在国内想要下载镜像比较困难，因此很多公司都构建自己的私有仓库。如何搭建私有仓库，请参考《docker私有仓库从无到有》。然而即使私有仓库服务构建完成，但是里面没有镜像，一样很苦恼。今天介绍一下如何利用国内云服务商提供的镜像加速器，来快速下载镜像。
目前国内docker镜像加速器服务商，质量比较好的有阿里云、DaoCloud以及Docker中国。
它们配置都是相同，获取专属加速地址，然后将地址写到docker配置文件/etc/docker/daemon.json中。
一、阿里云加速地址：
1、注册阿里云账号，如果有淘宝号也是可以的。https://dev.aliyun.com/search.html
2、注册并登陆成功之后，进入之后点击管理中心
3、进入管理中心，默认业务就是下图，然后在选择镜像加速器，里面就是专属加速地址，并且有配置方法。
DaoCloud配置方式与阿里云类似，只是服务商不一样罢了。
二、 Docker 中国如果不想注册阿里云，那么可以使用Docker中国提供的服务。
可以将https://registry.docker-cn.com，设置到registry-mirrors中即可（与阿里云设置方式一样）。具体方法，可参考https://www.docker-cn.com/registry-mirror。
以上设置好镜像之后，不需要docker login进行登录。
三、遇到问题
问题1：设置完加速地址之后，输入如下命令：
[root@localhost docker]# docker pull mysql
Using default tag: latest
Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
[root@localhost docker]#
[root@localhost docker]# 查看具体日志信息：
[root@localhost docker]# grep docker /var/log/messages
Mar 7 15:59:06 localhost dockerd: time="2018-03-07T15:59:06.551882623+08:00" level=warning msg="Error getting v2 registry: Get https://6jwksk60.mirror.aliyuncs.com/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"
Mar 7 15:59:06 localhost dockerd: time="2018-03-07T15:59:06.551997545+08:00" level=error msg="Not continuing with pull after error: Get https://6jwksk60.mirror.aliyuncs.com/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"
Mar 7 15:59:06 localhost dockerd: time="2018-03-07T15:59:06.552080576+08:00" level=error msg="Handler for POST /v1.35/images/create returned error: Get https://6jwksk60.mirror.aliyuncs.com/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"
Mar 7 15:59:08 localhost dockerd: time="2018-03-07T15:59:08.441427015+08:00" level=debug msg="Calling GET /_ping"
Mar 7 15:59:08 localhost dockerd: time="2018-03-07T15:59:08.449887376+08:00" level=debug msg="Calling GET /v1.35/info"
Mar 7 15:59:08 localhost dockerd: time="2018-03-07T15:59:08.485088164+08:00" level=debug msg="Calling POST /v1.35/images/create?fromImage=mysql&tag=latest"
Mar 7 15:59:08 localhost dockerd: time="2018-03-07T15:59:08.547151332+08:00" level=debug msg="hostDir: /etc/docker/certs.d/6jwksk60.mirror.aliyuncs.com"
Mar 7 15:59:08 localhost dockerd: time="2018-03-07T15:59:08.547231472+08:00" level=debug msg="Trying to pull mysql from https://6jwksk60.mirror.aliyuncs.com/ v2"
Mar 7 15:59:23 localhost dockerd: time="2018-03-07T15:59:23.548000137+08:00" level=warning msg="Error getting v2 registry: Get https://6jwksk60.mirror.aliyuncs.com/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"
Mar 7 15:59:23 localhost dockerd: time="2018-03-07T15:59:23.548084051+08:00" level=info msg="Attempting next endpoint for pull after error: Get https://6jwksk60.mirror.aliyuncs.com/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"
Mar 7 15:59:23 localhost dockerd: time="2018-03-07T15:59:23.548133902+08:00" level=debug msg="Trying to pull mysql from https://registry-1.docker.io v2"
Mar 7 15:59:38 localhost dockerd: time="2018-03-07T15:59:38.548628804+08:00" level=warning msg="Error getting v2 registry: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"
Mar 7 15:59:38 localhost dockerd: time="2018-03-07T15:59:38.548715275+08:00" level=info msg="Attempting next endpoint for pull after error: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"
Mar 7 15:59:38 localhost dockerd: time="2018-03-07T15:59:38.548798878+08:00" level=error msg="Handler for POST /v1.35/images/create returned error: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"实际错误是：
Get https://6jwksk60.mirror.aliyuncs.com/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)"
【定位过程】通过curl进行验证：curlhttps://6jwksk60.mirror.aliyuncs.com/v2/_catalog 是可以正常返回结果，说明服务没有问题
通过谷歌翻墙（百度不行，解决不了这个问题），一共大概有两种方式
1、设置dns，在/etc/resolv.conf，以及/etc/docker/daemon.json中增加dns。例如dns地址：8.8.8.8
2、设置docker代理（centos和ubuntu同样设置）
[root@localhost docker]# mkdir -p /etc/systemd/system/docker.service.d
[root@localhost docker]# cat > /etc/systemd/system/docker.service.d/http-proxy.conf <<EOF
> [Service]
> Environment="HTTP_PROXY=http://proxy.example.com:80/" "HTTPS_PROXY=https://proxy.example.com:443/"
> EOF
[root@localhost docker]#然后重启服务
[root@localhost docker]# systemctl daemon-reload
[root@localhost docker]# systemctl restart docker查看配置
[root@localhost docker]# systemctl show --property=Environment docker
Environment=HTTP_PROXY=http://proxy.example.com:80/ HTTPS_PROXY=https://proxy.example.com:443/
[root@localhost docker]# 设置完成后再进行docker pull就可以下载了。
【分析一下原因】
1、通过curl来判断服务是正常的，所以肯定是docker配置问题。
2、当前环境在公司内网，公司是有代理的，因此可以肯定是公司网络问题，通过谷歌搜索，最终确定需要为docker指定代理。