KVM服务器启动时systemd-networkd报Permission denied导致网络无法启动，手动执行netplan命令可恢复的问题排查求助

大家好，我最近在我的KVM服务器上做了些改动：安装了几台虚拟机，还搭建了一台DNS服务器。结果现在服务器启动时出现了状况——网络没法正常启动，同时弹出了不少报错信息：

blkmapd[726]: open pipe file /run/rpc_pipefs/nfs/blocklayout failed: No such file or directory

systemd-networkd[732]: Failed to connect to bus: Permission denied
systemd-networkd[732]: Could not connect to bus: Permission denied

kernel: iwlwifi 0000:00:14.3 wlo1: renamed from wlan0

systemd[1]: systemd-networkd.service: Main process exited, code=exited, status=1/FAILURE
systemd[1]: systemd-networkd.service: Failed with result 'exit-code'.
systemd[1]: Failed to start Network Configuration.
systemd[1]: Dependency failed for Wait for Network to be Configured.
systemd[1]: systemd-networkd-wait-online.service: Job systemd-networkd-wait-online.service/start failed with result 'dependency'.
systemd[1]: systemd-timesyncd.service: Scheduled restart job, restart counter is at 1.
systemd[1]: systemd-networkd.service: Scheduled restart job, restart counter is at 1.

启动完成后网络始终处于断开状态，cloud-init检测到的设备信息如下：

cloud-init[754]: ci-info: ++++++++++++++++++++++++++++Net device info++++++++++++++++++++++++++++
cloud-init[754]: ci-info: +---------+-------+-----------+-----------+-------+-------------------+
cloud-init[754]: ci-info: |  Device |   Up  |  Address  |    Mask   | Scope |     Hw-Address    |
cloud-init[754]: ci-info: +---------+-------+-----------+-----------+-------+-------------------+
cloud-init[754]: ci-info: | enp89s0 | False |     .     |     .     |   .   | 88:ae:dd:04:0e:1e |
cloud-init[754]: ci-info: |    lo   |  True | 127.0.0.1 | 255.0.0.0 |  host |         .         |
cloud-init[754]: ci-info: |    lo   |  True |  ::1/128  |     .     |  host |         .         |
cloud-init[754]: ci-info: |   wlo1  | False |     .     |     .     |   .   | bc:09:1b:83:95:ff |
cloud-init[754]: ci-info: +---------+-------+-----------+-----------+-------+-------------------+

不过我直接登录服务器执行sudo netplan try，再跟着执行sudo netplan apply之后，网络就又能正常工作了，执行这两个命令时的系统日志如下：

Aug 09 09:00:08 atlas systemd-networkd[1993]: br0: Re-configuring with /run/systemd/network/10-netplan-br0.network
Aug 09 09:00:08 atlas systemd-networkd[1993]: br0: DHCPv6 lease lost
Aug 09 09:00:08 atlas systemd-networkd[1993]: enp89s0: Re-configuring with /run/systemd/network/10-netplan-enp89s0.network
Aug 09 09:00:08 atlas systemd-networkd[1993]: enp89s0: Re-configuring with /run/systemd/network/10-netplan-enp89s0.network
Aug 09 09:00:08 atlas systemd-networkd[1993]: br0: Re-configuring with /run/systemd/network/10-netplan-br0.network
Aug 09 09:00:08 atlas systemd-networkd[1993]: br0: DHCPv6 lease lost
Aug 09 09:00:08 atlas systemd[1]: Condition check resulted in OpenVSwitch configuration for cleanup being skipped.
Aug 09 09:00:08 atlas sudo[2040]: pam_unix(sudo:session): session closed for user root
Aug 09 09:00:08 atlas systemd[1]: Reloading Postfix Mail Transport Agent (instance -)...

我的netplan配置文件/etc/netplan/00-installer-config.yaml内容如下：

# This is the network config written by 'subiquity'
#network:
#  ethernets:
#    enp89s0:
#      dhcp4: true
#  version: 2

network:
version: 2
renderer: networkd
ethernets:
enp89s0:
dhcp4: false
dhcp6: false
#addresses: [192.168.1.239/24]
#gateway4: 192.168.1.1
#mtu: 1500
#nameservers:
#  addresses: [8.8.8.8]
bridges:
br0:
interfaces: [enp89s0]
addresses: [192.168.0.15/24]
gateway4: 192.168.0.1
mtu: 1500
nameservers:
addresses: [127.0.0.1, 192.168.0.1, 8.8.8.8]
parameters:
stp: true
forward-delay: 4
dhcp4: no
dhcp6: no

有没有大佬能指点一下，我应该从哪些方面入手排查这个问题呢？

备注：内容来源于stack exchange，提问作者Josef