docker命令总结

用 docker pull 拉取镜像

root@lishichao-virtual-machine:~# docker pull hello-world
Using default tag: latest
latest: Pulling from library/hello-world
d1725b59e92d: Pull complete
Digest: sha256:1a6fd470b9ce10849be79e99529a88371dff60c60aab424c077007f6979b4812
Status: Downloaded newer image for hello-world:latest

用 docker images 命令查看镜像的信息。

root@lishichao-virtual-machine:~# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
httpd               latest              c5a621af54e4         hours ago         178MB
hello-world         latest              4ab4c602aa5e         weeks ago         .84kB

通过 docker run 运行。      docker run --help 查看帮助

root@lishichao-virtual-machine:~# docker run hello-world

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 . The Docker client contacted the Docker daemon.
 . The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 . The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 . The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

root@lishichao-virtual-machine:~# 

-it 参数的作用是以交互模式进入容器，并打开终端。5d1eb9e31f58 是容器的内部 ID。

root@lishichao-virtual-machine:~# docker run -it centos
[root@5d1eb9e31f58 /]# 

docker ps 查看运行中的容器

root@lishichao-virtual-machine:~# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
4d85f20b58c6        centos              "/bin/bash"          seconds ago      Up  seconds                           brave_jennings

镜像命令操作

docker search 到镜像仓库搜索镜像

docker search centos

docker images 查看本地已有的镜像

[root@dns-server ~]# docker images
REPOSITORY                      TAG                 IMAGE ID            CREATED             SIZE
centos-vim-dockerfile           latest              f39351a5d35c        30 hours ago        355MB
mysql                           5.7                 1b30b36ae96a        3 days ago          372MB
mysql                           latest              ee1e8adfcefb        3 days ago          484MB
nginx                           latest              dbfc48660aeb        3 days ago          109MB

docker save 导出镜像

[root@dns-server ~]# docker save -o nginx.tar nginx
[root@dns-server ~]# ls
anaconda-ks.cfg  docker_login.sh    nginx.tar
[root@dns-server ~]# 

docker load --input 导入镜像

[root@dns-server ~]# docker load --input nginx.tar
Loaded image: nginx:latest

docker rmi 删除镜像

[root@dns-server ~]# docker rmi f39351a5d35c
Untagged: centos-vim-dockerfile:latest
Deleted: sha256:f39351a5d35ca9e00dc101c43464c3f55e9e08a240daaafc4eded43692f745fb
Deleted: sha256:f1b1df6c5b8314f3a0b3a1d5a6a96d7f20501f770b042ac1ad18b6f84164cabc

docker commit

docker commit 命令是创建新镜像最直观的方法，其过程包含三个步骤：

1. 运行容器
2. 修改容器
3. 将容器保存为新的镜像

举个例子：在 Centos base 镜像中安装 vim 并保存为新镜像。

第一步， 运行容器

root@lishichao-virtual-machine:~# docker run -it centos
[root@4d85f20b58c6 /]# 

-it 参数的作用是以交互模式进入容器，并打开终端。4d85f20b58c6 是容器的内部 ID。

第二步，安装 vim

确认vim没有安装
[root@4d85f20b58c6 /]# vim
bash: vim: command not found
安装vim
[root@4d85f20b58c6 /]# yum install vim

第三步，保存为新镜像

a.在新窗口中查看当前运行的容器。

root@lishichao-virtual-machine:~# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
4d85f20b58c6        centos              "/bin/bash"          seconds ago      Up  seconds                           brave_jennings

brave_jennings 是 Docker 为我们的容器随机分配的名字。

b. 执行 docker commit 命令将容器保存为镜像。

root@lishichao-virtual-machine:~# docker commit brave_jennings centos-with-vim
sha256:a55c595ffacac70fdd2995d898bab31dd932f6ddeeed59fdfcd52a0f695a0c82

新镜像命名为 ubuntu-with-vi。

c. 查看新镜像的属性。

root@lishichao-virtual-machine:~# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
centos-with-vim     latest              a55c595ffaca         seconds ago       355MB
httpd               latest              c5a621af54e4         hours ago         178MB
centos              latest              75835a67d134         days ago          200MB
hello-world         latest              4ab4c602aa5e         weeks ago         .84kB
ubuntu              latest              cd6d8154f1e1         weeks ago         .1MB

从 size 上看到镜像因为安装了软件而变大了。

d. 从新镜像启动容器，验证 vi 已经可以使用。

root@lishichao-virtual-machine:~# docker -it centos-with-vim
[root@c2b086c59d36 /]# which vim
/usr/bin/vim

以上演示了如何用 docker commit 创建新镜像。然而，Docker 并不建议用户通过这种方式构建镜像。原因如下：

1、这是一种手工创建镜像的方式，容易出错，效率低且可重复性弱。比如要在 debian base 镜像中也加入 vi，还得重复前面的所有步骤。

2、更重要的：使用者并不知道镜像是如何创建出来的，里面是否有恶意程序。也就是说无法对镜像进行审计，存在安全隐患。

既然 docker commit 不是推荐的方法，我们干嘛还要花时间学习呢？

原因是：即便是用 Dockerfile（推荐方法）构建镜像，底层也 docker commit 一层一层构建新镜像的。学习 docker commit 能够帮助我们更加深入地理解构建过程和镜像的分层结构。