Linux Terminologies

Linux Commands: From Basic to Advanced

This post explores essential Linux commands, covering everything from navigating the file system to managing processes and more. It's a journey from basic to advanced usage.

I. Basic File System Navigation

These commands are your bread and butter for navigating the Linux file system:

Command	Description
ls	Lists files and directories in the current directory. Use ls -l for detailed information, ls -a to show hidden files, and ls -h for human-readable file sizes.
cd	Changes the current directory. cd .. goes up one directory, cd ~ goes to your home directory.
pwd	Prints the current working directory.
mkdir	Creates a new directory (e.g., mkdir my_directory). Use mkdir -p path/to/new/directory to create parent directories as needed.
rm	Removes files (e.g., rm my_file.txt). Use rm -r directory to remove a directory and its contents (be very careful with this!). rm -rf forces removal without prompting (use with extreme caution).
cp	Copies files or directories (e.g., cp file1.txt file2.txt, cp -r directory1 directory2).
mv	Moves or renames files or directories (e.g., mv old_file.txt new_file.txt, mv file.txt /path/to/destination/).
cat	Displays file content. Use cat file.txt. For large files use less file.txt or more file.txt.
echo	Prints text to the console (e.g., echo "Hello, world!").

II. Working with Files

Beyond basic manipulation, these commands offer powerful file management:

Command	Description
touch	Creates an empty file (e.g., touch new_file.txt). Also updates file timestamps.
nano/vim/vi	Text editors for creating and editing files.
head	Displays the first few lines of a file (e.g., head -n 10 file.txt for the first 10 lines).
tail	Displays the last few lines of a file (e.g., tail -f file.txt to follow changes in real-time).
wc	Counts words, lines, and bytes in a file (e.g., wc -l file.txt for line count).
grep	Searches for patterns in files (e.g., grep "pattern" file.txt, grep -r "pattern" directory for recursive search).
find	Finds files based on various criteria (e.g., find . -name "file.txt", find . -type d for directories).

III. User and Permissions Management

These commands are crucial for system security:

Command	Description
sudo	Executes a command with superuser privileges.
useradd	Adds a new user (e.g., sudo useradd -m -s /bin/bash newuser).
passwd	Changes a user's password (e.g., sudo passwd newuser).
usermod	Modifies user accounts (e.g., sudo usermod -aG groupname username to add a user to a group).
userdel	Deletes a user (e.g., sudo userdel -r username to remove the user's home directory as well).
chmod	Changes file permissions (e.g., chmod 755 file.txt).
chown	Changes file ownership (e.g., chown user:group file.txt).

IV. Process Management

Control and monitor running processes:

Command	Description
ps	Lists running processes (e.g., ps aux for a detailed view).
top	Displays real-time process activity.
kill	Terminates a process (e.g., kill 1234 to kill process ID 1234). Use kill -9 (SIGKILL) as a last resort.
pkill	Kills processes by name (e.g., pkill firefox).
bg	Puts a process in the background.
fg	Brings a background process to the foreground.
jobs	Lists background jobs.

V. Networking

Commands for network diagnostics and configuration:

Command	Description
ip a or ifconfig	Displays network interface information.
ping	Tests network connectivity to a host.
netstat or ss	Displays network connections, routing tables, and interface statistics.
traceroute	Traces the route packets take to a destination.
dig	DNS lookup utility.
curl or wget	Downloads files from the internet.

VI. System Information

Retrieve information about the system:

Command	Description
uname	Prints system information (e.g., uname -a for all information).
df	Displays disk space usage.
du	Estimates file space usage.
free	Displays memory usage.
uptime	Shows how long the system has been running.
who	Shows who is logged on.

This is a starting point. Linux has a vast array of commands. Use the man command (e.g., man ls) to get detailed information about any command.