前言：
上篇文章讲了docker的几个基本概念，这篇文章讲怎么在Linux下安装Docker的过程。
正文：
有yum命令和脚本安装两种方式，这里主要讲yum安装的方式
一、安装前准备
1.系统要求
Docker CE支持64位版本CenOS7,并且要求内核版本不低于3.10
查看内核版本的指令
[root@localhost 桌面]# uname -r
3.10.0-327.el7.x86_642.如果原系统里安装着旧版本，先卸载旧版本。旧版本的Docker称为docker或者docker-engine,使用以下命令卸载旧版本：
[root@localhost 桌面]# sudo yum remove docker二、安装
1.安装的指令
[root@localhost 桌面]# yum install docker-ce
如果出现下面的提示：没有可用软件包，这个时候需要安装必要的软件依赖及更新增加docker-ce yum源
已加载插件：fastestmirror, langpacks
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
base | 3.6 kB 00:00
extras | 3.4 kB 00:00
updates | 3.4 kB 00:00
(1/4): extras/7/x86_64/primary_db | 205 kB 00:00
(2/4): base/7/x86_64/group_gz | 166 kB 00:00
(3/4): base/7/x86_64/primary_db | 6.0 MB 00:01
(4/4): updates/7/x86_64/primary_db | 6.5 MB 00:01
Loading mirror speeds from cached hostfile
* base: mirrors.huaweicloud.com
* extras: mirrors.huaweicloud.com
* updates: mirrors.huaweicloud.com
没有可用软件包 docker-ce。
错误：无须任何处理安装docker-ce yum源的指令有两步:
[root@localhost 桌面]# sudo yum install -y yum-utils device-mapper-persistent-data lvm2rpm.x86_64 0:4.11.3-35.el7
rpm-build-libs.x86_64 0:4.11.3-35.el7
rpm-libs.x86_64 0:4.11.3-35.el7
rpm-python.x86_64 0:4.11.3-35.el7
yum.noarch 0:3.4.3-161.el7.centos
完毕！sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker.ce.repo此处可能会报错 （原因是国内访问不到docker官方镜像的缘故），解决办法就是换成阿里云的地址
[root@localhost 桌面]# $sudo yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo出现下面的提示内容就表示成功
已加载插件：fastestmirror, langpacks
adding repo from: http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
grabbing file http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo to /etc/yum.repos.d/docker-ce.repo
repo saved to /etc/yum.repos.d/docker-ce.repo
2.再次执行yum install docker-ce 指令就不会报错啦，连输入两次Y，出现完毕就docker安装成功
事务概要
=================================================================================
安装 1 软件包 (+ 3 依赖软件包)
升级 ( 14 依赖软件包)
总计：69 M
总下载量：69 M
Is this ok [y/d/N]: y
总计 7.5 MB/s | 69 MB 00:09
从 https://mirrors.aliyun.com/docker-ce/linux/centos/gpg 检索密钥
导入 GPG key 0x621E9F35:
用户ID : "Docker Release (CE rpm) <[email protected]>"
指纹 : 060a 61c5 1b55 8a7f 742b 77aa c52f eb6b 621e 9f35
来自 : https://mirrors.aliyun.com/docker-ce/linux/centos/gpg
是否继续？[y/N]：y
作为依赖被升级:
libseccomp.x86_64 0:2.3.1-3.el7
libselinux.x86_64 0:2.5-14.1.el7
libselinux-devel.x86_64 0:2.5-14.1.el7
libselinux-python.x86_64 0:2.5-14.1.el7
libselinux-utils.x86_64 0:2.5-14.1.el7
libsemanage.x86_64 0:2.5-14.el7
libsemanage-python.x86_64 0:2.5-14.el7
libsepol.x86_64 0:2.5-10.el7
libsepol-devel.x86_64 0:2.5-10.el7
policycoreutils.x86_64 0:2.5-29.el7_6.1
policycoreutils-python.x86_64 0:2.5-29.el7_6.1
selinux-policy.noarch 0:3.13.1-229.el7_6.12
selinux-policy-targeted.noarch 0:3.13.1-229.el7_6.12
setools-libs.x86_64 0:3.3.8-4.el7
完毕！
3.启动docker的指令和开启启动
[root@localhost 桌面]# systemctl start docker[root@localhost 桌面]# systemctl enable docker4.查看docker的安装信息
[root@localhost 桌面]# docker infoContainers: 0
Running: 0
Paused: 0
Stopped: 0
Images: 0
Server Version: 18.09.7
Storage Driver: devicemapper
Pool Name: docker-253:0-941162-pool
Pool Blocksize: 65.54kB
Base Device Size: 10.74GB
Backing Filesystem: xfs
Udev Sync Supported: true
Data file: /dev/loop0
Metadata file: /dev/loop1
Data loop file: /var/lib/docker/devicemapper/devicemapper/data
Metadata loop file: /var/lib/docker/devicemapper/devicemapper/metadata
Data Space Used: 11.8MB
Data Space Total: 107.4GB
Data Space Available: 11.66GB
Metadata Space Used: 581.6kB
Metadata Space Total: 2.147GB
Metadata Space Available: 2.147GB
Thin Pool Minimum Free Space: 10.74GB
Deferred Removal Enabled: true
Deferred Deletion Enabled: true
Deferred Deleted Device Count: 0
Library Version: 1.02.149-RHEL7 (2018-07-20)
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 894b81a4b802e4eb2a91d1ce216b8817763c29fb
runc version: 425e105d5a03fabd737a126ad93d62a9eeede87f
init version: fec3683
Security Options:
seccomp
Profile: default
Kernel Version: 3.10.0-327.el7.x86_64
Operating System: CentOS Linux 7 (Core)
OSType: linux
Architecture: x86_64
CPUs: 1
Total Memory: 1.782GiB
Name: localhost.localdomain
ID: 5DKJ:SW65:PU6Q:MHYY:NNXQ:RPOL:KWBB:GGG5:M7C6:XUFU:MGUF:EMWA
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false
Product License: Community Engine5.测试docker是否安装正确
docker run hello-world #启动一个基于hello-world镜像的容器若输出以下信息，则说明安装成功
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete
Digest: sha256:6540fc08ee6e6b7b63468dc3317e3303aae178cb8a45ed3123180328bcc1d20f
Status: Downloaded newer image for hello-world:latest
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. 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/总结：
docker的安装起来还是比较简单的，但是在理解上可能需要下点功夫。
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