/etc/motd and /etc/issue
Bash offers an option to include messages in the /etc/motd and the /etc/issue files. Messages in /etc/motd display after a user has successfully logged in to a shell.用户登录shell之后显示的信息 (Notice that users in a graphical environment do not see its contents after a graphical login.图形登录界面看不到这个信息提示) Using /etc/motd can be a convenient way for system administrators to inform users.
Another way to send information to users is by using /etc/issue. The contents of this file display before the user logs in. This provides an excellent means of specifying specific login instructions to users who are not logged in yet. 这个是在用户登录之前显示的信息。
原文：http://www.cnblogs.com/rusking/p/5586812.html