docker 镜像基本操作

镜像是Docker的三大核心概念中最为重要的。Docker运行容器前需要本地存在对应的镜像，若没有镜像存在与本地，会先从仓库从获取下载。

获取镜像

docker官方提供数十万个镜像供大家下载，包括且不限于常用的ubuntu、apache、nginx、mysql、mongodb等常用的服务器及数据库等。

可使用docker pull命令从镜像源下载镜像。

docker pull：获取镜像

# 下载镜像 docker pull 镜像名[:tag]

root@ubuntu:~#  docker pull ubuntu
Using default tag: latest
latest: Pulling from library/ubuntu
3ff22d22a855: Pull complete 
e7cb79d19722: Pull complete 
323d0d660b6a: Pull complete 
b7f616834fd0: Pull complete 
Digest: sha256:5d1d5407f353843ecf8b16524bc5565aa332e9e6a1297c73a92d3e754b8a636d
Status: Downloaded newer image for ubuntu:latest
docker.io/library/ubuntu:latest

# 通过下载过程，可以看到，一个镜像一般是由多个层（layer） 组成，类似 f7e2b70d04ae这样的串表示层的唯一 ID。
# PS: 实际上完整的 ID 包括了 256 个 bit, 64 个十六进制字符组成的。

docker images 查看所有本地的主机上的镜像

docker images  #列出本地的镜像
# 解释
REPOSITORY	镜像的仓库源
TAG			镜像的标签
IMAGE ID    镜像的id
CREATED     创建的时间
SIZE        镜像的大小

# 可选项
	-a	--all    显示所有镜像，包括中间层
	-q  --quiet  仅显示镜像ID

docker search 搜索镜像

root@ubuntu:~# docker search mysql
NAME                              DESCRIPTION                                     STARS     OFFICIAL   AUTOMATED
mysql                             MySQL is a widely used, open-source relati...   9520      [OK]       
mariadb                           MariaDB is a community-developed fork of M...   3456      [OK]       

# 可选项
    --filter=STARS=3000 搜索starts>3000的镜像
root@a5-vm04:~# docker search mysql --filter=STARS=5000
NAME      DESCRIPTION                                     STARS     OFFICIAL   AUTOMATED
mysql     MySQL is a widely used, open-source relati...   9520      [OK]

docker rmi 删除镜像

docker rmi ID 删除指定的镜像
docker rmi -f $(docker images -aq)  删除全部的镜像

查看镜像

使用inspect命令查看镜像详细信息

通过docker inspect命令，可以获取镜像的详细信息，其中包括创建者、各层的数字摘要等。

root@ubuntu:~# docker inspect ubuntu
[
    {
        "Id": "sha256:1e4467b07108685c38297025797890f0492c4ec509212e2e4b4822d367fe6bc8",
        "RepoTags": [
            "ubuntu:latest"
        ],
        "RepoDigests": [
            "ubuntu@sha256:5d1d5407f353843ecf8b16524bc5565aa332e9e6a1297c73a92d3e754b8a636d"
        ],
        "Parent": "",
        "Comment": "",
        "Created": "2020-07-24T14:38:35.464294608Z",
        "Container": "9d62e8d762827123636cb28eacfed9975890fd659cac66adee63fc3a969bb8a9",
        "ContainerConfig": {
            "Hostname": "9d62e8d76282",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/sh",
                "-c",
                "#(nop) ",
                "CMD [\"/bin/bash\"]"
            ],
            "ArgsEscaped": true,
            "Image": "sha256:905a090e9b85447aff61cda51518fc1ab45af28e185981b70bc73dc9c03abf13",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": {}
        },
        "DockerVersion": "18.09.7",
        "Author": "",
        "Config": {
            "Hostname": "",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/bash"
            ],
            "ArgsEscaped": true,
            "Image": "sha256:905a090e9b85447aff61cda51518fc1ab45af28e185981b70bc73dc9c03abf13",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": null
        },
        "Architecture": "amd64",
        "Os": "linux",
        "Size": 73859057,
        "VirtualSize": 73859057,
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/0d948d7943f1db41d38707ae39e87bcf6dc842dbeb77c3b3ba332e366d38c02e/diff:/var/lib/docker/overlay2/b2160599c8339e155b44534f956ae2d1dab00cdf9e8cbbb1f013d5581f0771b8/diff:/var/lib/docker/overlay2/e64630287d462a45307b48add39bd3959d3c7e7c6b3404dd4c41e241d5d90b65/diff",
                "MergedDir": "/var/lib/docker/overlay2/d4e7ee51914e5a7b57f24cdff4882a9810c628d4fa3db1f806c2c5b259188085/merged",
                "UpperDir": "/var/lib/docker/overlay2/d4e7ee51914e5a7b57f24cdff4882a9810c628d4fa3db1f806c2c5b259188085/diff",
                "WorkDir": "/var/lib/docker/overlay2/d4e7ee51914e5a7b57f24cdff4882a9810c628d4fa3db1f806c2c5b259188085/work"
            },
            "Name": "overlay2"
        },
        "RootFS": {
            "Type": "layers",
            "Layers": [
                "sha256:ce30112909569cead47eac188789d0cf95924b166405aa4b71fb500d6e4ae08d",
                "sha256:8eeb4a14bcb4379021c215017c94800a848a8203a8ce76aa1bd211d4c995f792",
                "sha256:a37e74863e723df4ddd599ef1b7d9a68e2301794a8c37c2370f8c2c8993ef72c",
                "sha256:095624243293a7dfdb582f8471d6e2d9d7772dd621bc57906b034c59f388ebac"
            ]
        },
        "Metadata": {
            "LastTagTime": "0001-01-01T00:00:00Z"
        }
    }
]

使用history命令查看镜像历史

通过docker history命令，可以列出各个层(layer)的创建信息。

root@ubuntu:~# docker history ubuntu
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
1e4467b07108        3 weeks ago         /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B                  
<missing>           3 weeks ago         /bin/sh -c mkdir -p /run/systemd && echo 'do…   7B                  
<missing>           3 weeks ago         /bin/sh -c set -xe   && echo '#!/bin/sh' > /…   811B                
<missing>           3 weeks ago         /bin/sh -c [ -z "$(apt-get indextargets)" ]     1.01MB              
<missing>           3 weeks ago         /bin/sh -c #(nop) ADD file:65a1cc50a9867c153…   72.9MB