Master Linux Basics: Filesystem, Commands, Users, and Permissions Explained

Operating System Overview

Operating System (OS) is software that manages and controls computer hardware and software resources, running directly on the bare machine. All other software requires the OS to operate.

Linux OS Installation

For Linux installation, see the tutorial at https://blog.csdn.net/huaijiu123/article/details/82083452

Linux Filesystem

/var

: files changed during normal operation, spool files, log files, lock files, temporary files, and page‑formatted files. /home: user files such as configuration, personal data, mail, and cache. A separate directory is created for each user. /proc: virtual files that exist only in memory; they provide process and system information. /bin: essential executable binaries needed at system startup, usable by regular users. /etc: system configuration files (firewall, startup scripts, etc.). /root: home directory of the root (super‑user) account. /dev: device directory; devices are represented as files, allowing uniform read/write access.

Linux Command Operations

Show current directory: pwd Change directory: cd (e.g., cd /path, cd ~, cd .., cd -)

List files: ls (options: ls -l, ls -a, ls -la)

Create directory: mkdir (e.g., mkdir folder, mkdir -p dir1/dir2/dir3)

Remove directory: rmdir (e.g., rmdir folder, rmdir -p folder)

Delete files or directories: rm (e.g., rm -rf path, rm -ri path)

Copy files or directories: cp (e.g., cp -r src dest, cp -ri src dest)

Move/rename: mv (e.g., mv old new)

Create empty file: touch filename Edit file: vi filename View file content: cat filename Show file head: head -n filename Show file tail: tail filename (or tail -f filename for live logs)

Linux Permissions

Linux defines three permissions: read (r), write (w), and execute (x). Use ls -l to view permissions. Example permission string:

drwxr-xr-x 2 root root 4096 Sep 23 2011 bin

d

: directory rwx: owner has read, write, execute r-x: group has read and execute r-x: others have read and execute

Change permissions with chmod. Two modes:

Symbolic mode: use u/g/o and +/‑ with r/w/x (e.g., chmod u+rwx,g+rw,o+r file)

Numeric mode: use three octal digits (e.g., chmod 753 file, chmod 777 file)

Linux Process Management

View processes with ps (e.g., ps -ef | grep keyword) and kill them with kill -9 PID.

Linux System Software Installation

Common installation methods:

tar : extract source packages ( tar -zxvf file.tar.gz, tar -jxvf file.tar.bz2, tar -xvf file.tar)

rpm : Red Hat package manager ( rpm -ivh package.rpm, rpm -qa | grep name, rpm -e package)

yum : resolves dependencies and installs rpm packages automatically.