🐧 Lecture 7: Disk Partitioning (fdisk)

This lecture covers the process of disk partitioning, the different types of partitions, and the step-by-step procedure for creating, formatting, and mounting a new partition using the fdisk command-line tool.

Partitioning Concepts

• Disk Partitioning: The process of dividing a single physical disk into one or more logical areas.
• HDD vs. SSD:
  • HDD (Hard Disk Drive): Uses mechanical spinning disks. Best for long-term storage at a low cost.
  • SSD (Solid State Drive): Uses flash memory with no moving parts. It's more expensive but provides rapid boot times and fast file access.
• Partition Types:
  • Primary: A bootable partition. A disk can have a maximum of four primary partitions.
  • Extended: A special type of primary partition that cannot hold data itself but can be subdivided.
  • Logical: The partitions created inside an extended partition. This is used to overcome the 4-partition limit.

The 3-Step Process for Using a New Partition

To use a new disk, you must perform three steps:

1. Step 1: Create the Partition: Use a tool like fdisk to define the partition's size and type.
2. Step 2: Format the Partition: Create a filesystem on the partition so the OS can store data on it (e.g., ext4).
3. Step 3: Mount the Partition: Attach the formatted partition to a directory in the filesystem so you can access it.

Using the fdisk Utility

fdisk is a powerful command-line tool for partition management.

• fdisk -l: Lists all disks and their current partition tables.
• fdisk /dev/sdb: Enters the fdisk editing tool for the disk sdb.

Inside the fdisk tool, you use single-letter commands:

• m: Prints the help menu.
• p: Prints the current partition table for the disk you are editing.
• n: Adds a new partition. It will ask you to choose:
  • p for primary
  • e for extended
  • It will then ask for the partition number, first sector (press Enter for default), and last sector or size (e.g., +2048M for 2GB).
• d: Deletes a partition.
• w: Writes all changes to the disk and exits. This is the save-and-quit command.
• q: Quits the tool without saving any changes.

Formatting and Mounting

• partprobe /dev/sdb: After using fdisk, this command tells the kernel to re-read the partition table to see the new changes.
• mkfs -t ext4 /dev/sdb1: Makes a filesystem of type ext4 on the new sdb1 partition.
• mkdir -p /mt/sdb1: Creates a directory to be used as the "mount point".
• mount /dev/sdb1 /mt/sdb1: Attaches the sdb1 partition to the /mt/sdb1 directory.
• df hT: Verifies that the partition is successfully mounted and shows its usage.

---

🐧 Lecture 8: Comprehensive Review and Practical Scenarios

This lecture serves as a final review of all topics and applies them to practical, real-world scenarios.

Topic 1: Core Linux Concepts (Recap)

• Linux: An operating system based on the Linux Kernel.
• Kernel: The core component that communicates with hardware (RAM, CPU, etc.).
• Distribution (Distro): A complete OS made from the Kernel plus a software collection, including GNU tools, a Package Manager, and a Graphical Environment (like Gnome).
• Shell: The program that takes text commands and gives them to the OS.
• Terminal: The window you type commands into.
• Why Linux?: It is Costless, Stable, Reliable, and Highly Secure.

Topic 2: User and Group Management (Recap)

• User Types: Root (full admin), Privileged (uses sudo), and Normal (limited).
• GUI Management: Done via Settings > Users > Unlock.
• CLI User Commands:
  • sudo useradd -m name: Creates user with a home directory.
  • sudo useradd name: Creates user without a home directory.
  • sudo passwd name: Sets the user's password.
  • sudo userdel name: Deletes user but keeps their files.
  • sudo userdel -r name: Deletes user AND their files.
• CLI Group Commands:
  • sudo groupadd name: Creates a new group.
  • sudo usermod -aG group user: Adds a user to a group.
  • groups user: Lists a user's groups.
  • gpasswd -d user group: Removes user from a group.
  • cat /etc/passwd: Lists all users.
  • cat /etc/group: Lists all groups.

Topic 3: File Permissions (Recap)

• Structure: [File Type] [User (rwx)] [Group (rw-)] [Other (r--)].
• File Type: - for file, d for directory.
• Command: chmod.
• Symbolic Mode: Uses u, g, o and +, -, =.
  • Example: chmod g+x file (Adds Execute for Group).
  • Example: chmod u-x file (Removes Execute from User).
  • Example: chmod o-rwx file (Removes All from Other).
• Absolute Mode: Uses numbers (r=4, w=2, x=1).
  • rwx = 4+2+1 = 7
  • rw- = 4+2+0 = 6
  • r-x = 4+0+1 = 5
  • r-- = 4+0+0 = 4
  • --- = 0+0+0 = 0
  • Example: chmod 755 file means rwxr-xr-x.
  • Example: chmod 670 file means rw-rwx---.

Topic 4: Partitioning & Advanced File Commands (Recap)

• Partitioning: Dividing a disk. Max 4 primary partitions. An Extended partition holds Logical partitions (e.g., sda5, sda6).
• 3 Steps: 1) Create (fdisk /dev/sdb), 2) Format (mkfs -t ext4 /dev/sdb1), 3) Mount (mount /dev/sdb1 /data).
• fdisk commands: n (new), p (print), w (write/save), q (quit).
• find: Searches for files.
  • find . -name "Capsules": Finds a file named "Capsules" in the current directory (.).
• grep: Searches inside files.
  • grep Panadol Capsules: Searches for the text "Panadol" inside the "Capsules" file.
• tail -f: Follows a file and shows new lines as they are added.
• echo >>: Appends text to a file.
• uniq: Removes consecutive duplicate lines from a file.
• tar: Archives (zips) and extracts (unzips) files.
  • tar -cvf Books.Rar ...: Creates a verbose file (archive).
  • tar -xvf Books.Rar: Extracts a verbose file (archive).