Ubuntu配置DNS解析

国内国外都有很多的厂商提供了免费的公共DNS，比如：

DNSPod Public DNS：119.29.29.29 阿里云公共DNS：223.5.5.5/223.6.6.6 Google Public DNS：8.8.8.8/8.8.4.4

系统通过读取/etc/resolv.conf中的DNS地址进行查询，默认DNS服务器IP是127.0.0.53

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 127.0.0.53

该文件是一个软链接，其指向/run/systemd/resolve/resolv.conf

如何设置公共DNS

• 第一步：调整/etc/resolv.conf的软链接，使其指向文件/run/systemd/resolve/resolv.conf

  $ cd /etc
  $ sudo ln -sf /run/systemd/resolve/resolv.conf 
  

• 第二步：修改配置文件/etc/systemd/resolved.conf，添加新的DNS服务器IP

  $ cat /etc/systemd/resolved.conf
  #  This file is part of systemd.
  #
  #  systemd is free software; you can redistribute it and/or modify it
  #  under the terms of the GNU Lesser General Public License as published by
  #  the Free Software Foundation; either version 2.1 of the License, or
  #  (at your option) any later version.
  #
  # Entries in this file show the compile time defaults.
  # You can change settings by editing this file.
  # Defaults can be restored by simply deleting this file.
  #
  # See resolved.conf(5) for details
  
  [Resolve]
  DNS=1.1.1.1 192.168.1.1 119.29.29.29
  #FallbackDNS=
  #Domains=
  #LLMNR=no
  #MulticastDNS=no
  #DNSSEC=no
  #Cache=yes
  #DNSStubListener=yes
  

• 第三步：重启系统服务

  sudo service systemd-resolved restart
  

完成后，可以查看新的/etc/resolv.conf配置