简介 镜像是Docker的三大核心概念之一。
获取镜像 镜像是Docker运行容器的前提。 [root@gavin ~]# sudo docker pull ubuntu Using default tag: latest latest: Pulling from library/ubuntu 5b7339215d1d: Pull complete 14ca88e9f672: Pull complete a31c3b1caad4: Pull complete b054a26005b7: Pull complete Digest: sha256:9b1702dcfe32c873a770a32cfd306dd7fc1c4fd134adfb783db68defc8894b3c Status: Downloaded newer image for ubuntu:latest 该命令实际上下载的就是ubuntu:latest镜像,目前最新的18.04版本的镜像。 [root@gavin ~]# sudo docker pull ubuntu:18.04 18.04: Pulling from library/ubuntu Digest: sha256:9b1702dcfe32c873a770a32cfd306dd7fc1c4fd134adfb783db68defc8894b3c Status: Downloaded newer image for ubuntu:18.04 上面两条命令实际上都相当于sudo docker pull registry.hub./ubuntu:latest命令,即从默认的注册服务器registry.hub.中的ubuntu仓库来下载标记为latest的镜像。 下载镜像到本地后,即可随时使用该镜像了,例如利用该镜像创建一个容器,在其中运行bash应用。 [root@gavin ~]# sudo docker run -t -t ubuntu:latest /bin/bash root@74bf842f3c6c:/#
查看镜像信息 使用docker images命令可以列出本地主机上已有的镜像。 [root@gavin ~]# sudo docker images REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu 18.04 4c108a37151f 2 weeks ago 64.2MB ubuntu latest 4c108a37151f 2 weeks ago 64.2MB 在列出信息中,可以看到有几个字段信息:
其中镜像的ID信息十分重要,它唯一标识了镜像。 [root@gavin ~]# sudo docker tag ubuntu:latest ubuntu:v1.0 再次使用docker images列出本地主机上镜像信息,可以看到多了一个ubuntu:v1.0标签的镜像。 [root@gavin ~]# sudo docker images REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu 18.04 4c108a37151f 2 weeks ago 64.2MB ubuntu latest 4c108a37151f 2 weeks ago 64.2MB ubuntu v1.0 4c108a37151f 2 weeks ago 64.2MB 细心的读者可能会注意到,这些不同标签的镜像的ID是完全一致的,说明它们实际上指向了同一个镜像文件,只是别名不同而已。标签在这里起到了引用或快捷方式的作用。 [root@gavin ~]# sudo docker inspect 4c108a37151f [ { "Id": "sha256:4c108a37151f54439950335c409802e948883e00c93fdb751d206c9a9674c1f6", "RepoTags": [ "ubuntu:18.04", "ubuntu:latest", "ubuntu:v1.0" ], "RepoDigests": [ "ubuntu@sha256:9b1702dcfe32c873a770a32cfd306dd7fc1c4fd134adfb783db68defc8894b3c" ], "Parent": "", "Comment": "", "Created": "2019-06-18T22:51:38.340092056Z", "Container": "fdea049ea807b599050e885a88784e009ed78ebcc4d498be93744bb9374c6134", "ContainerConfig": { "Hostname": "fdea049ea807", "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:ae950a0376fe6c4d08fa7ff395f50f4a909e26e9f2d865d8641cda024161c6ee", "Volumes": null, "WorkingDir": "", "Entrypoint": null, "OnBuild": null, "Labels": {} }, "DockerVersion": "18.06.1-ce", "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:ae950a0376fe6c4d08fa7ff395f50f4a909e26e9f2d865d8641cda024161c6ee", "Volumes": null, "WorkingDir": "", "Entrypoint": null, "OnBuild": null, "Labels": null }, "Architecture": "amd64", "Os": "linux", "Size": 64184378, "VirtualSize": 64184378, "GraphDriver": { "Data": { "LowerDir": "/var/lib/docker/overlay2/c2dab2bd224b9fa08454dd83047c951dc083d7e66cbd3bc121525f90d91aa3f8/diff:/var/lib/docker/overlay2/6247f7d6c45adb4475889cfa641dfc3c917de3a501d7e29c09833bdb98acf3de/diff:/var/lib/docker/overlay2/2adcd34ff16da9a82706938907f6f2bcee53ec5e0e7e6d6b8ee90eea80d635e4/diff", "MergedDir": "/var/lib/docker/overlay2/4d6fe2c8be4a0d1a7afc7a648c8be8dfbda2eb1b621db2b3a2832c5e3aa659f9/merged", "UpperDir": "/var/lib/docker/overlay2/4d6fe2c8be4a0d1a7afc7a648c8be8dfbda2eb1b621db2b3a2832c5e3aa659f9/diff", "WorkDir": "/var/lib/docker/overlay2/4d6fe2c8be4a0d1a7afc7a648c8be8dfbda2eb1b621db2b3a2832c5e3aa659f9/work" }, "Name": "overlay2" }, "RootFS": { "Type": "layers", "Layers": [ "sha256:ba9de9d8475e7f5e40086358a1353b3cc080994fc6d31e4272dd3acb69b0151e", "sha256:fbd2732ad777cb5db2515fa62b6122b797be233d01db02e0a19e5d894688cad6", "sha256:dda1518598187bf87704acc22aa0ec2a67d9e7835c24346dfca118ab42c5cd0b", "sha256:75e70aa52609fdbd63b58d46d6f7c20470062e1c9bb75616f7703a358a61e5ca" ] }, "Metadata": { "LastTagTime": "2019-07-09T18:06:36.890136591 04:00" } } ] docker inspect 命令返回的是一个JSON格式的消息,如果我们只要其中一项内容时,可以使用-f参数来指定,例如,获取镜像的Architecture信息: [root@gavin ~]# sudo docker inspect -f {{".Architecture"}} 4c108a37151f amd64
搜寻镜像使用docker search命令可以搜索远端仓库中共享的镜像,默认搜索Docker Hub官方仓库中的镜像。用法为docker search TERM,支持的参数包括:
例如,搜索带mysql关键字的镜像如下所示: [root@gavin ~]# sudo docker search mysql NAME DESCRIPTION STARS OFFICIAL AUTOMATED mysql MySQL is a widely used, open-source relation… 8364 [OK] mariadb MariaDB is a community-developed fork of MyS… 2866 [OK] mysql/mysql-server Optimized MySQL Server Docker images. Create… 623 [OK] percona Percona Server is a fork of the MySQL relati… 438 [OK] centurylink/mysql Image containing mysql. Optimized to be link… 60 [OK] centos/mysql-57-centos7 MySQL 5.7 SQL database server 57 mysql/mysql-cluster Experimental MySQL Cluster Docker images. Cr… 46 deitch/mysql-backup Automated and scheduled mysql database dumps… 39 [OK] tutum/mysql Base docker image to run a MySQL database se… 32 schickling/mysql-backup-s3 Backup MySQL to S3 (supports periodic backup… 28 [OK] bitnami/mysql Bitnami MySQL Docker Image 27 [OK] linuxserver/mysql A Mysql container, brought to you by LinuxSe… 20 prom/mysqld-exporter 19 [OK] centos/mysql-56-centos7 MySQL 5.6 SQL database server 15 mysql/mysql-router MySQL Router provides transparent routing be… 12 circleci/mysql MySQL is a widely used, open-source relation… 12 arey/mysql-client Run a MySQL client from a docker container 10 [OK] yloeffler/mysql-backup This image runs mysqldump to backup data usi… 6 [OK] openshift/mysql-55-centos7 DEPRECATED: A Centos7 based MySQL v5.5 image… 6 fradelg/mysql-cron-backup MySQL/MariaDB database backup using cron tas… 4 [OK] genschsa/mysql-employees MySQL Employee Sample Database 2 [OK] jelastic/mysql An image of the MySQL database server mainta… 1 monasca/mysql-init A minimal decoupled init container for mysql 0 widdpim/mysql-client Dockerized MySQL Client (5.7) including Curl… 0 [OK] ansibleplaybookbundle/mysql-apb An APB which deploys RHSCL MySQL 0 [OK] 可以看到返回了很多包含关键字的镜像,其中包括镜像名字、描述、星级(表示该镜像的受欢迎程度)、是否官方创建、是否自动创建等。
删除镜像使用镜像的标签删除镜像 使用docker rmi命令可以删除镜像,命令格式为docker rmi IMAGE [IMAGE...],其中IMAGE可以为标签或ID。 [root@gavin ~]# sudo docker rmi ubuntu:v1.0 Untagged: ubuntu:v1.0 读者可能会担心,本地的ubuntu:latest镜像是否会受到此命令的影响。无需担心,当同一个镜像拥有多个标签的时候,docker rmi命令只是删除了该镜像多个标签中的指定标签而已,并不影响镜像文件。因此上述操作相当于只是删除了镜像4c108a37151f的一个标签而已。 [root@gavin ~]# sudo docker images REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu 18.04 4c108a37151f 2 weeks ago 64.2MB ubuntu latest 4c108a37151f 2 weeks ago 64.2MB 但当镜像只剩下一个标签的时候就要小心了,此时再使用docker rmi命令会彻底删除该镜像。 [root@gavin ~]# sudo docker rmi mysql:latest Untagged: mysql:latest Untagged: mysql@sha256:415ac63da0ae6725d5aefc9669a1c02f39a00c574fdbc478dfd08db1e97c8f1b Deleted: sha256:c7109f74d339896c8e1a7526224f10a3197e7baf674ff03acbab387aa027882a Deleted: sha256:35d60530f024aa75c91a123a69099f7f6eaf5ad7001bb983f427f674980d8482 Deleted: sha256:49d8bb533eee600076e3a513a203ee24044673fcef0c1b79e088b2ba43db2c17 Deleted: sha256:2e7d501ae7df8ee0eca0fe0b16c6e9fad9a3664811445f38f32636b47366eec3 Deleted: sha256:6a362ed9781f7b3f0c63b061dfb0f14d9ba10d021df10712a131158c103b0d18 Deleted: sha256:3e58b58898622709169f72e7fa20244e084316f3ee66142728bce3f35bb9538b Deleted: sha256:4beb9add2b61bbae54c13e9d9f374b1fe8573226c2fe889bdd5dc8eed19ffbc1 Deleted: sha256:b3a6af4f3db06bbe8f661019f7dbc354b5e63318fca01d8f1e6218f0afbaa5eb Deleted: sha256:037818566b488757260ae3d0064fbf6e47365cd08dc6409b7a018a512ef17f25 Deleted: sha256:000ec65531a617f550ee04f67c875b70f4b395af00b5f5bb7ed480b17078bc0b Deleted: sha256:11d387a2efcce7596530d6be2299b6528b0afe070aba3caf3432ca31c3b0132d Deleted: sha256:a883a9d05facd6220d9251787142b41cc6675f247bc47c94071e665adf65dbbf Deleted: sha256:cf5b3c6798f77b1f78bf4e297b27cfa5b6caa982f04caeb5de7d13c255fd7a1e 使用镜像的ID删除镜像 当使用docker rmi命令后面跟上镜像的ID(也可以是ID能进行区分的部分前缀串)时,会先尝试删除所有指向该镜像的标签,然后删除该镜像文件本身。 [root@gavin ~]# sudo docker run ubuntu:latest echo 'hello docker' hello docker 使用docker ps -a命令可以看到本机上存在的所有容器: [root@gavin ~]# sudo docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES f062ef2957f1 ubuntu:latest "echo 'hello docker'" 2 minutes ago Exited (0) 2 minutes ago sleepy_euler 可以看到,后台存在一个退出状态的容器,是刚基于ubuntu:latest镜像创建的。 [root@gavin ~]# sudo docker rmi ubuntu:latest Untagged: ubuntu:latest 结果我们这里删除成功了,原因是存在相同ID的镜像(ubuntu:18.04,ubuntu:latest),前面只是删除了一个tag(标签),这里我们再删除ubuntu:18.04 [root@gavin ~]# sudo docker rmi ubuntu:18.04 Error response from daemon: conflict: unable to remove repository reference "ubuntu:18.04" (must force) - container f062ef2957f1 is using its referenced image 4c108a37151f 果不其然提示有容器正在引用,无法删除。 [root@gavin ~]# sudo docker rmi -f ubuntu:18.04 Untagged: ubuntu:18.04 Untagged: ubuntu@sha256:9b1702dcfe32c873a770a32cfd306dd7fc1c4fd134adfb783db68defc8894b3c Deleted: sha256:4c108a37151f54439950335c409802e948883e00c93fdb751d206c9a9674c1f6 博主不推荐使用-f参数来强制删除一个存在容器依赖的镜像,因为这样往往会造成一些遗留问题。 [root@gavin ~]# sudo docker rm f06 f06 此时再使用ID来删除镜像,此时会正常打印出删除的各层信息: [root@gavin ~]# sudo docker rmi 4c108a37151f Untagged: ubuntu:latest Untagged: ubuntu@sha256:9b1702dcfe32c873a770a32cfd306dd7fc1c4fd134adfb783db68defc8894b3c Deleted: sha256:4c108a37151f54439950335c409802e948883e00c93fdb751d206c9a9674c1f6 Deleted: sha256:7c1abf1dbbfd02a48330a7317ab45a6091d53e2e9cc062f0f3dbd2b7539947a6 Deleted: sha256:5a614dda4a54650168ee2cd30ce2e39576dad5c9a0d1907c02445687b4ea5090 Deleted: sha256:bd042113a73a5c9c6680990740446b7324afb39e243ade3d33bdaa9ffaf8d294 Deleted: sha256:ba9de9d8475e7f5e40086358a1353b3cc080994fc6d31e4272dd3acb69b0151e
创建镜像 创建镜像的方法有三种:基于已有镜像的容器创建、基于本地模板导入、基于Dockerfile创建。 基于已有镜像的容器创建该方法主要是使用docker commit命令,其命令格式为docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]],主要选项包括:
下面将演示如何使用该命令创建一个新镜像。首先,启动一个镜像,并在其中进行修改操作,例如创建一个test文件,之后退出: [root@gavin ~]# sudo docker run -ti ubuntu:18.04 /bin/bash root@e8382cf8c930:/# touch test root@e8382cf8c930:/# exit 记住容器的ID为:e8382cf8c930。 [root@gavin ~]# sudo docker commit -m "Added a new file" -a "Docker Newbee" e8382cf8c930 test:1.0 sha256:a7f06e6700e36df75ad4dfc952bab4861f35edb840f50aeb3b657d8cc27e9403 顺利的话,命令会返回新创建的镜像的ID信息,例如:a7f06e6700e36df75ad4dfc952bab4861f35edb840f50aeb3b657d8cc27e9403 [root@gavin ~]# sudo docker images REPOSITORY TAG IMAGE ID CREATED SIZE test 1.0 a7f06e6700e3 2 minutes ago 64.2MB ubuntu 18.04 4c108a37151f 3 weeks ago 64.2MB 基于本地模板导入 也可以直接从一个操作系统模板文件导入一个镜像。在这里,推荐使用OpenVZ提供的模板来创建。OPENVZ模板的下载地址为https://wiki./Download/templates/precreated。 [root@gavin data]# sudo cat centos-7-x86_64.tar.gz | docker import - centos:7.0 sha256:0c4f10b8e790e76e2b60d4afff42248b04abacfb9918109e8b3dc94d72cafda1 然后查看新导入的镜像,已经在本地存在了: [root@gavin data]# sudo docker images REPOSITORY TAG IMAGE ID CREATED SIZE centos 7.0 0c4f10b8e790 About a minute ago 589MB test 1.0 a7f06e6700e3 16 minutes ago 64.2MB ubuntu 18.04 4c108a37151f 3 weeks ago 64.2MB
存出和存入镜像可以使用docker save和docker load命令来存出和载入镜像。 存出镜像如果要存出镜像到本地文件,可以使用docker save命令。例如,存出本地的ubuntu:18.04镜像为文件 ubuntu_18.04.tar: [root@gavin /]# sudo docker save -o ubuntu_18.04.tar ubuntu:18.04 存入镜像可以使用docker load从存出的本地文件中再导入到本地镜像库,例如从文件ubuntu_18.04.tar导入镜像到本地镜像列表,如下所示: [root@gavin /]# sudo docker load --input ubuntu_18.04.tar 或 [root@gavin /]# sudo docker load < ubuntu_18.04.tar 这将导入镜像以及其相关的元数据信息(包括标签等),可以使用docker images命令进行查看。
上传镜像 可以使用docker push命令上传镜像到仓库,默认上传到DockerHub官方仓库(需要登录),命令格式为docker push NAME[:TAG]。 [root@gavin /]# docker login Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub. to create one. Username: xiaohui1994 Password: WARNING! Your password will be stored unencrypted in /root/.docker/config.json. Configure a credential helper to remove this warning. See https://docs./engine/reference/commandline/login/#credentials-store Login Succeeded [root@gavin /]# sudo docker push xiaohui1994/test:1.0 The push refers to repository [docker.io/xiaohui1994/test] bb817e704dea: Pushed 75e70aa52609: Mounted from library/ubuntu dda151859818: Mounted from library/ubuntu fbd2732ad777: Mounted from library/ubuntu ba9de9d8475e: Mounted from library/ubuntu 1.0: digest: sha256:ec47f750b7827f9e5483a4ac48d12fadf8cfe05b2e7839d0884b1bbacdf70441 size: 1359 此时登录DockerHub可以看到刚上传的镜像:
这篇文章是我学习 Docker 的记录,内容参考自《Docker技术入门与实战》 来源:https://www./content-4-319451.html |
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