1021 docker初识

docker与虚拟机相比，没有虚拟化内核，转而使用宿主机的内核。因此docker更轻更快



docker缺点：后端兼容性测试需求。把软件安装在不同的操作系统上进行测试，观察软件运行是否良好。

不能用docker做兼容性测试

uname -a 查看系统内核版本

docker关键技术：

• Namespace：通过名称控件达到了网络隔离
• 联合文件系统：通过联合文件系统达到了文件目录的隔离
• Cgroups：阻止容器中的软件和进程无限制的使用宿主机中的资源达到了资源隔离，如CPU和内存。
  
  组织容器除了内核共享，其他的都不是共享的

docker测试应用：

• 搭建测试环境
• 搭建各类基础服务
• 搭建测试执行环境

选择docker的原因：

• docker相对虚拟机轻量级，更轻更快
• docker使用简单
• docker共享，有大量的镜像可以使用

查看docker命令

Usage:	docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:
      --config string      Location of client config files (default "/Users/chenshanju/.docker")
  -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 "/Users/chenshanju/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default "/Users/chenshanju/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default "/Users/chenshanju/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Management Commands:
  builder     Manage builds
  checkpoint  Manage checkpoints
  config      Manage Docker configs
  container   Manage containers
  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
  deploy      Deploy a new stack or update an existing stack
  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.

查看docker信息

docker版本号：从17年开始，以年-月命名版本号

Containers: 3    #当前的容器
 Running: 1    #运行中的容器
 Paused: 0
 Stopped: 2    #已停止的容器
Images: 13    #镜像数量
Server Version: 18.09.0-ce-beta1    #docker版本
Storage Driver: overlay2
 Backing Filesystem: extfs
 Supports d_type: true
 Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge host ipvlan macvlan null overlay
 Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
Swarm: inactive    #容器编排
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 468a545b9edcd5932818eb9de8e72413e616e86e
runc version: 69663f0bd4b60df09991c08812a60108003fa340
init version: fec3683
Security Options:
 seccomp
  Profile: default
Kernel Version: 4.9.125-linuxkit
Operating System: Docker for Mac
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 3.855GiB
Name: linuxkit-025000000001
ID: IY7T:MW22:QBUX:KOJW:SOBV:TJUK:VXQA:HWGF:ZWXD:TAJP:KGPP:AKQ5
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): true
 File Descriptors: 32
 Goroutines: 57
 System Time: 2018-11-02T08:12:50.1509806Z
 EventsListeners: 2
HTTP Proxy: gateway.docker.internal:3128
HTTPS Proxy: gateway.docker.internal:3129
Registry: https://index.docker.io/v1/
Labels:
Experimental: true
Insecure Registries:
 127.0.0.0/8
Registry Mirrors:
 https://i2piuqyy.mirror.aliyuncs.com/
Live Restore Enabled: false
Product License: Community Engine

docker官方下载地址：https://hub.docker.com

注意：不用登陆，直接搜索镜像即可。一般选择官方镜像，如Jenkins，选择official

联合文件系统





如下载Jenkins时，有20层，Jenkins是一个经过20层文件修改生成的镜像



优点：节省硬盘空间

FAQ:

1.docker安装后，命令行使用docker，提示命令不可用，如下图所示

原因：/usr/local/bin未生效，将/usr/local/bin添加到环境变量即可

export PATH="/usr/local/bin:/usr/local/sbin:~/bin:$PATH"

2.centOS安装docker，提示Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

解决方法：

systemctl daemon-reload
sudo service docker restart
sudo service docker status
#再次执行ps，不会再报错
docker ps

sudo service docker status