash to the command:

[root@Centos7 ~]# docker run -it mynewfedora /bin/bash
[root@515b2b933bb4 /]# 

Reference document:
https://blog.csdn.net/shenghuiping2001/article/details/93378185