为什么同一网络中的两个 Ubuntu 系统在 DNS 解析中表现不同？

编辑（tl；博士）

我似乎在这里确定了部分问题，因为至少/etc/resolv.conf和相关文件的差异已经消失。

但我仍然无法通过 WiFi 连接，因此其他差异可能仍然存在。

我的意思是识别这些，并采取行动。

我故意选择了与此 OP相同的标题。我有两个 Ubuntu 系统，server1并且server2在各方面都非常相似。两者都通过 WiFi 连接到同一个路由器。我通过比较两个系统来帮助跟踪问题。

在server2，我刚开始遇到 DNS 名称解析问题。我已连接到 VPN，并且服务器已重新启动，所以我猜这个 PostScriptum可能会描述这种情况。 server2没有resolvconf，我安装了它作为结果。当时/etc/resolv.conf开始指向/run/resolvconf/resolv.conf（注意下面的修改日期），而不是/run/systemd/resolve/stub-resolv.conf. 为此，我必须在顶部手动添加/etc/resolv.conf名称服务器 8.8.8.8 ，插入有线互联网连接，我可以立即sudo apt update等。注意：截至目前，上面链接中引用的文件权限问题不存在. 如果下次我连接/断开 VPN 时出现，我会处理它。

我在下面列出：1)和中的不同之处server1，server22)两者中的相同之处（any替换服务器名称），以及 3)几乎相同的地方（据我了解，有不相关的差异）。

为什么DIFFERENCE #3在下面？( nameserver ::1)。 如果可能，
如何通过保留与 ? 相同的配置来修复? server2server1 我可以尝试修改/etc/resolvconf/resolv.conf.d/tailin server2，但由于该文件在server1此操作中为空，因此即使成功，也可能会掩盖其他问题。

我想如果我只能修复下面的 DIFFERENCES #1-4，那将解决问题。但是所有 4 个文件都被引用为动态创建的。我找不到谁负责/负责“创造”差异，以及如何解决这个问题。

不同的

dig：

[server1]$ dig google.com

; <<>> DiG 9.16.1-Ubuntu <<>> google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 64202
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;google.com.            IN  A

;; ANSWER SECTION:
google.com.     94  IN  A   216.58.202.46

;; Query time: 36 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: mar ago 10 03:44:51 -03 2021
;; MSG SIZE  rcvd: 55

对比

[server2]$ dig google.com

; <<>> DiG 9.16.1-Ubuntu <<>> google.com
;; global options: +cmd
;; connection timed out; no servers could be reached

/etc/resolv.conf及相关文件：

[server1]$ cat /etc/resolv.conf 
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 127.0.0.53
search fibertel.com.ar                                     <--- DIFFERENCE #1

[server1]$ cat /run/systemd/resolve/stub-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 "resolvectl 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 trust-ad
search fibertel.com.ar                                     <--- DIFFERENCE #2

[server1]$ cat /run/systemd/resolve/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 directly to
# all known uplink DNS servers. This file lists all configured search domains.
#
# 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 192.168.0.1                                     <--- DIFFERENCE #3
search fibertel.com.ar                                     <--- DIFFERENCE #3

[server1]$ cat /run/resolvconf/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 127.0.0.53
search fibertel.com.ar                                     <--- DIFFERENCE #4

[server1]$ ll /etc/resolv.conf 
lrwxrwxrwx 1 root root 29 feb  1  2021 /etc/resolv.conf -> ../run/resolvconf/resolv.conf
[server1]$ ll /run/resolvconf/resolv.conf
-rw-r--r-- 1 root root 327 ago  9 20:59 /run/resolvconf/resolv.conf

对比

[server2]$ cat /etc/resolv.conf 
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 127.0.0.53

[server2]$ cat /run/systemd/resolve/stub-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 "resolvectl 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 trust-ad

[server2]$ cat /run/systemd/resolve/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 directly to
# all known uplink DNS servers. This file lists all configured search domains.
#
# 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 ::1                                     <--- DIFFERENCE #3

[server2]$ cat /run/resolvconf/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 127.0.0.53

[server2]$ ll /etc/resolv.conf
lrwxrwxrwx 1 root root 29 ago  9 22:38 /etc/resolv.conf -> ../run/resolvconf/resolv.conf
[server2]$ ll /run/resolvconf/resolv.conf
-rw-r--r-- 1 root root 304 ago 10 03:13 /run/resolvconf/resolv.conf

相同的

[any]$ uname -a
Linux <serverN> 5.11.0-25-generic #27~20.04.1-Ubuntu SMP Tue Jul 13 17:41:23 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

[any]$ dpkg -l | grep resolvconf
ii  resolvconf                                    1.82                                all          name server information handler

[any]$ cat /etc/netplan/01-network-manager-all.yaml 
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager

[any]$ cat /etc/NetworkManager/NetworkManager.conf
[main]
plugins=ifupdown,keyfile

[ifupdown]
managed=false

[device]
wifi.scan-rand-mac-address=no

[any]$ cat /etc/hosts
127.0.0.1   localhost
127.0.1.1   <serverN>

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

[any]$ cat /etc/nsswitch.conf
...
[any]$ cat /etc/systemd/networkd.conf 
...
[any]$ ss -plnt | grep ':53'
LISTEN   0        4096       127.0.0.53%lo:53            0.0.0.0:* 
[any]$ sudo systemctl status resolvconf.service
...
[any]$ /lib/systemd/network/
...

差不多一样

[server1]$ lsb_release -a
LSB Version:    core-11.1.0ubuntu2-noarch:security-11.1.0ubuntu2-noarch
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.2 LTS
Release:    20.04
Codename:   focal

[server2]$ lsb_release -a
LSB Version:    core-11.1.0ubuntu2-noarch:printing-11.1.0ubuntu2-noarch:security-11.1.0ubuntu2-noarch
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.2 LTS
Release:    20.04
Codename:   focal

相关：

1. DNS 设置为 systemd 的 127.0.0.53 - 如何永久更改？