过了一段时间，Ubuntu不再从DNS-Server找到主机

Question

由于几天，我有一个Raspberry Pi与dnsmasq设置为DNS服务器192.168.1.2在我的局域网。它可以帮助其他计算机根据名字找到服务器..。它工作得很好，除了我的Ubuntu18.04笔记本电脑，它似乎不知何故“忘了”服务器。

当笔记本电脑启动时，一开始一切正常。在命令行nslookup server.lan中，主机server.lan，ping server.lan都给出了正确的结果，并且在服务器上打开一个网页很好。

xeros@laptop:~ $ nslookup server.lan
Server:     127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
Name:   server.lan
Address: 192.168.1.3

然而，过了一段时间，它就停止工作了。从服务器打开网站时说找不到它，nslookup突然失败：

xeros@laptop:~ $ nslookup server.lan
Server:     127.0.0.53
Address:    127.0.0.53#53

** server can't find server.lan: NXDOMAIN

不过，DNS-服务器正在工作。我的智能手机或其他设备没有问题。另外，如果我指定DNS-Server，正确的答案将在我的Ubuntu膝上型计算机上返回：

xeros@laptop:~ $ nslookup server.lan 192.168.1.2
Server:     192.168.1.2
Address:    192.168.1.2#53

Non-authoritative answer:
Name:   server.lan
Address: 192.168.1.3

如果我重启笔记本电脑，一切都会好起来的。

我不知道为什么过了一段时间就失败了。有人知道会出什么问题吗？

根据请求编辑其他信息(在RPi DNS-服务器上执行)：

pi@raspberry:~ $ ls -al /etc/resolv.conf
-rw-r--r-- 1 root root 47 Dec  8 16:43 /etc/resolv.conf

pi@raspberry:~ $ cat /etc/resolv.conf
# Generated by resolvconf
nameserver 127.0.0.1

pi@raspberry:~ $ 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=
#FallbackDNS=8.8.8.8 8.8.4.4 2001:4860:4860::8888 2001:4860:4860::8844
#Domains=
#LLMNR=yes
#DNSSEC=no
#Cache=yes
#DNSStubListener=udp

笔记本电脑也是如此：

xeros@laptop:~$ ls -al /etc/resolv.conf
lrwxrwxrwx 1 root root 39 Mai  1  2018 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf

xeros@laptop:~$ cat /etc/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# 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 "systemd-resolve --status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs must 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
options edns0

xeros@laptop:~$ 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=
#FallbackDNS=
#Domains=
#LLMNR=no
#MulticastDNS=no
#DNSSEC=no
#Cache=yes
#DNSStubListener=yes

Answer 1

在Ubuntu笔记本上试试这个..。这是我在AU上的另一个答案.

报告回来..。

我们需要检查您的DNS服务器(dnsmasq)在/etc/解析式中的options edns0是否有问题。

goes是一个指向三个位置之一的符号链接。做a：

ls -al /etc/resolv.conf #注意原始的符号链接设置

sudo cat /etc/resolv.conf #注意当前的文件内容

sudo rm -i /etc/resolv.conf #删除符号链接

sudo ln -s /run/resolvconf/resolv.conf /etc/resolv.conf #新符号链接

sudo cat /etc/resolv.conf #注意当前的文件内容

使用以下方法重新测试DNS：

host -v www.booking.com | grep -i received #每次使用不同的网站

sudo rm -i /etc/resolv.conf #删除符号链接

根据结果，还可以尝试以下符号链接：

sudo ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf #一个不同的符号链接

sudo cat /etc/resolv.conf #注意当前的文件内容

使用以下方法重新测试DNS：

host -v www.booking.com | grep -i received #每次使用不同的网站

sudo rm -i /etc/resolv.conf #删除符号链接

如果一个符号链接比另一个更好，那么暂时保持它。如果没有更好的方法，请将其设置为原来的：

sudo ln -s /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf #重置为原始符号链接