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docker build运行apt-get update失败¶

进入ubuntu:18.04容器，运行apt-get update失败

$ docker run -it ubuntu:18.04
root@06f6c91954e1:/# apt-get update
Err:1 http://security.ubuntu.com/ubuntu bionic-security InRelease        
  Temporary failure resolving 'security.ubuntu.com'
Err:2 http://archive.ubuntu.com/ubuntu bionic InRelease                  
  Temporary failure resolving 'archive.ubuntu.com'
Err:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Err:4 http://archive.ubuntu.com/ubuntu bionic-backports InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Reading package lists... Done        
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-backports/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease  Temporary failure resolving 'security.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.
root@06f6c91954e1:/#

发现问题¶

测试是否是DNS解析出错，测试命令如下：

$ docker run busybox nslookup baidu.com
nslookup: write to '127.0.1.1': Connection refused
;; connection timed out; no servers could be reached

启动镜像busybox，使用nslookup搜索baidu.com对应IP，发现没有找到DNS服务器

解决¶

参考SOLVED: Docker build “Could not resolve ‘archive.ubuntu.com’” apt-get fails to install anything，默认Docker使用8.8.8.8作为DNS服务器地址，而不是主机的DNS服务器地址

搜索主机的DNS服务器：

$ nmcli dev show | grep 'IP4.DNS'
IP4.DNS[1]:                             192.168.0.1

临时解决方式：参数配置

$ docker run --dns 192.168.0.1 busybox nslookup www.baidu.com
Server:     192.168.0.1
Address:    192.168.0.1:53

Non-authoritative answer:
www.baidu.com   canonical name = www.a.shifen.com
Name:   www.a.shifen.com
Address: 112.80.248.76
Name:   www.a.shifen.com
Address: 112.80.248.75

*** Can't find www.baidu.com: No answer

永久解决方式：配置Docker守护进程

修改配置文件/etc/docker/daemon.json，添加主机DNS服务器后重启Docker守护进程

{
    "dns": ["192.168.0.1", "8.8.8.8", "8.8.4.4"]
}

后面两个地址是google提供的DNS服务器地址

$ systemctl restart docker

$ docker run busybox nslookup baidu.com
Server:     192.168.0.1
Address:    192.168.0.1:53

Non-authoritative answer:
Name:   baidu.com
Address: 220.181.38.148
Name:   baidu.com
Address: 39.156.69.79

*** Can't find baidu.com: No answer