修改文件日期戳

$ touch -t yyyyMMddHHmmSS foobar.txt

用rpl命令递归地替换在多个文件中的字符串

$ rpl -Rwd -x'.txt' 'old_string' 'new_string' grades/

/usr/local vs. /opt

What is the difference between their usage? Self-contained programs should be put in /opt; Co-operating heavily with other packages, especially self-compiled, programs should be put in /usr/local.

abstract concept modeling tool --- graphviz

An open source tool for abstract concept modeling, network scaling, or other topology related drawing: graphviz.

Modify User Account Name

Use 'usermod' to modify user account name --- it's easy to modify the user full name, i.e. profile, associated with a user account name.

$ usermod -l new_account_name old_account_name

查看物理内存的Linux指令

在Linux环境中查看物理内存状态的工具：

free

查看网关、DNS的指令

查看网关、路由信息可以用指令route。查看DNS直接用cat指令读文件resolv.conf：

$ cat /etc/resolv.conf