1，docker镜像导入及导出

[root@centos7 ~]# docker images|grep centos
centos                                 latest              0d120b6ccaa8        4 days ago          215MB
[root@centos7 ~]# 
导出镜像：
[root@centos7 ~]# docker save centos > /root/centos.tar.gz
[root@centos7 ~]# ll
total 217160
-rw-------. 1 root root      1571 May 18  2019 anaconda-ks.cfg
-rw-r--r--. 1 root root 222366720 Aug 15 23:46 centos.tar.gz
[root@centos7 ~]# 
导入镜像：
[root@centos7 ~]# docker load < /root/centos.tar.gz 
Loaded image: centos:latest
[root@centos7 ~]# 


启动容器：
[root@centos7 ~]# docker run --name mydocker -ti centos /bin/bash
[root@ccf8a20bd407 /]# 
[root@ccf8a20bd407 /]# 
进入：
[root@centos7 ~]# docker attach mydocker

[root@centos7 ~]# yum install -y util-linux
[root@centos7 ~]# docker inspect -f '{{.State.Pid}}' mydocker
38547
[root@centos7 ~]# nsenter -t 38547 -m -u -i -n -p
[root@ccf8a20bd407 /]# 

[root@centos7 ~]# docker exec -it mydocker /bin/bash
[root@ccf8a20bd407 /]# 

将容器保存为镜像：
[root@centos7 ~]# docker ps -a|grep mydocker
ccf8a20bd407        centos                                 "/bin/bash"              16 minutes ago      Up 10 minutes                                        mydocker
[root@centos7 ~]# 
[root@centos7 ~]# 
[root@centos7 ~]# docker commit -m 'this-is-a-images' ccf8a20bd407 oldboy/my-centos:v1
sha256:1432890ec09ab6fce4c27fa3a91c8281e7718cfd852c3d142ee5357b09b127e0
[root@centos7 ~]# 
[root@centos7 ~]# docker images|grep centos
oldboy/my-centos                       v1                  1432890ec09a        15 seconds ago      215MB
centos                                 latest              0d120b6ccaa8        4 days ago          215MB
[root@centos7 ~]#