自定义登录时的banner

正常登录时的banner内容存储在/etc/banner中，只能存储文本内容，修改后，下次登录即生效；

failsafe模式下的banner内容存储在/etc/banner.failsafe中，只能存储广西内容，修改后，下次登录failsafe时生效。

banner生成工具

在Ubuntu下，可以安装figlet，连接执行如下命令

qige@ubuntu:~$ sudo apt-get install figlet
qige@ubuntu:~$ figlet -h
qige@ubuntu:~$ figlet 6Harmonics
   __   _   _                                  _          
  / /_ | | | | __ _ _ __ _ __ ___   ___  _ __ (_) ___ ___ 
 | '_ \| |_| |/ _` | '__| '_ ` _ \ / _ \| '_ \| |/ __/ __|
 | (_) |  _  | (_| | |  | | | | | | (_) | | | | | (__\__ \
  \___/|_| |_|\__,_|_|  |_| |_| |_|\___/|_| |_|_|\___|___/

示例

示例一：

  _______                     ________        __
 |       |.-----.-----.-----.|  |  |  |.----.|  |_
 |   -   ||  _  |  -__|     ||  |  |  ||   _||   _|
 |_______||   __|_____|__|__||________||__|  |____|
          |__| W I R E L E S S   F R E E D O M
 -----------------------------------------------------
 ATTITUDE ADJUSTMENT (12.09, r36088)
 -----------------------------------------------------
  * 1/4 oz Vodka      Pour all ingredients into mixing
  * 1/4 oz Gin        tin with ice, strain into glass.
  * 1/4 oz Amaretto
  * 1/4 oz Triple sec
  * 1/4 oz Peach schnapps
  * 1/4 oz Sour mix
  * 1 splash Cranberry juice
 -----------------------------------------------------

示例二：

 Thank you for choosing
   __   _   _                                  _          
  / /_ | | | | __ _ _ __ _ __ ___   ___  _ __ (_) ___ ___ 
 | '_ \| |_| |/ _` | '__| '_ ` _ \ / _ \| '_ \| |/ __/ __|
 | (_) |  _  | (_| | |  | | | | | | (_) | | | | | (__\__ \
  \___/|_| |_|\__,_|_|  |_| |_| |_|\___/|_| |_|_|\___|___/

 ---------------------------------------------------------
 ARN Beijing Firmware
 ---------------------------------------------------------
 * Kernel       Dawen Zhang, Yaoyang Wang
 * Application  Yu Zhou, Qige Zhao
 ---------------------------------------------------------