ubuntu图形界面中无论怎么设置，系统还是会自动休眠挂机，直到碰到了如下的方法:
1.查看是否开启休眠模式
systemctl status sleep.target
发现如下所示：
● sleep.target - Sleep
Loaded: loaded (/lib/systemd/system/sleep.target; static; vendor preset: enabled)
Active: inactive (dead)
Docs: man:systemd.special(7)
2.执行关闭休眠功能的命令，如下：
sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target
可以看到系统返回：
Created symlink /etc/systemd/system/sleep.target → /dev/null.
Created symlink /etc/systemd/system/suspend.target → /dev/null.
Created symlink /etc/systemd/system/hibernate.target → /dev/null.
Created symlink /etc/systemd/system/hybrid-sleep.target → /dev/null.
3.观察系统休眠状态，如下：
systemctl status sleep.target
可以看到自动休眠模式已被关闭：
● sleep.target
Loaded: masked (Reason: Unit sleep.target is masked.)
Active: inactive (dead)