Tschösi's questions

有一段时间，我一直无法启动 ModemManager 服务。

➜  ~ systemctl status ModemManager.service
× ModemManager.service - Modem Manager
     Loaded: loaded (/lib/systemd/system/ModemManager.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Fri 2022-09-30 19:39:32 CEST; 21s ago
    Process: 23668 ExecStart=/usr/sbin/ModemManager (code=exited, status=127)
   Main PID: 23668 (code=exited, status=127)
        CPU: 26ms

Sep 30 19:39:32 tsch systemd[1]: Starting Modem Manager...
Sep 30 19:39:32 tsch systemd[1]: ModemManager.service: Main process exited, code=exited, status=127/n/a
Sep 30 19:39:32 tsch systemd[1]: ModemManager.service: Failed with result 'exit-code'.
Sep 30 19:39:32 tsch systemd[1]: Failed to start Modem Manager.

但是，手动启动 ModemManager 可以正常工作：

➜  ~ sudo ModemManager
ModemManager[25946]: <info>  ModemManager (version 1.16.6) starting in system bus...
...

服务文件 ( /etc/systemd/system/dbus-org.freedesktop.ModemManager1.service) 如下所示：

[Unit]
Description=Modem Manager
After=polkit.service
Requires=polkit.service

[Service]
Type=dbus
BusName=org.freedesktop.ModemManager1
ExecStart=/usr/sbin/ModemManager
StandardError=null
Restart=on-abort
CapabilityBoundingSet=CAP_SYS_ADMIN CAP_NET_ADMIN
ProtectSystem=true
ProtectHome=true
PrivateTmp=true
RestrictAddressFamilies=AF_NETLINK AF_UNIX AF_QIPCRTR
NoNewPrivileges=true
User=root

[Install]
WantedBy=multi-user.target
Alias=dbus-org.freedesktop.ModemManager1.service

关于这里有什么问题的任何想法？在 Ubuntu 22.04 上运行

编辑：在我输入这个问题的过程中，它显然已自行修复，现在它按预期工作。我仍然对为什么会发生这种情况感兴趣:)

我的设置如下：

我在 address 有一个本地 DNS 服务器（准确地说是 pihole）192.168.1.200。我的家庭网络中的 address 也有一台服务器192.168.1.300。我的域example.com指向我的公共 IP 5.5.5.5。pihole 有一些自定义的 DNS 条目，因此当我在本地网络中时，example.com解析为192.168.1.300而不是5.5.5.5（以避免 NAT 出现问题）我已将我的 wifi 的 DNS 服务器设置为192.168.1.200. （也是在路由器里设置的……）

现在不知何故，我仍然从 systemd-resolve 获得 5.5.5.5 IP。

我已经用 sudo systemd-resolve --flush-caches

sudo systemd-resolve --statistics返回缓存大小为 0

systemd-resolve --status | grep "DNS Servers"节目192.168.1.200

现在是有趣的部分：

dig example.com返回5.5.5.5

而 dig example.com @192.168.1.200返回192.168.1.300

这怎么可能？如何让 systemd-resolve 实际查询我设置的 DNS 服务器？

更多信息：

• ls -al /etc/resolv.conf返回 lrwxrwxrwx 1 root root 39 Sep 26 2019 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf
• cat /etc/resolv.conf返回

# 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
search home

• dpkg -l *dnsmasq*返回

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                   Version          Architecture     Description
+++-======================-================-================-==================================================
un  dnsmasq                <none>           <none>           (no description available)
ii  dnsmasq-base           2.79-1           amd64            Small caching DNS proxy and DHCP/TFTP server
un  dnsmasq-base-lua       <none>           <none>           (no description available)

• grep -i dns /etc/systemd/resolved.conf返回

#DNS=
#FallbackDNS=
#MulticastDNS=no
#DNSSEC=no
#DNSStubListener=yes