Docker - Docker Image及Image指令詳解

什麼是鏡像（Image）

Docker鏡像（Docker Image）就是一個隻讀的模闆。比如，一個鏡像可以包含一個完整的Ubuntu作業系統環境。鏡像可以用來建立Docker容器。

在Docker的術語裡，一個隻讀層被稱為鏡像，一個鏡像是永遠不會變的。

由于Docker使用一個統一檔案系統，Docker程序認為整個檔案系統是以讀寫方式挂載的。但是所有的變更都發生在頂層的可寫層，而下層的原始的隻讀鏡像檔案并未變化。由于鏡像不可寫，是以鏡像是無狀态的。

父鏡像

每一個鏡像都可能依賴于由一個或多個下層鏡像組成的另一個鏡像。我們有時說，下層那個鏡像是上層鏡像的父鏡像。而沒有任何父鏡像的鏡像，謂之基礎鏡像（Base Image）。

可以看一下這篇部落格，會讓你對Docker的整體架構有一個很清晰的了解：Docker - 這應該就是你想要的Docker架構分析。

Docker Image Help

通過該指令可以檢視Image下有哪些指令。

docker image help

[root@izoq008ryseuupz ~]# docker image help

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

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

通過

docker image COMMAND --help

來知道每一個Image指令的詳細資訊。

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

Docker Image LS

docker image ls --help

[root@izoq008ryseuupz ~]# docker image ls --help

Usage:  docker image ls [OPTIONS] [REPOSITORY[:TAG]]

List images

Aliases:
  ls, images, list

Options:
  -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的關鍵資訊。

[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

是一樣的效果。

比如

docker image ls -q

，就隻輸出Image的IMAGE ID 。

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

其他的指令選項可以自己試一試。

Docker Image Pull

拉取鏡像。

docker image pull --help

[root@izoq008ryseuupz ~]# docker image pull --help

Usage:  docker image pull [OPTIONS] NAME[:TAG|@DIGEST]

Pull an image or a repository from a registry

Options:
  -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

鏡像。

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

鏡像，隻想要輸出

pull

的簡要資訊，不輸出

pull

的詳細資訊，如

Downloading

的進度。

docker image pull -q centos:6

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

其他的指令選項可以自己試一試。

Docker Image Prune

此指令會把所有未使用的鏡像進行删除（

Remove unused images

），慎用！

docker image prune --help

[root@izoq008ryseuupz ~]# docker image prune --help

Usage:  docker image prune [OPTIONS]

Remove unused images

Options:
  -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

删除指定鏡像。

docker image rm --help

[root@izoq008ryseuupz ~]# docker image rm --help

Usage:  docker image rm [OPTIONS] IMAGE [IMAGE...]

Remove one or more images

Aliases:
  rm, rmi, remove

Options:
  -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

強制删除

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

其他的指令選項可以自己試一試。

Docker Image Tag

對原有鏡像打

tag

，會生成新鏡像。

docker image tag --help

[root@izoq008ryseuupz ~]# docker image tag --help

Usage:  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

儲存鏡像。

docker image save --help

[root@izoq008ryseuupz ~]# docker image save --help

Usage:  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   #儲存到目前目錄
[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 #儲存到别的目錄
[root@izoq008ryseuupz ~]# ls /usr/kaven*
/usr/kaven.blog.tar

Docker Image Load

加載鏡像。

docker image load --help

[root@izoq008ryseuupz ~]# docker image load --help

Usage:  docker image load [OPTIONS]

Load an image from a tar archive or STDIN

Options:
  -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

其他的指令選項可以自己試一試。

Docker Image History

顯示鏡像的操作曆史。

docker image history  --help

[root@izoq008ryseuupz ~]# docker image history  --help

Usage:  docker image history [OPTIONS] IMAGE

Show the history of an image

Options:
      --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

隻想展示鏡像操作曆史的簡要資訊（IMAGE）。

docker image history -q centos:6

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

其他的指令選項可以自己試一試。

Docker Image Inspect

顯示鏡像的詳細資訊。

docker image inspect --help

[root@izoq008ryseuupz ~]# docker image inspect --help

Usage:  docker image inspect [OPTIONS] IMAGE [IMAGE...]

Display detailed information on one or more images

Options:
  -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"
        }
    }
]

其他的指令選項可以自己試一試。

Docker Image Import

從歸檔檔案中建立鏡像。

docker image import --help

[root@izoq008ryseuupz ~]# docker image import --help

Usage:  docker image import [OPTIONS] file|URL|- [REPOSITORY[:TAG]]

Import the contents from a tarball to create a filesystem image

Options:
  -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

其他的指令選項可以自己試一試。

Docker Image Push

上傳鏡像到倉庫。

docker image push --help

[root@izoq008ryseuupz ~]# docker image push --help

Usage:  docker image push [OPTIONS] NAME[:TAG]

Push an image or a repository to a registry

Options:
      --disable-content-trust   Skip image signing (default true)

Docker Image Build

建立鏡像。

docker image build --help

[root@izoq008ryseuupz ~]# docker image build --help

Usage:  docker image build [OPTIONS] PATH | URL | -

Build an image from a Dockerfile

Options:
      --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 [])

這裡會介紹将一個簡單的C語言程式，Build成一個Image。

先在目前目錄下建立一個

hello.c

程式。

vim hello.c

程式如下：

#include<stdio.h>

int main()
{
  printf("hello kaven\n");
  printf("this is docker\n");
}

不知道怎麼退出VIM，可以看一下這篇部落格：怎麼儲存退出 vim 編輯。

[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

在目前目錄下建立

Dockerfile

。

vim Dockerfile

輸入：

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

現在看不懂沒關系，自己跟着體驗一次，之後的部落格會詳細講解這些

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

這樣

kaven/hello:v1

就有了。

Docker - Docker Image及Image指令詳解