How to build your own ubuntu image with docker?
一. Build a ubuntu image and install sshd
1. Pull ubuntu
docker pull ubuntu:14.042. Create Dockerfile
FROM ubuntu:14.04
#update
RUN apt-get update
#install gcc
RUN apt-get install -y gcc
#install vim
RUN apt-get install -y vim
#install sshd
RUN apt-get install -y openssh-server
RUN mkdir /var/run/sshd
#create user
RUN useradd admin
RUN echo 'admin:admin' |chpasswd
#start sshd
EXPOSE 22
CMD ["/usr/sbin/sshd", "-D"]3. Build image
docker build -t ubuntu-sshd-admin .
Build then check image.
$ docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-sshd-admin latest 82a9040e58aa 14 minutes ago 380MB4. Run
docker run -d -p 222:22 ubuntu-sshd-admin
docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d87645ff3fa2 ubuntu-sshd-admin "/usr/sbin/sshd -D" 7 minutes ago Up 7 minutes 0.0.0.0:222->22/tcp unruffled_mirzakhani5. Client test
ssh admin@127.0.0.1 -p 222
Use admin:admin to login, then you will find sshd is already started.
$ ps -elf | grep sshd
4 S root 1 0 0 80 0 - 15346 - 04:05 ? 00:00:00 /usr/sbin/sshd -D
4 S root 22 1 0 80 0 - 23138 - 04:13 ? 00:00:00 sshd: admin [priv]
5 S admin 33 22 0 80 0 - 23138 - 04:13 ? 00:00:00 sshd: admin@pts/0
0 S admin 37 34 0 80 0 - 2219 - 04:14 pts/0 00:00:00 grep sshd
$二. Install more software
1. Create new Dockerfile
If you require additional software within your system, you may opt to create more Dockerfiles and construct updated versions of the image.
For example, if you want to install vim, you can write a new Dockerfile.vim
FROM ubuntu-sshd-admin
#install vim
RUN apt-get install -y vimAnd now we have two dockerfiles.
2. Build a new version
docker build -t ubuntu-sshd-admin:0.1 . -f Dockerfile.vim
By running This command, we can install a new version of ubuntu-ssh-admin, and this allows us to verify.
$ docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-sshd-admin 0.1 dbea46204d20 8 minutes ago 414MB
ubuntu-sshd-admin latest 82a9040e58aa 3 hours ago 380MBWe can try rebooting the container to observe whether vim is installed on your Ubuntu system.
docker run -d -p 222:22 ubuntu-sshd-admin:0.1
三. Create a volume for ubuntu
1. create a volume
wangyachangdeMacBook-Pro:docker wangyachang$ docker volume create ubuntu
ubuntu
wangyachangdeMacBook-Pro:docker wangyachang$ docker volume inspect ubuntu
[
{
"CreatedAt": "2018-06-21T07:31:06Z",
"Driver": "local",
"Labels": {},
"Mountpoint": "/var/lib/docker/volumes/ubuntu/_data",
"Name": "ubuntu",
"Options": {},
"Scope": "local"
}
]2. start ubuntu
Then we can initiate the Ubuntu image by assigning it to the volume previously created.
wangyachangdeMacBook-Pro:ubuntu wangyachang$ docker run -d -p 222:22 --mount type=volume,source=ubuntu,target=/world ubuntu-sshd-admin:0.2
da637a55cb71589f58397a446f00bd5703e7d219e6f12250062c7b13d1dbba48We can can creat a file in the /world directory.
root@1c67af3a9a6e:/# touch /world/data.txt
root@1c67af3a9a6e:/# ls /world/data.txt
/world/data.txt由于作者将docker安装在mac上，并将其配置为运行于虚拟机环境中，并考虑到mac系统的docker服务被设置为只能在虚拟机内运行的特点，在这种情况下访问该指定目录会导致无法找到的问题
/var/lib/docker/volumes/ubuntu/_data/Applications/Docker.app/Contents/MacOS/com.docker.driver.amd64-linux
四. 挂载一个主机目录作为数据卷
通过 -v 标识符同样可以配置将本地已有的目录挂载到容器中作为存储卷：
启动容器并在指定端口上运行映射本地端口到容器中将文件夹 /Users/wangyachang/Documents/docker/ubuntu/ubuntu_data 挂载到 /world_data Ubuntu SSH代理服务版本号为ubuntu-sshd-admin 的版本号为0.1版（截至发布前）
通过指定的命令操作，本机位于ubuntu_data目录的文件将被成功连接至容器内的world_data目录，并完成整个数据同步流程。
参考文献：
. https://yeasy.gitbooks.io/docker_practice/introduction/
五. 保存容器到镜像
基于已有的docker容器，做一新的dokcer image.
$ docker commit <container_id> <image_name>
如何看启动容器日志：
$ sudo docker logs -f -t 容器名
六. FAQ
在mac系统中使用Docker存储镜像的位置位于$/Users/wangyachang/Library/Containers/com.docker...中