执行sudo apt update时遭遇Ubuntu源域名解析临时失败问题求助

嗨，看起来你在执行sudo apt update的时候碰到了域名解析的问题，这种情况我帮很多用户排查过，大多是DNS配置或者网络连通性的小问题，咱们一步步来解决：

首先先把你遇到的错误日志贴出来方便后续参考：

root@ubuntu:/# sudo apt update

Err:1 http://archive.ubuntu.com/ubuntu focal InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Err:2 http://security.ubuntu.com/ubuntu focal-security InRelease
  Temporary failure resolving 'security.ubuntu.com'
Err:3 http://ports.ubuntu.com/ubuntu-ports focal InRelease
  Temporary failure resolving 'ports.ubuntu.com'
Err:4 http://archive.ubuntu.com/ubuntu focal-updates InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Err:5 http://ports.ubuntu.com/ubuntu-ports focal-updates InRelease
  Temporary failure resolving 'ports.ubuntu.com'
Err:6 http://archive.ubuntu.com/ubuntu focal-backports InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Err:7 http://ports.ubuntu.com/ubuntu-ports focal-backports InRelease
  Temporary failure resolving 'ports.ubuntu.com'
Err:8 http://ports.ubuntu.com/ubuntu-ports focal-security InRelease
  Temporary failure resolving 'ports.ubuntu.com'
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/focal/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/focal-updates/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/focal-backports/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/focal-security/InRelease  Temporary failure resolving 'security.ubuntu.com'
W: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal/InRelease  Temporary failure resolving 'ports.ubuntu.com'
W: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal-updates/InRelease  Temporary failure resolving 'ports.ubuntu.com'
W: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal-backports/InRelease  Temporary failure resolving 'ports.ubuntu.com'
W: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal-security/InRelease  Temporary failure resolving 'ports.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.

这个错误提示Temporary failure resolving说明你的系统没办法把Ubuntu源的域名转换成对应的IP地址，核心问题出在DNS解析上，下面是具体的排查和解决步骤：

• 第一步：先确认基础网络是否连通
  先试试ping公共DNS服务器，比如Google的8.8.8.8，看看网络本身有没有问题：

  ping -c 4 8.8.8.8
  

  如果能收到响应，说明网络是通的，问题就集中在DNS解析；如果ping不通，那得先解决网络连接问题——比如检查网线插好没、WiFi是否正常连接，或者路由器有没有故障。

• 第二步：临时更换DNS服务器测试
  如果网络没问题，那可以先临时换个靠谱的DNS服务器试试：

  1. 打开DNS配置文件：

     nano /etc/resolv.conf
     

  2. 把里面的内容替换成这两行：

     nameserver 8.8.8.8
     nameserver 8.8.4.4
     

  3. 按Ctrl+O保存，回车确认，再按Ctrl+X退出编辑器，然后重新执行sudo apt update看看能不能正常更新。

• 第三步：清理系统DNS缓存
  Ubuntu现在大多用systemd-resolved管理DNS，缓存异常也可能导致解析失败，试试清理缓存：

  sudo systemd-resolve --flush-caches
  

  然后重启DNS服务：

  sudo systemctl restart systemd-resolved
  

  完成后再跑一遍sudo apt update测试。

• 第四步：检查源列表配置是否正确
  有时候源地址拼写错误也会引发解析问题，你可以检查一下你的源配置文件：

  cat /etc/apt/sources.list
  cat /etc/apt/sources.list.d/*.list
  

  确认里面的源地址没有拼写错误，比如focal版本的源应该是http://archive.ubuntu.com/ubuntu/这类。如果发现有问题，或者想换成国内更快的镜像源，替换后再执行sudo apt update。

• 第五步：重启网络服务
  如果前面的步骤都没解决，试试重启网络服务：
  对于有线网络：

  sudo systemctl restart networking
  

  对于无线网络：

  sudo systemctl restart NetworkManager
  

  重启后再测试更新命令。

备注：内容来源于stack exchange，提问作者Chirag Pawar