systemd

背景

见之前centOS ssh登录缓慢解决
深挖了下原因总结成本文。

systemd-logind简介：

Namesystemd-logind.service, systemd-logind — Login managerSynopsissystemd-logind.service/usr/lib/systemd/systemd-logindDescriptionsystemd-logind is a system service that manages user logins. It is responsible for:Keeping track of users and sessions, their processes and their idle state. This is implemented by allocating a systemd slice unit for each user below user.slice, and a scope unit below it for each concurrent session of a user. Also, a per-user service manager is started as system service instance of user@.service for each user logged in.Generating and managing session IDs. If auditing is available and an audit session ID is set for a session already, the session ID is initialized from it. Otherwise, an independent session counter is used.Providing PolicyKit-based access for users to operations such as system shutdown or sleepImplementing a shutdown/sleep inhibition logic for applicationsHandling of power/sleep hardware keysMulti-seat managementSession switch managementDevice access management for usersAutomatic spawning of text logins (gettys) on virtual console activation and user runtime directory management

问题

发现在执行机上systemd-logind导致cpu 100%的问题，使得登录异常缓慢，并且消耗资源。

原因

1. systemd-logind主要功能是为每一个登陆session创建一个systemd角度的cgroup管理对象，更方便对session使用cgroup，在实际场景中没有什么用处，关闭不会影响正常ssh登陆
2. 在有crond任务时，触发systemd-logind回收不及时的bug

解决办法

关闭systemd-logind

systemctl stop systemd-logind

验证是否已经修复方法：
如果systemd-logind 状态如下所示，已经将systemd-logind关闭

systemctl status systemd-logind