本文为随笔简记，记述 /etc/systemd/system.conf 修改后生效方法
方法有二
- 重启主机
- 执行
systemctl daemon-reexec
使用daemon-reload无效原因
单纯使用 systemctl daemon-reload 是不会对/etc/systemd/system.conf刷新的，引用下serverfault.com对systemd-system.conf的说明
No, daemon-reload will reload all unit files, not the configuration for systemd itself. However, # systemctl daemon-reexec will re-execute systemd and cause it to digest its new configuration in the process.
From the systemctl man page:
daemon-reexec
Reexecute the systemd manager. This will serialize the manager
state, reexecute the process and deserialize the state again. This
command is of little use except for debugging and package upgrades.
Sometimes, it might be helpful as a heavy-weight daemon-reload.
While the daemon is being reexecuted, all sockets systemd listening
on behalf of user configuration will stay accessible.
When the man page says daemon-reexec is useful for package upgrades, it in large part means that this command executes whatever new binaries there are and re-processes its configs. HOWEVER, the RPM that we use to upgrade systemd already contains a script to do this, so it is usually never needed in the case of a normal upgrade.
Or you can reboot. Either will do.
也就是说，daemon-reexec 会重新执行systemd管理器，重新读取系统配置文件，而daemon-reload只会去读service部分的配置，不包含全局配置/systemd/system.conf，相当于重量级的daemon-reload.