Disks

A disk is a mass storage device which we can write to and read from.

SCSI

Small Computer System Interface
Pronounced scuzzy.
It is a protocol that allows communicaton between printers, scanners and other peripherals in addition to harddisks.
The /sda/ device that is the most common designation for the harddisk in Linux systems stands for SCSI disk.

Disk schematic

The following diagram represents the basic anatomy of a disk device.

A disk is divided up into partitions which are subsections of the overall disk. The kernel presents each partition as a block device as it would with an entire disk.
The disk dedicates a small part of its contents to a partition table: this defines the different partitions that comprise the total disk space.
The filesystem is a database of files and directories: this comprises the bulk of the partition and is what you interact with in user space when reading and writing data.

Partitioning disks

Viewing current partitions

Whenever you install a Linux distribution on a real or virtual machine, you must partition the drive. There are three main tools that people choose from: parted, g(raphical)parted, fdisk.

We can use parted -l to view the partition table for the current machine:

Model: SKHynix_HFS512GDE9X081N (nvme)
Disk /dev/nvme0n1: 512GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  513MB   512MB   fat32              boot, esp
 2      513MB   30.5GB  30.0GB  ext4
 3      30.5GB  512GB   482GB   ext4

We can use fdisk -l to get slightly more info:

disk /dev/nvme0n1: 476.94 GiB, 512110190592 bytes, 1000215216 sectors
Disk model: SKHynix_HFS512GDE9X081N                 
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 08175E77-CB9F-C34A-9032-DF29A3F8F0FE

Device            Start        End   Sectors   Size Type
/dev/nvme0n1p1     2048    1001471    999424   488M EFI System
/dev/nvme0n1p2  1001472   59594751  58593280  27.9G Linux filesystem
/dev/nvme0n1p3 59594752 1000214527 940619776 448.5G Linux filesystem

The two tools disclose the following information:

So my main harddrive is /dev/nvme0n1 (equivalent to and it has the standard three partitions:

Boot partition (/dev/nvme0n1p1)
Root dir (/dev/nvme0n1p2)
Home dir (/dev/nvme0n1p3)

! To cover

What is gpt/uefi/efi ext-4 and dos etc

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