8.docker镜像的分层、复用

1.查看镜像一共多少层(有文件变化的算一层)

[root@docker03 ~]# docker history centos6.9_nginx:v2 
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
ddd1ed983cc3        24 hours ago        /bin/sh -c #(nop)  CMD ["nginx" "-g" "daemon…   0B                  
98ebae6b5ec0        24 hours ago        /bin/sh -c yum install -y nginx                 251MB               
37c018727de1        24 hours ago        /bin/sh -c curl -o /etc/yum.repos.d/CentOS-B…   2.52kB              
798035c21566        24 hours ago        /bin/sh -c curl -o /etc/yum.repos.d/epel.rep…   664B                
2199b8eb8390        9 months ago        /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B                  
<missing>           9 months ago        /bin/sh -c #(nop)  LABEL name=CentOS Base Im…   0B                  
<missing>           9 months ago        /bin/sh -c #(nop) ADD file:0e6d175401c5b4260…   195MB