docker基础_docker镜像与分层

docker镜像与分层

docker镜像由一些松耦合的制度镜像层组成

docker负责堆叠这些镜像层并将它们表示为单个统一的对象

当 docker image pull ubuntu:latest 时 每一行 pull complete就代表拉取完成了一层

查看镜像分层的方式 docker image inspect

beginner@beginner-virtual-machine:~$ docker pull tomcat
Using default tag: latest
latest: Pulling from library/tomcat
0e29546d541c: Pull complete 
9b829c73b52b: Pull complete 
cb5b7ae36172: Pull complete 
6494e4811622: Pull complete 
668f6fcc5fa5: Pull complete 
dc120c3e0290: Pull complete 
8f7c0eebb7b1: Pull complete 
77b694f83996: Pull complete 
0f611256ec3a: Pull complete 
4f25def12f23: Pull complete 
Digest: sha256:9dee185c3b161cdfede1f5e35e8b56ebc9de88ed3a79526939701f3537a52324
Status: Downloaded newer image for tomcat:latest
docker.io/library/tomcat:latest
可以发现拉取的时候tomcat一共有十层

docker 将所有镜像层堆叠合并，对外提供统一的视图

共享镜像层

docker pull tomcat

• 假设一共有十层 ,当发现本地存在dc120c3e0290这个镜像层时 就不会再次拉取 而是直接使用本地的镜像层

• 当不再需要某个镜像的时候，可以通过 docker image rm 命令从 Docker 主机删除该镜像。其中，rm 是 remove 的缩写。删除操作会在当前主机上删除该镜像以及相关的镜像层。这意味着无法通过 docker image ls 命令看到删除后的镜像，并且对应的包含镜像层数据的目录会被删除。但是，如果某个镜像层被多个镜像共享，那只有当全部依赖该镜像层的镜像都被删除后，该镜像层才会被删除。

容器生成镜像

当通过commit命令 使用当前容器生成镜像时，新的镜像就会多出一层 是可写容器生成的层数

beginner@beginner-virtual-machine:~$ docker run -d -p 8080:8080 tomcat:latest
5cc1beeff39b8b249b4329ff9319737062693f7b3817eedd8b9d757498cc42b1
beginner@beginner-virtual-machine:~$ docker container ls
CONTAINER ID   IMAGE           COMMAND             CREATED          STATUS          PORTS                                       NAMES
5cc1beeff39b   tomcat:latest   "catalina.sh run"   11 seconds ago   Up 10 seconds   0.0.0.0:8080->8080/tcp, :::8080->8080/tcp   clever_goldberg

beginner@beginner-virtual-machine:~$ docker exec -it clever_goldberg bash
root@5cc1beeff39b:/usr/local/tomcat# mkdir helloworld
root@5cc1beeff39b:/usr/local/tomcat# exit
exit
beginner@beginner-virtual-machine:~$ docker commit clever_goldberg test:1.0
sha256:5535c3a6ec2412eb1eeaa7a01ac2c40645f7c105a340c6a3de03e9a25195d830
beginner@beginner-virtual-machine:~$ docker inspect test:1.0
=====================================
"Layers": [
                "sha256:11936051f93baf5a4fb090a8fa0999309b8173556f7826598e235e8a82127bce",
                "sha256:31892cc314cb1993ba1b8eb5f3002c4e9f099a9237af0d03d1893c6fcc559aab",
                "sha256:8bf42db0de72f74f4ef0c1d1743f5d54efc3491ee38f4af6d914a6032148b78e",
                "sha256:26a504e63be4c63395f216d70b1b8af52263a5289908df8e96a0e7c840813adc",
                "sha256:f9e18e59a5651609a1503ac17dcfc05856b5bea21e41595828471f02ad56a225",
                "sha256:832e177bb5008934e2f5ed723247c04e1dd220d59a90ce32000b7c22bd9d9b54",
                "sha256:3bb5258f46d2a511ddca2a4ec8f9091d676a116830a7f336815f02c4b34dbb23",
                "sha256:59c516e5b6fafa2e6b63d76492702371ca008ade6e37d931089fe368385041a0",
                "sha256:bd2befca2f7ef51f03b757caab549cc040a36143f3b7e3dab94fb308322f2953",
                "sha256:3e2ed6847c7a081bd90ab8805efcb39a2933a807627eb7a4016728f881430f5f",
                "sha256:80b815ac2177a578ce5b28818a5835413957cdb8c146ffcedfa26f520aad3074"
            ]

=====================================
现在是十一层