远程ssh登录Linux缓慢
查看secure日志，发现大量如下标志性记录：
Oct 26 21:23:26 localhost crond[31374]: pam_systemd(crond:session): Failed to create session: Activation of org.freedesktop.login1 timed out
Oct 26 21:24:26 localhost crond[31515]: pam_systemd(crond:session): Failed to create session: Connection timed out
什么是 org.freedesktop.login1
那么，org.freedesktop.login1 是个什么玩意呢？参见 org.freedesktop.login1 官方文档。
org.freedesktop.login1 — The D-Bus interface of systemd-logind
systemd-logind.service(8) 是跟踪用户登录和"座位"的系统服务。
守护进程提供了C库接口和D-Bus接口。C库接口用于反省和监控用户登录和"座位"的状态。D-Bus接口除了提供相同的功能外，还能更改系统状态。更多内容参见 sd-login(3)。
Activation of org.freedesktop.login1 timed out 怎么处理
查看bus状态，关注org.freedesktop.login1和org.freedesktop.systemd1
[root@core log]# busctl --list
NAME PID PROCESS USER CONNECTION UNIT SESSION DESCRIPTION
:1.0 1 systemd root :1.0 - - -
:1.136950 12472 polkitd polkitd :1.136950 polkit.service - -
:1.157995 18442 busctl root :1.157995 sshd.service - -
fi.epitest.hostap.WPASupplicant - - - (activatable) - -
fi.w1.wpa_supplicant1 - - - (activatable) - -
org.freedesktop.DBus - - - - - - -
org.freedesktop.NetworkManager - - - (activatable) - -
org.freedesktop.PolicyKit1 12472 polkitd polkitd :1.136950 polkit.service - -
org.freedesktop.hostname1 - - - (activatable) - -
org.freedesktop.locale1 - - - (activatable) - -
org.freedesktop.login1 - - - (activatable) - -
org.freedesktop.machine1 - - - (activatable) - -
org.freedesktop.nm_dispatcher - - - (activatable) - -
org.freedesktop.systemd1 1 systemd root :1.0 - - -
org.freedesktop.timedate1 - - - (activatable) - -
再查看一台正常的服务器，发现org.freedesktop.login1的状态是不一样的。如下：
[root@hadoop ~]# busctl --list
NAME PID PROCESS USER CONNECTION UNIT SESSION DESCRIPTION
:1.0 1 systemd root :1.0 - - -
:1.1 843 polkitd polkitd :1.1 polkit.service - -
:1.18 1060 tuned root :1.18 tuned.service - -
:1.2 853 systemd-logind root :1.2 systemd-logind.service - -
:1.3 852 NetworkManager root :1.3 NetworkManager.service - -
:1.400 26323 busctl root :1.400 session-179.scope 179 -
:1.7 852 NetworkManager root :1.7 NetworkManager.service - -
com.redhat.ifcfgrh1 852 NetworkManager root :1.7 NetworkManager.service - -
com.redhat.tuned 1060 tuned root :1.18 tuned.service - -
fi.epitest.hostap.WPASupplicant - - - (activatable) - -
fi.w1.wpa_supplicant1 - - - (activatable) - -
org.freedesktop.DBus 844 dbus-daemon dbus org.freedesktop.DBus dbus.service - -
org.freedesktop.NetworkManager 852 NetworkManager root :1.3 NetworkManager.service - -
org.freedesktop.PolicyKit1 843 polkitd polkitd :1.1 polkit.service - -
org.freedesktop.hostname1 - - - (activatable) - -
org.freedesktop.import1 - - - (activatable) - -
org.freedesktop.locale1 - - - (activatable) - -
org.freedesktop.login1 853 systemd-logind root :1.2 systemd-logind.service - -
org.freedesktop.machine1 - - - (activatable) - -
org.freedesktop.nm_dispatcher - - - (activatable) - -
org.freedesktop.systemd1 1 systemd root :1.0 - - -
org.freedesktop.timedate1 - - - (activatable) - -
[root@hadoop ~]#
那么查看D-Bus日志，大量类似如下的重复报错：
[root@core log]# journalctl -u dbus
...
Oct 29 12:49:01 core dbus[10830]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Oct 29 12:49:01 core dbus-daemon[10830]: dbus[10830]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Oct 29 12:49:26 core dbus[10830]: [system] Failed to activate service 'org.freedesktop.login1': timed out
Oct 29 12:49:26 core dbus-daemon[10830]: dbus[10830]: [system] Failed to activate service 'org.freedesktop.login1': timed out
[root@core log]# systemctl status dbus
● dbus.service - D-Bus System Message Bus
Loaded: loaded (/usr/lib/systemd/system/dbus.service; static; vendor preset: disabled)
Active: active (running) since Mon 2020-07-20 21:14:01 CST; 3 months 9 days ago
Main PID: 10830 (dbus-daemon)
CGroup: /system.slice/dbus.service
└─10830 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
Oct 29 12:50:01 core dbus[10830]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Oct 29 12:50:01 core dbus-daemon[10830]: dbus[10830]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Oct 29 12:50:26 core dbus[10830]: [system] Failed to activate service 'org.freedesktop.login1': timed out
Oct 29 12:50:26 core dbus-daemon[10830]: dbus[10830]: [system] Failed to activate service 'org.freedesktop.login1': timed out
Oct 29 12:51:01 core dbus[10830]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Oct 29 12:51:01 core dbus-daemon[10830]: dbus[10830]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Oct 29 12:51:26 core dbus[10830]: [system] Failed to activate service 'org.freedesktop.login1': timed out
Oct 29 12:51:26 core dbus-daemon[10830]: dbus[10830]: [system] Failed to activate service 'org.freedesktop.login1': timed out
Oct 29 12:52:01 core dbus[10830]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
Oct 29 12:52:01 core dbus-daemon[10830]: dbus[10830]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service'
既然org.freedesktop.login1是systemd-logind的D-Bus接口，那么我们重启 systemd-logind
[root@core log]# systemctl restart systemd-logind
使用journalctl -f -u dbus查看日志，没有再出现报错。再次使用ssh远程连接，恢复正常了。
参考文档
https://www.freedesktop.org/software/systemd/man/org.freedesktop.login1.html
https://support.oracle.com/knowledge/Oracle%20Linux%20and%20Virtualization/2614155_1.html