Third Course 2015.3.13

1. Command ls

-L Show more information

-A view hidden files or directories

-D only look at the directory itself, not list files and directories under directory

-t list files in chronological order

2. Directory structure (refer to http://yangrong.blog.51cto.com/6945369/1288072)

/bin,/sbin,/usr/bin,/usr/sbin the directory where the command is placed, Sbin is the command that Superuser root can use

/boot Linux kernel and the file directory required by the boot system program

/dev Stores external Linux devices

/etc configuration file directory

/home User House Directory command: Useradd

/lib command: #ldd/bin/ls//To determine which shared library files are required for a command, add the "-V" option to display details

/OPT is a directory of some large software or special software, such as Oracle

/proc System Kernel Mapping

echo 1 >/proc/sys/net/ipv4/icmp_echo_ignore_all//Disable ping on host

/root Root User's home directory

/sys

The/sys/class contains all the device types registered in kernel, linked to devices

/sys/dev maintains a list of primary and secondary numbers by character device and block device, linked to device

The/sys/device four global device architecture, which contains all the discovered physical devices registered on various buses, is the kernel

The hierarchical representation model of all devices in the system is also the most important directory structure of/sys file system management equipment.

/sys/kernel stores all the adjustable parameters in the kernel

/tmp temp file

/USR User program storage directory, similar to the Win Programs Files folder

/var stores things that are constantly expanding, and we are accustomed to placing directories that are often modified in this directory, including various log files.

3. Use of the environment variable path

echo $PATH can view the value of the system's environment variable path and use the which command to see the absolute path of a command

Path= $PATH:/tmp So we can use the executable file under/tmp as the command

To make the path permanent, you need to add it to the/etc/profile, restart it, or run the command directly: Source/etc/profile

This article is from the "Rhythm" blog, make sure to keep this source http://rhythm.blog.51cto.com/2800158/1620668

Third Course 2015.3.13