Linux Login相关知识整理
Linux Login相关知识整理
根据以下链接整理：
http://www.tldp.org/LDP/sag/html/major-services.html#TERMINAL-LOGINS
http://www.tldp.org/LDP/sag/html/major-services.html#Network-LOGINS
http://www.tldp.org/LDP/sag/html/login-via-terminal.html
http://en.wikipedia.org/wiki/X_display_manager_(program_type)

1.本文把Login分为terminal login、network login和X环境下的login三种


2.terminal login指来自terminals (via serial lines)或console (when not running X)的login，其流程可以描述为：


3.Network logins work a little differently than normal logins：

• 由于Network logins数量可能很多，不可能为每个login运行一个getty
• instead of a herd of gettys, a single daemon per way of logging in (telnet and ssh have separate daemons) that listens for all incoming login attempts. When it notices one, it starts a new instance of itself to handle that single attempt; the original instance continues to listen for other attempts. The new instance works similarly to getty.

4.X环境下的Login：
In the X Window System, xdm（X display manager） runs as a program that allows the starting of a session on an X server from the same or another computer.