官方介绍：http://rpm-packaging-guide.github.io/#epoch
[root@CentOs7 ～]# yum list docker --showduplicates 已加载插件：fastestmirror, priorities Loading mirror speeds from cached hostfile 28 packages excluded due to repository priority protections 可安装的软件包 docker.x86_64 2:1.12.6-55.gitc4618fb.el7.centos c7-media
看到版本号前是2:1.12.6，1.12.6是版本号，是常见的，但是2:是什么意思，google了一下，发现这个是rpm包的命名规范，即使不写也会默认为0，是指的依赖版本号
中文RPM包信息： 看到 "时期 ：2"
[root@CentOs7 ～]# yum info docker-1.12.6
已加载插件：fastestmirror, priorities
Loading mirror speeds from cached hostfile
28 packages excluded due to repository priority protections
可安装的软件包
名称 ：docker
架构 ：x86_64
时期 ：2
版本 ：1.12.6
发布 ：55.gitc4618fb.el7.centos
大小 ：15 M
源 ：c7-media_CentOS
简介 ： Automates deployment of containerized applications
网址 ：https://github.com/docker/docker
协议 ： ASL 2.0
描述 ： Docker is an open-source engine that automates the deployment of any
: application as a lightweight, portable, self-sufficient container that will
: run virtually anywhere.
:
: Docker containers can encapsulate any payload, and will run consistently on
: and between virtually any server. The same container that a developer builds
: and tests on a laptop will run at scale, in production*, on VMs, bare-metal
: servers, OpenStack clusters, public instances, or combinations of the above.
英文RPM包信息：对应的的是Epoch
[root@CentOs7 yum.repos.d]# yum info docker-1.12.6
Loaded plugins: fastestmirror, priorities
Loading mirror speeds from cached hostfile
28 packages excluded due to repository priority protections
Available Packages
Name : docker
Arch : x86_64
Epoch : 2
Version : 1.12.6
Release : 55.gitc4618fb.el7.centos
Size : 15 M
Repo : c7-media_CentOS
Summary : Automates deployment of containerized applications
URL : https://github.com/docker/docker
License : ASL 2.0
Description : Docker is an open-source engine that automates the deployment of any
: application as a lightweight, portable, self-sufficient container that will
: run virtually anywhere.
:
: Docker containers can encapsulate any payload, and will run consistently on
: and between virtually any server. The same container that a developer builds
: and tests on a laptop will run at scale, in production*, on VMs, bare-metal
: servers, OpenStack clusters, public instances, or combinations of the above.
参考：
http://unix.stackexchange.com/questions/543384/what-is-the-meaning-of-1-in-the-version-of-a-yum-package