Linux CLI

🔹 1. Introduction to Linux CLI

• What is the CLI?: Overview of the Command Line Interface

• CLI vs GUI: Differences between Command Line Interface and Graphical User Interface

• Why Use CLI?: Advantages of using the command line (speed, automation, flexibility)

• Accessing the CLI: Using terminal emulators in Linux (gnome-terminal, xterm, Konsole)

• CLI Syntax: Basic structure of commands (command, options, arguments)

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🔹 2. Basic Linux Commands

• pwd (Print Working Directory): Displaying the current directory

• ls (List): Listing files and directories

o ls -l: Detailed listing (permissions, sizes, etc.)

o ls -a: Show hidden files

• cd (Change Directory): Navigating between directories

o cd ~: Going to the home directory

o cd ..: Moving up one directory level

• mkdir (Make Directory): Creating directories

• rmdir (Remove Directory): Removing empty directories

• rm (Remove Files): Deleting files

o rm -r: Remove directories and their contents

• touch: Creating empty files

• cp (Copy): Copying files and directories

• mv (Move): Moving files or renaming them

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🔹 3. File and Directory Permissions

• Understanding Permissions: Read, Write, and Execute permissions (r, w, x)

• chmod (Change Mode): Changing file permissions

o chmod 755: Common permissions for scripts

o chmod u+x filename: Giving execute permission to the user

• chown (Change Ownership): Changing file ownership

o chown user:group filename: Changing file owner and group

• ls -l: Viewing file permissions

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🔹 4. Managing Files and Directories

• Finding Files: Using find to search for files in directories

o find /path/to/search -name filename

• File Compression and Decompression:

o tar (tarballs): Creating and extracting tar files

o zip / unzip: Creating and extracting zip files

o gzip / gunzip: Compressing and decompressing files

• File Editing:

o nano: A simple text editor

o vim: A more advanced text editor

• Viewing Files:

o cat: Display contents of a file

o less: View content page by page

o more: View file content one screen at a time

o head: View the top part of a file

o tail: View the end of a file

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🔹 5. File Searching and Manipulation

• grep (Global Regular Expression Print): Searching within files using patterns

o grep "pattern" filename: Search for a pattern in a file

o grep -r "pattern" directory: Recursive search in a directory

• locate: Finding files using a pre-built index

o locate filename

• find: Search for files based on specific criteria

o find /path -name "*.txt": Find all .txt files in a directory

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🔹 6. Process Management

• ps (Process Status): Viewing active processes

o ps aux: Viewing all running processes

• top: Interactive view of system processes and resource usage

• kill: Terminating processes by PID

o kill <PID>

o killall <process-name>: Killing processes by name

• jobs: Viewing background jobs

• bg: Resuming a job in the background

• fg: Bringing a job to the foreground

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🔹 7. System Monitoring and Resource Usage

• free: Viewing system memory usage

• df (Disk Free): Viewing disk space usage

o df -h: Showing disk usage in human-readable format

• du (Disk Usage): Checking file or directory disk usage

o du -sh: Summary of disk usage in human-readable format

• uptime: Showing system uptime and load

• vmstat: Monitoring virtual memory statistics

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🔹 8. Networking Commands

• ifconfig / ip: Displaying or configuring network interfaces

• ping: Checking network connectivity to a host

• netstat: Viewing network connections and open ports

• curl: Transfer data from or to a server (HTTP requests)

• wget: Download files from the web

• ssh: Secure shell for remote access

o ssh username@hostname: Connecting to a remote system via SSH

• scp (Secure Copy): Copy files between local and remote systems

o scp file user@hostname:/path/to/destination

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🔹 9. Package Management

• APT (Advanced Package Tool): Package manager for Debian-based distributions (Ubuntu, Debian)

o apt update: Updating package index

o apt upgrade: Upgrading installed packages

o apt install package-name: Installing a package

o apt remove package-name: Removing a package

• YUM: Package manager for RPM-based distributions (CentOS, Fedora)

o yum install package-name: Installing packages

o yum update: Updating all packages

• dpkg: Debian package manager (for Debian-based systems)

o dpkg -i package-name.deb: Installing .deb packages

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🔹 10. System Administration

• sudo: Executing commands with superuser privileges

• useradd: Adding a new user to the system

o useradd username

• passwd: Changing a user's password

• usermod: Modifying a user's account settings

o usermod -aG groupname username: Adding a user to a group

• groupadd: Adding new groups

• chroot: Changing the root directory for a process

• reboot / shutdown: Restarting or shutting down the system

• systemctl: Managing system services (starting, stopping, enabling)

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🔹 11. Shell Scripting

• Creating Shell Scripts: Writing and executing shell scripts

o chmod +x script.sh: Making a script executable

• Variables and Functions: Using variables, functions, and arguments

• Control Structures: if, else, while, for, case

• Loops: Writing for, while, and until loops

• Pipes and Redirection: Using |, >, <, >> to manipulate command output

• Scheduling Tasks: Using cron to automate tasks

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🔹 12. Disk Management

• fdisk: Partitioning hard drives

• mount: Mounting filesystems

• umount: Unmounting filesystems

• lsblk: Listing block devices (disks, partitions, etc.)

• parted: Another tool for partitioning disks

• mkfs: Formatting disks with different file systems (e.g., ext4, NTFS)

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🔹 13. User and Group Management

• groupadd: Adding a new group

• groupdel: Deleting a group

• usermod: Modifying user details

• gpasswd: Administering the group password

• chown: Changing ownership of files and directories

• chmod: Changing file permissions

• passwd: Changing user passwords

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🔹 14. Backup and Recovery

• tar: Backing up and compressing files into .tar archives

o tar -czvf archive.tar.gz folder/

• rsync: Efficient file backup and synchronization

o rsync -av source/ destination/

• dd: Disk cloning and backup

o dd if=/dev/sda of=/dev/sdb bs=64K conv=noerror,sync

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🔹 15. Advanced Topics

• SELinux: Security-Enhanced Linux for managing security policies

• Systemd: Managing system services and boot processes

• LVM (Logical Volume Management): Advanced disk management

• Docker: Containerization and managing containerized applications

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🔹 16. Troubleshooting and Diagnostics

• dmesg: Viewing system logs and hardware information

• journalctl: Viewing and analyzing logs in systemd systems

• strace: Tracing system calls and debugging applications

• lsof: Listing open files and their associated processes