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docker-anpine镜像介绍

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镜像管理

镜像,即创建容器的模版,含有启动容器所需要的文件系统及所需要的内容,因此镜像主要用于方便和快速的创建并启动容器

镜像含里面是一层层的文件系统,叫做 Union FS(联合文件系统),联合文件系统,可以将几层目录挂载到一起(就像千层饼,洋葱头,俄罗斯套娃一样),形成一个虚拟文件系统,虚拟文件系统的目录结构就像普通 linux 的目录结构一样,镜像通过这些文件再加上宿主机的内核共同提供了一个 linux 的虚拟环境,每一层文件系统叫做一层 layer,联合文件系统可以对每一层文件系统设置三种权限,只读(readonly)、读写(readwrite)和写出(whiteout-able),但是镜像中每一层文件系统都是只读的,构建镜像的时候,从一个最基本的操作系统开始,每个构建提交的操作都相当于做一层的修改,增加了一层文件系统,一层层往上叠加,上层的修改会覆盖底层该位置的可见性,这也很容易理解,就像上层把底层遮住了一样,当使用镜像的时候,我们只会看到一个完全的整体,不知道里面有几层也不需要知道里面有几层,结构如下:

docker-镜像管理插图

一个典型的 Linux文件系统由bootfs和rootfs两部分组成,bootfs(boot file system) 主要包含bootloader和kernel,bootloader主要用于引导加载 kernel,当 kernel 被加载到内存中后bootfs会被umount 掉,rootfs (root file system) 包含的就是典型 Linux 系统中的/dev,/proc,/bin,/etc 等标准目录和文件,下图就是镜像中最基础的两层结构,不同的 linux 发行版(如 ubuntu 和 CentOS ) 在 rootfs 这一层会有所区别。

一般的镜像通常都比较小,官方提供的Ubuntu镜像只有60MB多点,而CentOS基础镜像也只有200MB左右,一些其他版本的镜像甚至只有几MB,比如:busybox 才1.22MB,alpine镜像也只有5M左右。镜像直接调用宿主机的内核,镜像中只提供rootfs,也就是只需要包括最基本的命令、工具和程序库就可以了。

下图就是有两个不同的镜像在一个宿主机内核上实现不同的rootfs。

docker-镜像管理插图(1)

容器、镜像父镜像:

docker-镜像管理插图(2)

docker 命令是最常使用的docker 客户端命令,其后面可以加不同的参数以实现响应的功能,常用的命令如下:

[root@ubuntu1804 ~]#docker --help

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:
      --config string      Location of client config files (default "/root/.docker")
  -c, --context string     Name of the context to use to connect to the daemon (overrides DOCKER_HOST env var and default
                           context set with "docker context use")
  -D, --debug              Enable debug mode
  -H, --host list          Daemon socket(s) to connect to
  -l, --log-level string   Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
      --tls                Use TLS; implied by --tlsverify
      --tlscacert string   Trust certs signed only by this CA (default "/root/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default "/root/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default "/root/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Management Commands:
  builder     Manage builds
  config      Manage Docker configs
  container   Manage containers
  context     Manage contexts
  engine      Manage the docker engine
  image       Manage images
  network     Manage networks
  node        Manage Swarm nodes
  plugin      Manage plugins
  secret      Manage Docker secrets
  service     Manage services
  stack       Manage Docker stacks
  swarm       Manage Swarm
  system      Manage Docker
  trust       Manage trust on Docker images
  volume      Manage volumes

Commands:
  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

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

范例:查看镜像的分层结构

[root@ubuntu1804 ~]#docker pull nginx 
Using default tag: latest
latest: Pulling from library/nginx
8ec398bc0356: Pull complete 
a53c868fbde7: Pull complete 
79daf9dd140d: Pull complete 
Digest: sha256:70821e443be75ea38bdf52a974fd2271babd5875b2b1964f05025981c75a6717
Status: Downloaded newer image for nginx:latest
docker.io/library/nginx:latest
[root@ubuntu1804 ~]#docker save nginx -o nginx.tar.gz
[root@ubuntu1804 ~]#docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
nginx               latest              5ad3bd0e67a9        3 days ago          127MB
alpine              3.11.3              e7d92cdc71fe        7 days ago          5.59MB
centos              centos8.1.1911      470671670cac        7 days ago          237MB
busybox             latest              6d5fcfe5ff17        4 weeks ago         1.22MB
hello-world         latest              fce289e99eb9        12 months ago       1.84kB
[root@ubuntu1804 ~]#ll -h nginx.tar.gz 
-rw------- 1 root root 125M Jan 25 20:44 nginx.tar.gz
[root@ubuntu1804 ~]#tar xvf nginx.tar.gz  -C /data
09d204271b2674da08db25af2990d9dbc2dfb64bffd97368e36fbf11fa133234/
09d204271b2674da08db25af2990d9dbc2dfb64bffd97368e36fbf11fa133234/VERSION
09d204271b2674da08db25af2990d9dbc2dfb64bffd97368e36fbf11fa133234/json
09d204271b2674da08db25af2990d9dbc2dfb64bffd97368e36fbf11fa133234/layer.tar
5ad3bd0e67a9c542210a21a3c72f56ef6387cf9b7f4c2506d2398d55a2593ed0.json
bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc/
bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc/VERSION
bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc/json
bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc/layer.tar
c485148312456ba8bca62ab3ff47d4c43944edf5a2618340816c2db26902668b/
c485148312456ba8bca62ab3ff47d4c43944edf5a2618340816c2db26902668b/VERSION
c485148312456ba8bca62ab3ff47d4c43944edf5a2618340816c2db26902668b/json
c485148312456ba8bca62ab3ff47d4c43944edf5a2618340816c2db26902668b/layer.tar
manifest.json
repositories
[root@ubuntu1804 ~]#ll /data
total 36
drwxr-xr-x  5 root root 4096 Jan 25 20:45 ./
drwxr-xr-x 24 root root 4096 Dec 12  2018 ../
drwxr-xr-x  2 root root 4096 Jan 22 12:26 09d204271b2674da08db25af2990d9dbc2dfb64bffd97368e36fbf11fa133234/
-rw-r--r--  1 root root 6669 Jan 22 12:26 5ad3bd0e67a9c542210a21a3c72f56ef6387cf9b7f4c2506d2398d55a2593ed0.json
drwxr-xr-x  2 root root 4096 Jan 22 12:26 bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc/
drwxr-xr-x  2 root root 4096 Jan 22 12:26 c485148312456ba8bca62ab3ff47d4c43944edf5a2618340816c2db26902668b/
-rw-r--r--  1 root root  355 Jan  1  1970 manifest.json
-rw-r--r--  1 root root   88 Jan  1  1970 repositories
[root@ubuntu1804 ~]#cat /data/manifest.json 
[{"Config":"5ad3bd0e67a9c542210a21a3c72f56ef6387cf9b7f4c2506d2398d55a2593ed0.json","RepoTags":["nginx:latest"],"Layers":["bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc/layer.tar","c485148312456ba8bca62ab3ff47d4c43944edf5a2618340816c2db26902668b/layer.tar","09d204271b2674da08db25af2990d9dbc2dfb64bffd97368e36fbf11fa133234/layer.tar"]}]
[root@ubuntu1804 ~]#cd /data/bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc/
[root@ubuntu1804 bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc]#ls
json  layer.tar  VERSION
[root@ubuntu1804 bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc]#tar xf layer.tar 
[root@ubuntu1804 bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc]#ls
bin  boot  dev  etc  home  json  layer.tar  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var  VERSION
[root@ubuntu1804 ~]#cat /data/bc0c1f0bf5d3d116df7db18438f547181e0695612a45744f7964713c1126cebc/etc/issue
Debian GNU/Linux 10 \n \l

[root@ubuntu1804 ~]#docker image  history centos:centos7.7.1908
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
08d05d1d5859        2 months ago        /bin/sh -c #(nop)  CMD ["/bin/bash"]            0B                  
<missing>           2 months ago        /bin/sh -c #(nop)  LABEL org.label-schema.sc…   0B                  
<missing>           2 months ago        /bin/sh -c #(nop) ADD file:3e2a127b44ed01afc…   204MB
搜索镜像
搜索镜像

可以官方网站进行镜像的搜索 http://hub.docker.com

docker-镜像管理插图(3)
docker-镜像管理插图(4)

在官方的docker 仓库中搜索指定名称的docker镜像,也会有很多三方镜像。

可以执行docker search命令进行搜索

格式如下:

Usage:  docker search [OPTIONS] TERM
说明:
OFFICIAL:官方
AUTOMATED:使用第三方docker服务来帮助编译镜像,可以在互联网上面直接拉取到镜像,减少了繁琐的编译过程

范例:

[root@ubuntu1804 ~]#docker search centos
NAME                               DESCRIPTION                                     STARS               OFFICIAL            AUTOMATED
centos                             The official build of CentOS.                   5786                [OK]                
ansible/centos7-ansible            Ansible on Centos7                              126                                     [OK]
jdeathe/centos-ssh                 OpenSSH / Supervisor / EPEL/IUS/SCL Repos - …   114                                     [OK]
consol/centos-xfce-vnc             Centos container with "headless" VNC session…   108                                     [OK]
centos/mysql-57-centos7            MySQL 5.7 SQL database server                   67                                      
imagine10255/centos6-lnmp-php56    centos6-lnmp-php56                              57                                      [OK]
tutum/centos                       Simple CentOS docker image with SSH access      44                                      
centos/postgresql-96-centos7       PostgreSQL is an advanced Object-Relational …   40                                      
centos/httpd-24-centos7            Platform for running Apache httpd 2.4 or bui…   29                                      
kinogmt/centos-ssh                 CentOS with SSH                                 29                                      [OK]
pivotaldata/centos-gpdb-dev        CentOS image for GPDB development. Tag names…   10                                      
drecom/centos-ruby                 centos ruby                                     6                                       [OK]
centos/tools                       Docker image that has systems administration…   5                                       [OK]
mamohr/centos-java                 Oracle Java 8 Docker image based on Centos 7    3                                       [OK]
darksheer/centos                   Base Centos Image -- Updated hourly             3                                       [OK]
pivotaldata/centos                 Base centos, freshened up a little with a Do…   3                                       
pivotaldata/centos-mingw           Using the mingw toolchain to cross-compile t…   2                                       
miko2u/centos6                     CentOS6 日本??境                                   2                                       [OK]
pivotaldata/centos-gcc-toolchain   CentOS with a toolchain, but unaffiliated wi…   2                                       
indigo/centos-maven                Vanilla CentOS 7 with Oracle Java Developmen…   1                                       [OK]
mcnaughton/centos-base             centos base image                               1                                       [OK]
blacklabelops/centos               CentOS Base Image! Built and Updates Daily!     1                                       [OK]
pivotaldata/centos6.8-dev          CentosOS 6.8 image for GPDB development         0                                       
pivotaldata/centos7-dev            CentosOS 7 image for GPDB development           0                                       
smartentry/centos                  centos with smartentry                          0                                       [OK]
[root@ubuntu1804 ~]#

范例:选择性的查找镜像

[root@ubuntu1804 ~]#docker search -s 30  centos
Flag --stars has been deprecated, use --filter=stars=3 instead
NAME                              DESCRIPTION                                     STARS               OFFICIAL            AUTOMATED
centos                            The official build of CentOS.                   5836                [OK]                
ansible/centos7-ansible           Ansible on Centos7                              128                                     [OK]
jdeathe/centos-ssh                OpenSSH / Supervisor / EPEL/IUS/SCL Repos - …   114                                     [OK]
consol/centos-xfce-vnc            Centos container with "headless" VNC session…   109                                     [OK]
centos/mysql-57-centos7           MySQL 5.7 SQL database server                   69                                      
imagine10255/centos6-lnmp-php56   centos6-lnmp-php56                              58                                      [OK]
tutum/centos                      Simple CentOS docker image with SSH access      45                                      
centos/postgresql-96-centos7      PostgreSQL is an advanced Object-Relational …   40   

#新语法
[root@ubuntu1804 ~]#docker  search --filter=stars=30 centos
NAME                              DESCRIPTION                                     STARS               OFFICIAL            AUTOMATED
centos                            The official build of CentOS.                   5831                [OK]                
ansible/centos7-ansible           Ansible on Centos7                              128                                     [OK]
jdeathe/centos-ssh                OpenSSH / Supervisor / EPEL/IUS/SCL Repos - …   114                                     [OK]
consol/centos-xfce-vnc            Centos container with "headless" VNC session…   109                                     [OK]
centos/mysql-57-centos7           MySQL 5.7 SQL database server                   69                                      
imagine10255/centos6-lnmp-php56   centos6-lnmp-php56                              58                                      [OK]
tutum/centos                      Simple CentOS docker image with SSH access      45                                      
centos/postgresql-96-centos7      PostgreSQL is an advanced Object-Relational …   40   

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Docker-服务进程管理

docker-anpine镜像介绍

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