ubuntu解决域名不能访问的问题

刚装好的ubuntu22.04或ubuntu20.04不能访问百度，然后发现只能ping通ip，而不能ping通www.baidu.com，网上查了下解决方案，

• 方案一：修改dns：
  修改 /etc/resolv.conf配置文件，但很快就会被覆盖，文件第二行已经声明Do not edit.

  # 显示如下
  # This is /run/systemd/resolve/stub-resolv.conf managed by man:systemd-resolved(8).
  # Do not edit.
  #
  # This file might be symlinked as /etc/resolv.conf. If you're looking at
  # /etc/resolv.conf and seeing this text, you have followed the symlink.
  #
  # This is a dynamic resolv.conf file for connecting local clients to the
  # internal DNS stub resolver of systemd-resolved. This file lists all
  # configured search domains.
  #
  # Run "resolvectl status" to see details about the uplink DNS servers
  # currently in use.
  #
  # Third party programs should typically not access this file directly, but only
  # through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
  # different way, replace this symlink by a static file or a different symlink.
  #
  # See man:systemd-resolved.service(8) for details about the supported modes of
  # operation for /etc/resolv.conf.
  
  # nameserver 127.0.0.53
  nameserver 8.8.8.8
  nameserver 114.114.114.114
  options edns0 trust-ad
  search .
  

  将nameserver改为8.8.8.8后保存，再次ping www.baidu.com恢复正常，不出意外的话很快就会发现/etc/resolve.conf又回去了，只好再次寻找查找解决办法

• 方案二：
  修改/etc/systemd/resolved.conf，去除DNS前的#，修改值如下：

  #  This file is part of systemd.
    2 #
    3 #  systemd is free software; you can redistribute it and/or modify it under the
    4 #  terms of the GNU Lesser General Public License as published by the Free
    5 #  Software Foundation; either version 2.1 of the License, or (at your option)
    6 #  any later version.
    7 #
    8 # Entries in this file show the compile time defaults. Local configuration
    9 # should be created by either modifying this file, or by creating "drop-ins" in
   10 # the resolved.conf.d/ subdirectory. The latter is generally recommended.
   11 # Defaults can be restored by simply deleting this file and all drop-ins.
   12 #
   13 # Use 'systemd-analyze cat-config systemd/resolved.conf' to display the full config.
   14 #
   15 # See resolved.conf(5) for details.
   16 
   17 [Resolve]
   18 # Some examples of DNS servers which may be used for DNS= and FallbackDNS=:
   19 # Cloudflare: 1.1.1.1#cloudflare-dns.com 1.0.0.1#cloudflare-dns.com 2606:4700:4700::    1111#cloudflare-dns.com 2606:4700:4700::1001#cloudflare-dns.com
   20 # Google:     8.8.8.8#dns.google 8.8.4.4#dns.google 2001:4860:4860::8888#dns.google     2001:4860:4860::8844#dns.google
   21 # Quad9:      9.9.9.9#dns.quad9.net 149.112.112.112#dns.quad9.net 2620:fe::fe#dns.qu    ad9.net 2620:fe::9#dns.quad9.net
   22 DNS=8.8.8.8 114.114.114.114
   23 #FallbackDNS=
   24 #Domains=
   25 #DNSSEC=no
   26 #DNSOverTLS=no
   27 #MulticastDNS=no
   28 #LLMNR=no
   29 #Cache=no-negative
   30 #CacheFromLocalhost=no
   31 #DNSStubListener=yes
   32 #DNSStubListenerExtra=
   33 #ReadEtcHosts=yes
   34 #ResolveUnicastSingleLabel=no
  
  

  重启域名解析服务

  systemctl restart systemd-resolved
  systemctl enable systemd-resolved
  

  备份当前的/etc/resolve.conf，并重新设置/run/systemd/resolve/resolv.conf 到/etc/resolve.conf的软链接

  mv /etc/resolv.conf /etc/resolv.conf.bak
  ln -s /run/systemd/resolve/resolv.conf /etc/
  

• 大功告成