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Overview of Storage in an Operating System

1. What is a Partition?

A partition is a logical division of a hard disk or other storage device. Think of a disk as a blank canvas and a partition as a designated area that you prepare for a specific purpose, like a painting sectioned off for different types of artwork.

Partitions allow you to: - Organize data. - Run multiple operating systems on the same physical disk. - Optimize system performance. - Enhance security by isolating different types of data.

2. Why Partition a Disk?

Partitioning a disk is crucial for several reasons: - Separation of Data: You can separate system files from user data, which can help prevent data loss in case the system files become corrupted. - Multiple Operating Systems: You can install different operating systems on separate partitions and choose which one to boot from. - Efficient Management: It helps in organizing data and improves management, especially in large systems. - Backup and Recovery: Easier to back up and restore specific partitions without affecting the entire system.

3. What is a File System?

A file system is a method and data structure that the operating system uses to manage files on a disk. It dictates how data is stored, retrieved, and organized on a partition. Different file systems are optimized for different types of storage devices and use cases.

Common file systems include: - NTFS: Used by Windows systems, known for support for large files and advanced features. - FAT32: An older file system compatible with many devices but limited in file size and partition size. - ext4: Commonly used in Linux systems, supporting large files and offering journaling features for reliability. - HFS+: Used by macOS before APFS, now largely replaced by APFS in newer macOS versions.

Digging Deeper: Storage Terminologies and Tools

1. Disk vs. Partition

  • Disk: The entire storage device, such as an HDD (Hard Disk Drive) or SSD (Solid State Drive).
  • Partition: A section of the disk that can be formatted with a file system and used independently.

2. Primary, Extended, and Logical Partitions

  • Primary Partitions: These are the main partitions that can be created on a disk. A disk can have up to four primary partitions.
  • Extended Partition: A special type of partition that can hold multiple logical partitions. It's used to overcome the four primary partition limit.
  • Logical Partitions: Partitions created within an extended partition. There can be many logical partitions.

3. Master Boot Record (MBR) and GUID Partition Table (GPT)

  • MBR: An older partitioning scheme that supports disks up to 2 TB and allows up to four primary partitions. It contains a bootloader for the OS and partition table information.
  • GPT: A modern partitioning scheme that supports much larger disks and more partitions. It is part of the UEFI standard, replacing BIOS.

4. Commands and Tools

  • fdisk: A command-line utility to manage disk partitions. It works with MBR and allows you to list, create, delete, and modify partitions.

sh sudo fdisk /dev/sda

Here, /dev/sda refers to the first disk in the system. Other disks might be /dev/sdb, /dev/sdc, etc.

  • lsblk: Lists information about all available block devices (disks and partitions). It provides a tree view of the disks and their partitions.

sh lsblk

  • Output typically includes the device name, size, type, and mount point.

    • NAME: The name of the device or partition.
    • MAJ: The major and minor device numbers. These are used by the kernel to identify devices.
    • RM: Indicates whether the device is removable (1 for removable, 0 for non-removable).
    • SIZE: The size of the device or partition.
    • RO: Read-only status (1 for read-only, 0 for writable).
    • TYPE: The type of device (disk, partition, loop device, etc.).
    • MOUNTPOINTS: The directory where the device or partition is mounted, making it accessible to the system.

  • mkfs: Used to create a file system on a partition. For example, to format a partition with the ext4 file system:

sh sudo mkfs.ext4 /dev/sda1

Here, /dev/sda1 represents the partition on which the file system will be created.

  • mount and umount: Used to mount and unmount file systems, respectively. Mounting makes the file system accessible to the OS at a specific directory (mount point).

sh sudo mount /dev/sda1 /mnt

This mounts the partition /dev/sda1 to the /mnt directory.

Understanding Output from Tools

When you use tools like fdisk or lsblk, you'll encounter terms like:

  • /dev/sda: The first disk.
  • /dev/sda1, /dev/sda2: Partitions on the first disk.
  • Size: The size of the disk or partition.
  • Type: Indicates whether it's a primary, extended, or logical partition.
  • Mountpoint: The directory where the partition is mounted, making its file system accessible.