Ubuntu 22.04 LTS重启后需手动启动systemd-resolved才能正常上网的问题求助

昨天一切都还正常，但今天（重启后）我突然无法访问互联网了。奇怪的是，我能ping通8.8.8.8，但无法解析google.com，显然是DNS解析出了问题。

当我执行以下命令后，网络就恢复正常了：

sudo systemctl enable systemd-resolved

我查看了systemd-resolved的状态，输出如下：

systemd-resolved.service - Network Name Resolution

Loaded: loaded (/lib/systemd/system/systemd-resolved.service; disabled; vendor preset: enabled)

Active: active (running) since Tue 2023-07-18 21:07:34 CEST; 40min ago

Docs: man:systemd-resolved.service(8)

man:org.freedesktop.resolve1(5)

https://www.freedesktop.org/wiki/Software/systemd/writing-network-configuration-managers

https://www.freedesktop.org/wiki/Software/systemd/writing-resolver-clients

Main PID: 12966 (systemd-resolve)

Status: "Processing requests..."

Tasks: 1 (limit: 9213)

Memory: 4.9M

CPU: 1.073s

CGroup: /system.slice/systemd-resolved.service

└─12966 /lib/systemd/systemd-resolved

jul 18 21:07:34 chewbacca systemd-resolved[12966]: Positive Trust Anchors:

jul 18 21:07:34 chewbacca systemd-resolved[12966]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc683457104237c7f8ec8d

jul 18 21:07:34 chewbacca systemd-resolved[12966]: Negative trust anchors: home.arpa 10.in-addr.arpa 16.172.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.a>

jul 18 21:07:34 chewbacca systemd-resolved[12966]: Using system hostname 'chewbacca'.

jul 18 21:07:34 chewbacca systemd-resolved[12966]: wlp2s0: Bus client set default route setting: yes

jul 18 21:07:34 chewbacca systemd[1]: Started Network Name Resolution.

jul 18 21:07:34 chewbacca systemd-resolved[12966]: wlp2s0: Bus client set DNS server list to: 46.227.67.134, 192.165.9.158

jul 18 21:07:48 chewbacca systemd-resolved[12966]: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server 46.227.67.134.

jul 18 21:13:02 chewbacca systemd-resolved[12966]: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server 46.227.67.134.

jul 18 21:15:39 chewbacca systemd-resolved[12966]: Grace period over, resuming full feature set (UDP+EDNS0) for DNS server 46.227.67.134.

另外，我已经在/etc/systemd/resolved.conf里配置了DNS服务器，文件内容如下：

#  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. Local configuration
# should be created by either modifying this file, or by creating "drop-ins" in
# the resolved.conf.d/ subdirectory. The latter is generally recommended.
# Defaults can be restored by simply deleting this file and all drop-ins.
#
# Use 'systemd-analyze cat-config systemd/resolved.conf' to display the full config.
#
# See resolved.conf(5) for details.

[Resolve]
# Some examples of DNS servers which may be used for DNS= and FallbackDNS=:
# 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
# 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
# Quad9:      9.9.9.9#dns.quad9.net 149.112.112.112#dns.quad9.net 2620:fe::fe#dns.quad9.net 2620:fe::9#dns.quad9.net
DNS=46.227.67.134
FallbackDNS=192.165.9.158
#Domains=
#DNSSEC=no
#DNSOverTLS=no
#MulticastDNS=no
#LLMNR=no
#Cache=no-negative
#CacheFromLocalhost=no
#DNSStubListener=yes
#DNSStubListenerExtra=
#ReadEtcHosts=yes
#ResolveUnicastSingleLabel=no

我已经做了这些操作：

• 在路由器里设置了相同的两个DNS服务器
• 通过GUI在网络连接的IPv4设置选项卡中添加了这两个DNS服务器

但现在还是每次重启后都需要手动启动systemd-resolved才能正常上网，我已经谷歌搜索了好几个小时都没找到原因，实在有点摸不着头绪，希望各位能给我一些指点！

谢谢！

备注：内容来源于stack exchange，提问作者Evert Homan