Managing Disk Partitions

Introduction

• Managing partitions in Linux is a critical system administration task that involves dividing physical storage devices into logical sections called partitions.
• Proper partition management ensures efficient disk usage, better performance, improved security, and reliable system operation.
• Partitioning is essential for organizing disk storage in Linux. It allows us to efficiently allocate space for the operating system, swap, data storage, and other purposes. 

Disk Storage and Devices

• In Linux, storage devices such as hard disks and solid-state drives are treated as files and are usually located in the /dev directory.
• Storage devices in Linux are represented by device files.
• Disk devices are commonly named
  • HDD/SSD:/dev/sda, /dev/sdb for SATA, SCSI, and USB disks
  • /dev/nvme0n1 for NVMe(Non-Volatile Memory Express) SSDs
• Each partition on a disk is represented by a number
  • Partitions: /dev/sda1, /dev/sda2, etc.
• Linux uses file systems like ext4(Fourth Extended File System), xfs(X File System), and btrfs(B-tree File System) to organize data on partitions. 
• Storage types in Linux are –
  • HDD (Hard Disk Drives): It is a spinning disk part and is slower.
  • SSD (Solid-State Drives): It is faster, with no moving parts, unlike HDD.
  • NVMe (Non-Volatile Memory Express): It is a high-speed SSD and an advanced form of SSD.

Tools/Commands for Disk Management

• fdisk: Partition disks using MBR(Master Boot Record) or GPT(GUID Partition Table).
• parted: Partition disks, especially GPT.
• lsblk: List block devices and their partition layouts.
• blkid: View UUIDs(Universal Unique Identifier) and filesystem types of partitions.

Partition Disk Layout

• A disk can be logically divided into several partitions; each must be formatted with a filesystem (e.g., ext4, xfs, NTFS[New Technology File System]) as needed.
• The common partition types used are:-
  • Primary Partition: Up to 4 partitions in MBR(Master Boot Record) in old systems.
  • Extended Partition: A container for logical partitions (MBR) in old systems.
  • Logical Partition: Partitions within the extended partition in old systems.
  • EFI(Extensible Firmware Interface) System Partition (ESP): Required for UEFI(Unified Extensible Firmware Interface) boot (GPT) in modern systems.

MBR and GPT Partitions

MBR (Master Boot Record)

• MBR is a Legacy partitioning scheme, which means that MBR is an older partitioning scheme used on traditional BIOS-based systems or earlier computer systems, but has limitations compared to modern methods. The partitioning system was designed for older hardware and firmware (BIOS-based systems). It is still supported today for compatibility reasons. It has technical limitations that newer schemes have improved upon.
• MBR is an old, still usable, but largely replaced by more advanced solutions.
• MBR has several characteristics:
  • Supports a maximum disk partition size up to 2 TB.
  • This stores partition data in a single sector (prone to corruption).
  • Allows a maximum of 4 primary partitions.
  • One primary partition can be an extended partition.
  • Extended partitions can contain multiple logical partitions.
  • Stores partition information in the first sector of the disk.
  • It lacks advanced features like redundancy and error checking.
  • It is not suitable for modern UEFI (Unified Extensible Firmware Interface) systems.

GPT (GUID Partition Table):

Creating MBR Partitions

• MBR partitions are commonly created using the fdisk utility.

Step1 : Use the fdisk command first by the administrator as:-

Step2 : Now, create a new partition using the following:

• • Press n to create a partition.
  • Select the primary partition first, and then the extended partition we want to create.
  • Now, specify the partition number and size as needed.

Step3 : Now, save changes:

• • Press w to write/save the partition table.
  • After partition creation, a file system is created using commands like mkfs.ext4. The partition is then mounted to a directory.

Now, Creating MBR Extended and Logical Partitions

• MBR allows only four primary partitions. Therefore, to overcome this limitation, an extended partition is used.
• An extended partition –
  • Acts as a container for logical partitions
  • Counts as one of the four primary partitions
• Logical partitions –
  • They are created inside the extended partition
  • Can be many in number of desired size.
• Partition Created Process –

Step1 : Create an extended partition first :

• • For this, Use fdisk and press n.
  • Select e for an extended partition.

Step2 : Now, add/create logical partitions inside extended partitions:

• • Within the extended partition, we create multiple logical partitions by pressing n and selecting logical options.
  • Each logical partition is formatted and mounted separately after its creation.

Step3 : Write desired changes:

$ sudo partprobe (press enter)    # Inform the kernel of partition changes

Managing GPT Partitions

• GPT partitions are managed using tools such as gdisk or parted.

Step1 : Select the disk and use the parted command to create a partition

Step2 : Creating new partitions with specific sizes with a new GPT desired disk label

Step3 : Create a partition type and size using GUIDs and write/save changes to disk 

Step4 : To verify the partition table

Working with SSD

• SSD devices differ from HDDs because they use flash memory instead of spinning disks.
• Partition alignment is essential for performance in SSDs. 
• TRIM support helps maintain SSD speed and lifespan. Linux supports TRIM using the fstrim command.
• Modern Linux file systems like ext4 and xfs automatically optimize for SSDs.

For Optimizing SSD Usage

• • Add discard or use fstrim command for TRIM support.

Adding a Swap Partition

Steps to Add Swap Partitions:

Step1 : Create a swap partition

• • • Use fdisk or parted command to create a new partition.
    • Set the partition type to swap (code 82 in MBR).

Step2 : Format the created partition using mkswap

Step3 : Enable/activate the swap partition using swapon

Step4 : Make it persistent using /etc/fstab for permanent activation.

• • • Add it to /etc/fstab
      /dev/sdX2 none swap sw 0 0

Encrypted Partitions

• Encrypted partitions protect sensitive data by converting it into an unreadable format without proper authentication.
• Encryption ensures that unauthorized users cannot access data stored on a disk.
• A common encryption tool is LUKS (Linux Unified Key Setup), an industry-standard disk encryption, which is used for this purpose.
• Encryption ensures data confidentiality and compliance with security standards.
• Encrypted partitions provide strong security without affecting normal system usage significantly.

Configuring Encrypted Partitions

Steps to Encrypt a Partition Using LUKS:

Step1 : For this, we require a passphrase or key file. The partition is encrypted using cryptsetup luksFormat, i.e., install cryptsetup

Step2 : Initialize the partition for encryption

Step3 : The encrypted partition is opened using cryptsetup open

Step4 : Format the partition. A file system is created on the encrypted device. 

Step5 : Mount the encrypted partition to a directory

Step6 : Make it persistent

Add an entry in /etc/crypttab

Update /etc/fstab:

Summary of Commands Used in Managing Disk Partitions