Docker - Docker Image及Image命令详解

什么是镜像（Image）

Docker镜像（Docker Image）就是一个只读的模板。比如，一个镜像可以包含一个完整的Ubuntu操作系统环境。镜像可以用来创建Docker容器。

在Docker的术语里，一个只读层被称为镜像，一个镜像是永远不会变的。

由于Docker使用一个统一文件系统，Docker进程认为整个文件系统是以读写方式挂载的。但是所有的变更都发生在顶层的可写层，而下层的原始的只读镜像文件并未变化。由于镜像不可写，所以镜像是无状态的。

父镜像

每一个镜像都可能依赖于由一个或多个下层镜像组成的另一个镜像。我们有时说，下层那个镜像是上层镜像的父镜像。而没有任何父镜像的镜像，谓之基础镜像（Base Image）。

可以看一下这篇博客，会让你对Docker的整体架构有一个很清晰的了解：Docker - 这应该就是你想要的Docker架构分析。

Docker Image Help

通过该命令可以查看Image下有哪些命令。

docker image help

[root@izoq008ryseuupz ~]# docker image helpUsage:   docker image COMMANDManage imagesCommands:build       Build an image from a Dockerfilehistory     Show the history of an imageimport      Import the contents from a tarball to create a filesystem imageinspect     Display detailed information on one or more imagesload        Load an image from a tar archive or STDINls          List imagesprune       Remove unused imagespull        Pull an image or a repository from a registrypush        Push an image or a repository to a registryrm          Remove one or more imagessave        Save one or more images to a tar archive (streamed to STDOUT by default)tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGERun 'docker image COMMAND --help' for more information on a command.

通过docker image COMMAND --help来知道每一个Image命令的详细信息。

Run 'docker image COMMAND --help' for more information on a command.

Docker Image LS

docker image ls --help

[root@izoq008ryseuupz ~]# docker image ls --helpUsage:  docker image ls [OPTIONS] [REPOSITORY[:TAG]]List imagesAliases:ls, images, listOptions:-a, --all             Show all images (default hides intermediate images)--digests         Show digests-f, --filter filter   Filter output based on conditions provided--format string   Pretty-print images using a Go template--no-trunc        Don't truncate output-q, --quiet           Only show numeric IDs

比如docker image ls -a，展示所有Image的关键信息。

[root@izoq008ryseuupz ~]# docker image ls -a
REPOSITORY                                                     TAG                 IMAGE ID            CREATED             SIZE
node                                                           latest              5377c9a2fb1f        5 weeks ago         943MB
openzipkin/zipkin                                              latest              1850194f377c        3 months ago        160MB
rancher/server                                                 stable              98d8bb571885        6 months ago        1.08GB
redis                                                          5.0.7               7eed8df88d3b        8 months ago        98.2MB
hello-world                                                    latest              bf756fb1ae65        10 months ago       13.3kB

docker images、docker image ls和docker image ls -a是一样的效果。

比如docker image ls -q，就只输出Image的IMAGE ID 。

[root@izoq008ryseuupz ~]# docker image ls -q
5377c9a2fb1f
1850194f377c
98d8bb571885
7eed8df88d3b
bf756fb1ae65

其他的命令选项可以自己试一试。

Docker Image Pull

拉取镜像。

docker image pull --help

[root@izoq008ryseuupz ~]# docker image pull --helpUsage:    docker image pull [OPTIONS] NAME[:TAG|@DIGEST]Pull an image or a repository from a registryOptions:-a, --all-tags                Download all tagged images in the repository--disable-content-trust   Skip image verification (default true)--platform string         Set platform if server is multi-platform capable-q, --quiet                   Suppress verbose output

拉取centos:7镜像。

docker image pull centos:7

[root@izoq008ryseuupz ~]# docker image pull centos:7
7: Pulling from library/centos
2d473b07cdd5: Pull complete
Digest: sha256:0f4ec88e21daf75124b8a9e5ca03c37a5e937e0e108a255d890492430789b60e
Status: Downloaded newer image for centos:7
docker.io/library/centos:7

拉取centos:6镜像，只想要输出pull的简要信息，不输出pull的详细信息，如Downloading的进度。

docker image pull -q centos:6

[root@izoq008ryseuupz ~]# docker image pull -q centos:6
docker.io/library/centos:6

其他的命令选项可以自己试一试。

Docker Image Prune

此命令会把所有未使用的镜像进行删除（Remove unused images），慎用！

docker image prune --help

[root@izoq008ryseuupz ~]# docker image prune --helpUsage:   docker image prune [OPTIONS]Remove unused imagesOptions:-a, --all             Remove all unused images, not just dangling ones--filter filter   Provide filter values (e.g. 'until=<timestamp>')-f, --force           Do not prompt for confirmation

docker image prune

[root@izoq008ryseuupz ~]# docker image prune
WARNING! This will remove all dangling images.
Are you sure you want to continue? [y/N] y
Total reclaimed space: 0B

Docker Image RM

删除指定镜像。

docker image rm --help

[root@izoq008ryseuupz ~]# docker image rm --helpUsage:  docker image rm [OPTIONS] IMAGE [IMAGE...]Remove one or more imagesAliases:rm, rmi, removeOptions:-f, --force      Force removal of the image--no-prune   Do not delete untagged parents

删除centos:7。

docker image rm centos:7

[root@izoq008ryseuupz ~]# docker image rm centos:7
Untagged: centos:7
Untagged: centos@sha256:0f4ec88e21daf75124b8a9e5ca03c37a5e937e0e108a255d890492430789b60e
Deleted: sha256:8652b9f0cb4c0599575e5a003f5906876e10c1ceb2ab9fe1786712dac14a50cf
Deleted: sha256:174f5685490326fc0a1c0f5570b8663732189b327007e47ff13d2ca59673db02

强制删除centos:6。

docker image rm -f centos:6

[root@izoq008ryseuupz ~]# docker image rm -f centos:6
Untagged: centos:6
Untagged: centos@sha256:dec8f471302de43f4cfcf82f56d99a5227b5ea1aa6d02fa56344986e1f4610e7
Deleted: sha256:d0957ffdf8a2ea8c8925903862b65a1b6850dbb019f88d45e927d3d5a3fa0c31
Deleted: sha256:af6bf1987c2eb07d73f33836b0d8fd825d7c785273526b077e46780e8b4b2ae9

其他的命令选项可以自己试一试。

Docker Image Tag

对原有镜像打tag，会生成新镜像。

docker image tag --help

[root@izoq008ryseuupz ~]# docker image tag --helpUsage: docker image tag SOURCE_IMAGE[:TAG] TARGET_IMAGE[:TAG]Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE

docker image tag centos:6 centos:kaven.blog

Docker Image Save

保存镜像。

docker image save --help

[root@izoq008ryseuupz ~]# docker image save --helpUsage:    docker image save [OPTIONS] IMAGE [IMAGE...]Save one or more images to a tar archive (streamed to STDOUT by default)Options:-o, --output string   Write to a file, instead of STDOUT

docker image save centos:kaven.blog > kaven.blog.tar

[root@izoq008ryseuupz ~]# docker image save centos:kaven.blog > kaven.blog.tar   #保存到当前目录
[root@izoq008ryseuupz ~]# ls kaven*
kaven.blog.tar

docker image save centos:kaven.blog -o /usr/kaven.blog.tar

[root@izoq008ryseuupz ~]# docker image save centos:kaven.blog -o /usr/kaven.blog.tar #保存到别的目录
[root@izoq008ryseuupz ~]# ls /usr/kaven*
/usr/kaven.blog.tar

Docker Image Load

加载镜像。

docker image load --help

[root@izoq008ryseuupz ~]# docker image load --helpUsage:    docker image load [OPTIONS]Load an image from a tar archive or STDINOptions:-i, --input string   Read from tar archive file, instead of STDIN-q, --quiet          Suppress the load output

docker image load < kaven.blog.tar

[root@izoq008ryseuupz ~]# docker image rm centos:kaven.blog
Untagged: centos:kaven.blog
[root@izoq008ryseuupz ~]# docker image load < kaven.blog.tar
Loaded image: centos:kaven.blog

docker image load -i /usr/kaven.blog.tar

[root@izoq008ryseuupz ~]# docker image rm centos:kaven.blog
Untagged: centos:kaven.blog
[root@izoq008ryseuupz ~]# docker image load -i /usr/kaven.blog.tar
Loaded image: centos:kaven.blog

其他的命令选项可以自己试一试。

Docker Image History

显示镜像的操作历史。

docker image history  --help

[root@izoq008ryseuupz ~]# docker image history  --helpUsage:    docker image history [OPTIONS] IMAGEShow the history of an imageOptions:--format string   Pretty-print images using a Go template-H, --human           Print sizes and dates in human readable format (default true)--no-trunc        Don't truncate output-q, --quiet           Only show numeric IDs

docker image history centos:kaven.blog

[root@izoq008ryseuupz ~]# docker image history centos:kaven.blog
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
d0957ffdf8a2        20 months ago       /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B
<missing>           20 months ago       /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B
<missing>           20 months ago       /bin/sh -c #(nop) ADD file:0065316a41144e95b…   194MB
<missing>           2 years ago         /bin/sh -c #(nop)  MAINTAINER https://github…   0B

只想展示镜像操作历史的简要信息（IMAGE）。

docker image history -q centos:6

[root@izoq008ryseuupz ~]# docker image history -q centos:6
d0957ffdf8a2
<missing>
<missing>
<missing>

其他的命令选项可以自己试一试。

Docker Image Inspect

显示镜像的详细信息。

docker image inspect --help

[root@izoq008ryseuupz ~]# docker image inspect --helpUsage: docker image inspect [OPTIONS] IMAGE [IMAGE...]Display detailed information on one or more imagesOptions:-f, --format string   Format the output using the given Go template

docker image inspect centos:6

[root@izoq008ryseuupz ~]# docker image inspect centos:6
[{"Id": "sha256:d0957ffdf8a2ea8c8925903862b65a1b6850dbb019f88d45e927d3d5a3fa0c31","RepoTags": ["centos:6","centos:kaven.blog"],"RepoDigests": ["centos@sha256:dec8f471302de43f4cfcf82f56d99a5227b5ea1aa6d02fa56344986e1f4610e7"],"Parent": "","Comment": "","Created": "2019-03-14T21:20:11.486358099Z","Container": "d519f3e5c41d16388d3fba0dac626427b21deb98cce150dee80c180b9baf9435","ContainerConfig": {"Hostname": "d519f3e5c41d","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": "sha256:143abcd43bce45f4fd9ba51c7361051d7ea9e9e1eadb66e5c94a9c1b7754524f","Volumes": null,"WorkingDir": "","Entrypoint": null,"OnBuild": null,"Labels": {"org.label-schema.build-date": "20181006","org.label-schema.license": "GPLv2","org.label-schema.name": "CentOS Base Image","org.label-schema.schema-version": "1.0","org.label-schema.vendor": "CentOS"}},"DockerVersion": "18.06.1-ce","Author": "https://github.com/CentOS/sig-cloud-instance-images","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": "sha256:143abcd43bce45f4fd9ba51c7361051d7ea9e9e1eadb66e5c94a9c1b7754524f","Volumes": null,"WorkingDir": "","Entrypoint": null,"OnBuild": null,"Labels": {"org.label-schema.build-date": "20181006","org.label-schema.license": "GPLv2","org.label-schema.name": "CentOS Base Image","org.label-schema.schema-version": "1.0","org.label-schema.vendor": "CentOS"}},"Architecture": "amd64","Os": "linux","Size": 193901906,"VirtualSize": 193901906,"GraphDriver": {"Data": {"MergedDir": "/var/lib/docker/overlay2/ae0f8ac6c397e63561b52142c4e945909b8af2351d28e5af66f3490ff7078587/merged","UpperDir": "/var/lib/docker/overlay2/ae0f8ac6c397e63561b52142c4e945909b8af2351d28e5af66f3490ff7078587/diff","WorkDir": "/var/lib/docker/overlay2/ae0f8ac6c397e63561b52142c4e945909b8af2351d28e5af66f3490ff7078587/work"},"Name": "overlay2"},"RootFS": {"Type": "layers","Layers": ["sha256:af6bf1987c2eb07d73f33836b0d8fd825d7c785273526b077e46780e8b4b2ae9"]},"Metadata": {"LastTagTime": "2020-11-22T11:46:01.910880961+08:00"}}
]

其他的命令选项可以自己试一试。

Docker Image Import

从归档文件中创建镜像。

docker image import --help

[root@izoq008ryseuupz ~]# docker image import --helpUsage:  docker image import [OPTIONS] file|URL|- [REPOSITORY[:TAG]]Import the contents from a tarball to create a filesystem imageOptions:-c, --change list       Apply Dockerfile instruction to the created image-m, --message string    Set commit message for imported image--platform string   Set platform if server is multi-platform capable

docker image import  kaven.blog.tar centos:6.kaven

[root@izoq008ryseuupz ~]# docker image import  kaven.blog.tar centos:6.kaven
sha256:3a568400d73096f71c5f5165f110414bb83e8024bca2ee3eea77336a194e920f

其他的命令选项可以自己试一试。

Docker Image Push

上传镜像到仓库。

docker image push --help

[root@izoq008ryseuupz ~]# docker image push --helpUsage:    docker image push [OPTIONS] NAME[:TAG]Push an image or a repository to a registryOptions:--disable-content-trust   Skip image signing (default true)

Docker Image Build

创建镜像。

docker image build --help

[root@izoq008ryseuupz ~]# docker image build --helpUsage:   docker image build [OPTIONS] PATH | URL | -Build an image from a DockerfileOptions:--add-host list           Add a custom host-to-IP mapping (host:ip)--build-arg list          Set build-time variables--cache-from strings      Images to consider as cache sources--cgroup-parent string    Optional parent cgroup for the container--compress                Compress the build context using gzip--cpu-period int          Limit the CPU CFS (Completely Fair Scheduler) period--cpu-quota int           Limit the CPU CFS (Completely Fair Scheduler) quota-c, --cpu-shares int          CPU shares (relative weight)--cpuset-cpus string      CPUs in which to allow execution (0-3, 0,1)--cpuset-mems string      MEMs in which to allow execution (0-3, 0,1)--disable-content-trust   Skip image verification (default true)-f, --file string             Name of the Dockerfile (Default is 'PATH/Dockerfile')--force-rm                Always remove intermediate containers--iidfile string          Write the image ID to the file--isolation string        Container isolation technology--label list              Set metadata for an image-m, --memory bytes            Memory limit--memory-swap bytes       Swap limit equal to memory plus swap: '-1' to enable unlimited swap--network string          Set the networking mode for the RUN instructions during build (default "default")--no-cache                Do not use cache when building the image-o, --output stringArray      Output destination (format: type=local,dest=path)--platform string         Set platform if server is multi-platform capable--progress string         Set type of progress output (auto, plain, tty). Use plain to show container output (default "auto")--pull                    Always attempt to pull a newer version of the image-q, --quiet                   Suppress the build output and print image ID on success--rm                      Remove intermediate containers after a successful build (default true)--secret stringArray      Secret file to expose to the build (only if BuildKit enabled): id=mysecret,src=/local/secret--security-opt strings    Security options--shm-size bytes          Size of /dev/shm--squash                  Squash newly built layers into a single new layer--ssh stringArray         SSH agent socket or keys to expose to the build (only if BuildKit enabled) (format: default|<id>[=<socket>|<key>[,<key>]])--stream                  Stream attaches to server to negotiate build context-t, --tag list                Name and optionally a tag in the 'name:tag' format--target string           Set the target build stage to build.--ulimit ulimit           Ulimit options (default [])

这里会介绍将一个简单的C语言程序，Build成一个Image。

先在当前目录下创建一个hello.c程序。

vim hello.c

程序如下：

#include<stdio.h>int main()
{printf("hello kaven\n");printf("this is docker\n");
}

不知道怎么退出VIM，可以看一下这篇博客：怎么保存退出 vim 编辑。

[root@izoq008ryseuupz ~]# ls
hello.c  kaven.blog.tar  logs  mall.jar
[root@izoq008ryseuupz ~]# gcc hello.c -o hello
[root@izoq008ryseuupz ~]# ls
hello  hello.c  kaven.blog.tar  logs  mall.jar
[root@izoq008ryseuupz ~]# ./hello
hello kaven
this is docker

在当前目录下创建Dockerfile。

vim Dockerfile

输入：

FROM scratch
ADD hello /
CMD ["/hello"]

现在看不懂没关系，自己跟着体验一次，之后的博客会详细讲解这些Dockerfile操作。

docker image build -t kaven/hello:v1 .

[root@izoq008ryseuupz ~]# docker image build -t kaven/hello:v1 .
Sending build context to Docker daemon  564.4MB
Step 1/3 : FROM scratch--->
Step 2/3 : ADD hello /---> 5d49f50c725b
Step 3/3 : CMD ["/hello"]---> Running in b0b3bdce9078
Removing intermediate container b0b3bdce9078---> b1013ca7925d
Successfully built b1013ca7925d
Successfully tagged kaven/hello:v1

这样kaven/hello:v1就有了。

Docker Image及Image命令详解就介绍到这里。

写博客是博主记录自己的学习过程，如果有错误，请指正，谢谢！