继续学习入门知识。前面已经安装了dokcer，现在来看看 docker image的相关命令
[ec2-user@ip-172-16-1-4 ~]$ sudo docker image
Usage: docker image COMMAND
Manage images
Commands:
build Build an image from a Dockerfile
history Show the history of an image
import Import the contents from a tarball to create a filesystem image
inspect Display detailed information on one or more images
load Load an image from a tar archive or STDIN
ls List images
prune Remove unused images
pull Pull an image or a repository from a registry
push Push an image or a repository to a registry
rm Remove one or more images
save Save one or more images to a tar archive (streamed to STDOUT by default)
tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE下面按顺序简单的过一遍
build是创建镜像，这个后面会有具体介绍
history 可以看见镜像的历史。docker的镜像是一个多层的结构，比如说，这个里面的结构其实都是我们在创建docker镜像到时候输入的命令
127MB
[ec2-user@ip-172-16-1-4 ~]$ sudo docker image history nginx
IMAGE CREATED CREATED BY SIZE COMMENT
8cf1bfb43ff5 2 days ago /bin/sh -c #(nop) CMD ["nginx" "-g" "da emon… 0B
2 days ago /bin/sh -c #(nop) STOPSIGNAL SIGTERM 0B
2 days ago /bin/sh -c #(nop) EXPOSE 80 0B
2 days ago /bin/sh -c #(nop) ENTRYPOINT ["/docker- entr… 0B
2 days ago /bin/sh -c #(nop) COPY file:0fd5fca330dc d6a7… 1.04kB
2 days ago /bin/sh -c #(nop) COPY file:1d0a4127e78a 26c1… 1.96kB
2 days ago /bin/sh -c #(nop) COPY file:e7e183879c35 719c… 1.2kB
2 days ago /bin/sh -c set -x && addgroup --syst em -… 63.3MB
2 days ago /bin/sh -c #(nop) ENV PKG_RELEASE=1~bus ter 0B
2 days ago /bin/sh -c #(nop) ENV NJS_VERSION=0.4.2 0B
2 days ago /bin/sh -c #(nop) ENV NGINX_VERSION=1.1 9.1 0B
2 days ago /bin/sh -c #(nop) LABEL maintainer=NGIN X Do… 0B
2 days ago /bin/sh -c #(nop) CMD ["bash"] 0B
2 days ago /bin/sh -c #(nop) ADD file:6ccb3bbcc69b0 d44c… 69.2MB import 是从一个tar文件里面导入容器的文件系统来生成一个镜像，对应的我们可以从docker container的命令里面export一个容器的文件系统到一个tar文件里面。
inspect 是一个通用的命令， 主要是显示一些常见docker对象的信息
[root@ip-172-16-1-4 ec2-user]# docker inspect --help
Usage: docker inspect [OPTIONS] NAME|ID [NAME|ID...]
Return low-level information on Docker objects
Options:
-f, --format string Format the output using the given Go template
-s, --size Display total file sizes if the type is container
--type string Return JSON for specified type比如 我查看一下nginx这个镜像的信息
root@ip-172-16-1-4 ec2-user]# docker inspect nginx
[
{
"Id": "sha256:8cf1bfb43ff5d9b05af9b6b63983440f137c6a08320fa7592197c1474ef30241",
"RepoTags": [
"nginx:latest"
],
"RepoDigests": [
"nginx@sha256:0e188877aa60537d1a1c6484b8c3929cfe09988145327ee47e8e91ddf6f76f5c"
],
"Parent": "",
"Comment": "",
"Created": "2020-07-22T03:23:26.691138735Z",
"Container": "072f077fe42b39ffb92ca368fa5d79be975faa97b33bffb5b5383eb6abfb4838",
"ContainerConfig": {
"Hostname": "072f077fe42b",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"ExposedPorts": {
"80/tcp": {}
},
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"NGINX_VERSION=1.19.1",
"NJS_VERSION=0.4.2",
"PKG_RELEASE=1~buster"
],
"Cmd": [
"/bin/sh",ls 就是显示当前有哪些镜像
[root@ip-172-16-1-4 ec2-user]# docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
nginx latest 8cf1bfb43ff5 2 days ago 132MB
nginx 1.17 9beeba249f3e 2 months ago 127MBsave 和load 相对应，一个是把镜像和相关的资源打包到一个tar文件里面，一个是把这些资源再加载回来。他们的使用场景可以用于备份，或者把镜像拷贝到其他地方使用。
[root@ip-172-16-1-4 ec2-user]# docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
nginx latest 8cf1bfb43ff5 2 days ago 132MB
nginx 1.17 9beeba249f3e 2 months ago 127MB
[root@ip-172-16-1-4 ec2-user]# docker image save 8cf1bfb43ff5 > nginx.tar
[root@ip-172-16-1-4 ec2-user]# du nginx.tar -h
131M nginx.tar生成之后，我来尝试删除一下现有的镜像，他会提示报错，因为我有个容器关联着这个镜像
[root@ip-172-16-1-4 ec2-user]# docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
nginx latest 8cf1bfb43ff5 2 days ago 132MB
nginx 1.17 9beeba249f3e 2 months ago 127MB
[root@ip-172-16-1-4 ec2-user]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
34eef288fd4b nginx "/docker-entrypoint.…" 23 hours ago Up 23 hours 0.0.0.0:8080->80/tcp focused_grothendieck
[root@ip-172-16-1-4 ec2-user]# docker image rm 8cf1bfb43ff5
Error response from daemon: conflict: unable to delete 8cf1bfb43ff5 (cannot be forced) - image is being used by running container 34eef288fd4b
[root@ip-172-16-1-4 ec2-user]#强制关掉正在运行的容器
[root@ip-172-16-1-4 ec2-user]# docker stop $(docker ps -a -q)
34eef288fd4b现在就可以删除镜像了
[root@ip-172-16-1-4 ec2-user]# docker image rm 8cf1bfb43ff5
Error response from daemon: conflict: unable to delete 8cf1bfb43ff5 (must be forced) - image is being used by stopped container 34eef288fd4b
[root@ip-172-16-1-4 ec2-user]# docker image rm 8cf1bfb43ff5 -f
Untagged: nginx:latest
Untagged: nginx@sha256:0e188877aa60537d1a1c6484b8c3929cfe09988145327ee47e8e91ddf6f76f5c
Deleted: sha256:8cf1bfb43ff5d9b05af9b6b63983440f137c6a08320fa7592197c1474ef30241
[root@ip-172-16-1-4 ec2-user]# docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
nginx 1.17 9beeba249f3e 2 months ago 127MBpull 和 push 相对，一个是下载镜像，一个是上传镜像。当我们直接调用 docker run的时候，他会尝试从本地找对应的镜像来创建容器，如果本地没有，那么会自动下载。当然我们也可以 用 pull先下载之后，在创建容器。
[root@ip-172-16-1-4 ec2-user]# docker image pull nginx
Using default tag: latest
latest: Pulling from library/nginx
6ec8c9369e08: Already exists
d3cb09a117e5: Already exists
7ef2f1459687: Already exists
e4d1bf8c9482: Already exists
795301d236d7: Already exists
Digest: sha256:0e188877aa60537d1a1c6484b8c3929cfe09988145327ee47e8e91ddf6f76f5c
Status: Downloaded newer image for nginx:latest
docker.io/library/nginx:latestprune
这个单词的本意是修剪枝叶，他的作用也差不多。 有的时候，镜像可能会出现问题，导致名字变成none，这样的镜像是有问题的，prune可以直接删掉。有的时候，镜像没有连接到任何容器，为了节约空间，我们也可以把这些镜像自动批量删掉。
[root@ip-172-16-1-4 ec2-user]# docker image prune -a
WARNING! This will remove all images without at least one container associated to them.
Are you sure you want to continue? [y/N] y
Deleted Images:
untagged: nginx:1.17
untagged: nginx@sha256:6fff55753e3b34e36e24e37039ee9eae1fe38a6420d8ae16ef37c92d1eb26699
deleted: sha256:9beeba249f3ee158d3e495a6ac25c5667ae2de8a43ac2a8bfd2bf687a58c06c9
deleted: sha256:8fb6373b4cca3383756d7fd7843dd92f95827e5f2913609e09a9621dcddb3752
deleted: sha256:8b09841626797a03a9fe5e73aa38aeacf9ff0ce85a3004236ff35234eec3b35c
deleted: sha256:ffc9b21953f4cd7956cdf532a5db04ff0a2daa7475ad796f1bad58cfbaf77a07
Total reclaimed space: 126.8MB