docker学习(4) DevOps视角

纵观Docker

• 运维(Ops)视角

• 开发(Dev)视角

• 运维包括：下载镜像、运行新的容器，在容器内运行命令、以及销毁容器

• 开发包括：与应用相关的内容，比如从github拉取一些应用，解释其中的Dockerfile，将应用容器化，在容器里运行他们。

• 快速启动Docker的方式：Play With Docker：http：//play-with-docker.com/

运维视角

• 安装Docker涉及两个组将：Docker客户端和Docker daemon
• daemon实现了Docker引擎的API
• Linux默认安装的视角，客户端和daemon之间的通信是通过本地IPC/UNIX Socker完成的(/var/run/docker.sock)
• 使用docker version命令来检查客户端和服务端是否已经成功运行，并且可以相互通信。

$ docker version
Client: Docker Engine - Community
 Version:           19.03.4
 API version:       1.40
 Go version:        go1.12.10
 Git commit:        9013bf583a
 Built:             Fri Oct 18 15:53:51 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.4
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.10
  Git commit:       9013bf583a
  Built:            Fri Oct 18 15:52:23 2019
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.2.10
  GitCommit:        b34a5c8af56e510852c35414db4c1f4fa6172339
 runc:
  Version:          1.0.0-rc8+dev
  GitCommit:        3e425f80a8c931f88e6d94a8c831b9d5aa481657
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683

镜像

• 可以将Docker镜像理解为一个包含OS文件系统和应用的对象。
• 在Docker世界里，镜像实际上等价于未启动的容器。
• 查看镜像

~$ docker image ls 
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE

• 获取一个新镜像——ubuntu:latest

$ docker pull ubuntu:latest
latest: Pulling from library/ubuntu
22e816666fd6: Pull complete 
079b6d2a1e53: Pull complete 
11048ebae908: Pull complete 
c58094023a2e: Pull complete 
Digest: sha256:a7b8b7b33e44b123d7f997bd4d3d0a59fafc63e203d17efedf09ff3f6f516152
Status: Downloaded newer image for ubuntu:latest
docker.io/library/ubuntu:latest
lhf@lhf-virtual-machine:~$ docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
ubuntu              latest              cf0f3ca922e0        4 days ago          64.2MB

• Docker每个镜像都有自己的唯一ID
• 用户可以通过镜像的ID和名称来使用镜像

容器

• 启动容器

$ docker container run -it ubuntu:latest /bin/bash
root@19e6da84f9c4:/# ls
bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

• docker container run命令使Docker daemon启动新的容器

• -it 参数将Shell切换到容器终端，开启容器的交互模式，使当前的shell连接到容器的终端

• 使用ps查看容器的进程

root@19e6da84f9c4:/# ps -elf
F S UID         PID   PPID  C PRI  NI ADDR SZ WCHAN  STIME TTY          TIME CMD
4 S root          1      0  0  80   0 -  4627 wait   14:38 pts/0    00:00:00 /bin/bash
4 R root         11      1  0  80   0 -  8600 -      14:56 pts/0    00:00:00 ps -elf

• 按Ctrl-PQ组合键，可以退出容器的同时来保持容器的运行。
• 查看系统内全部运行状态的容器

$ docker container ls
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
19e6da84f9c4        ubuntu:latest       "/bin/bash"         22 minutes ago      Up 22 minutes                           unruffled_hoover

连接到运行中的容器

• 连接到运行中的容器

$ docker container exec -it unruffled_hoover bash
root@19e6da84f9c4:/# ls
bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

• 使用命令docker container stop 和docker container rm来停止并杀死容器

$ docker container stop unruffled_hoover
unruffled_hoover
lhf@lhf-virtual-machine:~$ docker container ls
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
docker container ls -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                      PORTS               NAMES
19e6da84f9c4        ubuntu:latest       "/bin/bash"         28 minutes ago      Exited (0) 44 seconds ago                       unruffled_hoover
lhf@lhf-virtual-machine:~$ docker container rm unruffled_hoover
unruffled_hoover
lhf@lhf-virtual-machine:~$ docker container ls -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

• -a 的参数让Docker列出所有容器，包括已经停止的状态的容器。

开发视角

• 容器及应用
• 分析一份应用代码的Dockefile并容器化，最终以容器的方式运行。

$ ll psweb-master/
总用量 36
drwxrwxr-x 4 lhf lhf 4096 10月 23 23:11 ./
drwxrwxr-x 6 lhf lhf 4096 10月 23 23:11 ../
-rw-rw-r-- 1 lhf lhf  341 10月 23 23:11 app.js
-rw-rw-r-- 1 lhf lhf  216 10月 23 23:11 circle.yml
-rw-rw-r-- 1 lhf lhf  338 10月 23 23:11 Dockerfile
-rw-rw-r-- 1 lhf lhf  421 10月 23 23:11 package.json
-rw-rw-r-- 1 lhf lhf  370 10月 23 23:11 README.md
drwxrwxr-x 2 lhf lhf 4096 10月 23 23:11 test/
drwxrwxr-x 2 lhf lhf 4096 10月 23 23:11 views/

• 查看dockerfile内容

$ cat Dockerfile 
# Test web-app to use with Pluralsight courses and Docker Deep Dive book
# Linux x64
FROM alpine

LABEL maintainer="nigelpoulton@hotmail.com"

# Install Node and NPM
RUN apk add --update nodejs nodejs-npm

# Copy app to /src
COPY . /src

WORKDIR /src

# Install dependencies
RUN  npm install

EXPOSE 8080

ENTRYPOINT ["node", "./app.js"]

• 根据Dockerfile中的指令来创建新的容器

$ docker  build -t test:latest .
Sending build context to Docker daemon  10.24kB
Step 1/8 : FROM alpine
latest: Pulling from library/alpine
89d9c30c1d48: Pull complete 
Digest: sha256:c19173c5ada610a5989151111163d28a67368362762534d8a8121ce95cf2bd5a
Status: Downloaded newer image for alpine:latest
 ---> 965ea09ff2eb
Step 2/8 : LABEL maintainer="nigelpoulton@hotmail.com"
 ---> Running in 75106e6bad84
Removing intermediate container 75106e6bad84
 ---> 5935d67da60e
Step 3/8 : RUN apk add --update nodejs nodejs-npm
 ---> Running in 56b0d36a8f41
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/community/x86_64/APKINDEX.tar.gz
(1/8) Installing ca-certificates (20190108-r0)
(2/8) Installing c-ares (1.15.0-r0)
(3/8) Installing libgcc (8.3.0-r0)
(4/8) Installing http-parser (2.9.2-r0)
(5/8) Installing libstdc++ (8.3.0-r0)
(6/8) Installing libuv (1.29.1-r0)
(7/8) Installing nodejs (10.16.3-r0)
(8/8) Installing npm (10.16.3-r0)
Executing busybox-1.30.1-r2.trigger
Executing ca-certificates-20190108-r0.trigger
OK: 59 MiB in 22 packages
Removing intermediate container 56b0d36a8f41
 ---> dc254500dcda
Step 4/8 : COPY . /src
 ---> 6c293be80bd1
Step 5/8 : WORKDIR /src
 ---> Running in ebc1257e0d2c
Removing intermediate container ebc1257e0d2c
 ---> 4f515774097f
Step 6/8 : RUN  npm install
 ---> Running in 48bb066e51b2
npm WARN deprecated superagent@3.8.3: Please note that v5.0.1+ of superagent removes User-Agent header by default, therefore you may need to add it yourself (e.g. GitHub blocks requests without a User-Agent header).  This notice will go away with v5.0.2+ once it is released.
npm WARN deprecated json3@3.3.2: Please use the native JSON object instead of JSON 3

> core-js@2.6.10 postinstall /src/node_modules/core-js
> node postinstall || echo "ignore"

Thank you for using core-js ( https://github.com/zloirock/core-js ) for polyfilling JavaScript standard library!

The project needs your help! Please consider supporting of core-js on Open Collective or Patreon: 
> https://opencollective.com/core-js 
> https://www.patreon.com/zloirock 

Also, the author of core-js ( https://github.com/zloirock ) is looking for a good job -)

npm notice created a lockfile as package-lock.json. You should commit this file.
added 163 packages from 460 contributors and audited 262 packages in 29.419s
found 5 vulnerabilities (2 low, 2 moderate, 1 critical)
  run `npm audit fix` to fix them, or `npm audit` for details
Removing intermediate container 48bb066e51b2
 ---> 677c10bc6201
Step 7/8 : EXPOSE 8080
 ---> Running in 2ab783cd6ca3
Removing intermediate container 2ab783cd6ca3
 ---> a3656648909c
Step 8/8 : ENTRYPOINT ["node", "./app.js"]
 ---> Running in 7495a0f5807a
Removing intermediate container 7495a0f5807a
 ---> e63fd667d16a
Successfully built e63fd667d16a
Successfully tagged test:latest

• 查看当前镜像

$ docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED              SIZE
test                latest              e63fd667d16a        About a minute ago   71.4MB
alpine              latest              965ea09ff2eb        46 hours ago         5.55MB
ubuntu              latest              cf0f3ca922e0        4 days ago           64.2MB

• 从镜像启动容器，并测试应用

$ docker container run -d --name web1 --publish 8080:8080 test:latest
6906f6b41b395cf0e35a1dad541beb827830e8584124ae2e8c723bfc97262570

• 登录网页查看测试

6.png

• 将应用代码构建到Dockerfile——docker镜像当中，已容器的方式启动镜像，这个过程叫做“应用容器化”