[小技巧]Linux的一些信息获取

1. Linux 系统登录之后，显示如下

Last login: Thu Jan 1 00:00:22 UTC 1970 on ttyS0
Linux xxx 4.1.6 #1 PREEMPT Wed Jul 19 13:15:08 CST 2017 armv7l

那么这些信息是哪里获取到的呢，比如Jul19 13：15....

Kernel每次编译的时间在源码的什么位置？

include/generated/compile.h

2. Kernel版本信息存放在源码什么位置？

include/generated/utsrelease.h

3. 如何定制自己的登录前后信息？

/etc/issue, 可以选择在这里做登录提示，或者项目标志打印, 可以选择 l可以看到hostname和tty登录信息

/etc/issue: 登录之前提示信息

/etc/motd: 登录之后提示信息

/etc/issue – escape code

The issue-file (/etc/issue or the file set with the -f option) may contain certain escape codes to display the system name, date and time etc. All escape codes consist of a backslash () immediately followed by one of the letters explained below.

 : Insert the baudrate of the current line.
d : Insert the current date.
s : Insert the system name, the name of the operating system.
l : Insert the name of the current tty line.
m : Insert the architecture identifier of the machine, eg. i486

 : Insert the nodename of the machine, also known as the hostname.
o : Insert the domainname of the machine.

 : Insert the release number of the OS, eg. 1.1.9.
	 : Insert the current time.
u : Insert the number of current users logged in.
U : Insert the string “1 user” or “ users” where is the number of current users logged in.
v : Insert the version of the OS, eg. the build-date etc.

4. 如何查看系统的登录信息和一些操作log？

/var/log/auth.log