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Ubuntu 一段时间后不再从 DNS 服务器找到主机

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Ubuntu 一段时间后不再从 DNS 服务器找到主机

几天以来，我在 LAN 中将 dnsmasq 设置为 192.168.1.2 上的 DNS 服务器的 Raspberry Pi 设置为 DNS 服务器。它可以帮助其他计算机通过名称找到服务器...并且运行良好，但我的 Ubuntu 18.04 笔记本电脑除外，它似乎不知何故“忘记”了服务器。

笔记本电脑启动后，一开始一切正常。从命令行 nslookup server.lan、host server.lan、ping server.lan 均给出正确结果，并且服务器上的网页打开正常。

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

但过了一会儿它就停止工作了。从服务器打开网站时提示无法找到，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

DNS 服务器正在运行。我的智能手机或任何其他设备上都没有问题。此外，如果我指定 DNS 服务器，我的 Ubuntu 笔记本电脑上会返回正确的答案：

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

如果我重新启动笔记本电脑，一切又可以正常工作。

我不知道为什么过了一段时间后它就失败了。有人知道可能出了什么问题吗？

根据要求编辑了其他信息（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

笔记本电脑也一样：

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

答案1

在 Ubuntu 笔记本电脑上尝试一下...这是我在 AU 上的另一个答案中剪辑的...

报告...

我们需要检查您的 DNS 服务器（dnsmasq）的 /etc/resolv.conf 是否存在问题options edns0。

/etc/resolv.conf 是一个符号链接，指向以下三个位置之一。请执行以下操作：

ls -al /etc/resolv.conf# 注意原始符号链接设置

sudo cat /etc/resolv.conf# 记下当前文件内容

sudo rm -i /etc/resolv.conf# 删除符号链接

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

sudo cat /etc/resolv.conf# 记下当前文件内容

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​​，您还可以尝试此符号链接：

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

sudo cat /etc/resolv.conf# 记下当前文件内容

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，请暂时保留它。如果没有更好的效果，请将其设置回原始状态：

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

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