系统设置/登录屏幕

From KDE Wiki Sandbox

Convenience

If you don't want to type your username and password during login, you can check the Enable Auto-login box here, then select the user you want to auto-login with, and hit Apply. Remember, though, that anyone who can physically access your computer or laptop will also have instant access to all your data. You need to make a risk assessment before using this facility.