Create Partitions and Filesystems Manage MBR and GPT partition tables

Linux lets you divide a physical disk into multiple partitions, each with its own filesystem. For example, on a 2 TB SSD you might allocate 1 TB for Windows (NTFS) and 1 TB for Linux (ext4). Partitioning keeps filesystems separate and lets each OS manage its space independently.

Why Partition a Disk?

• Separate operating systems (e.g., Windows vs. Linux)
• Isolate data, swap, and boot partitions
• Use different partition table formats: MBR (DOS) vs. GPT (modern systems)

1. Viewing Existing Partitions

Use lsblk to list block devices and their partitions:

lsblk

Only entries with TYPE part are actual partitions:

$ lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda       8:0    0   20G  0 disk
├─sda1    8:1    0    1G  0 part /boot
├─sda2    8:2    0   19G  0 part
│ ├─cs-root 253:0  0   17G  0 lvm  /
│ └─cs-swap 253:1  0    2G  0 lvm  [SWAP]
sdb       8:16   0   10G  0 disk
sr0      11:0    1 1024M  0 rom

2. Inspecting the Partition Table with fdisk

To view the partition table on /dev/sda, run:

sudo fdisk --list /dev/sda

Sample output:

Disk /dev/sda: 20 GiB, 21474836480 bytes, 41943040 sectors
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: dos
Disk identifier: 0xb65442dd

Device         Boot    Start      End  Sectors Size Id Type
/dev/sda1      *        2048   2099199  2097152   1G 83 Linux
/dev/sda2      2099200 41943039 39843840  19G  8e Linux LVM

• Disklabel type: dos indicates an MBR partition table.
• Start and End are measured in 512-byte sectors.

3. Creating and Modifying Partitions with cfdisk

cfdisk offers an ncurses interface for partitioning. It’s especially helpful on servers without a GUI.

Steps to Partition /dev/sdb

1. Attach the disk (e.g., sdb) and launch:

   sudo cfdisk /dev/sdb
   

2. Select a label:
   • GPT for modern UEFI systems.
   • DOS for legacy MBR.
3. Create partitions:
   • Navigate to Free Space → New → enter 8G → Enter.
   • Repeat in remaining free space with 2G.
4. Resize or split (optional):
   • Highlight a partition → Resize → enter new size (e.g., 4G).
   • Use freed space to create another partition.

Disk: /dev/sdb
Size: 10 GiB, 10737418240 bytes, 20971520 sectors
Label: gpt, identifier: 42F7FA1E-9398-1741-89AA-477083B71FC3

Device       Start       End    Sectors  Size Type
/dev/sdb1    2048     8390655   8388608   4G Linux filesystem
/dev/sdb2  8390656    16779263   8388608   4G Linux filesystem
/dev/sdb3 16779264    20971486   4192223   2G Linux filesystem

3.1 Setting a Partition Type

The default type is “Linux filesystem.” To mark /dev/sdb3 as swap:

• Highlight sdb3 → Type → select Linux swap → Enter.

You can also choose types like EFI System for UEFI boot partitions or Microsoft reserved for Windows.

3.2 Writing and Quitting

1. Select Write, type yes, and press Enter.
2. Select Quit to exit cfdisk.

4. Verifying the New Partitions

Back in the shell, confirm with lsblk:

lsblk

NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda       8:0    0   20G  0 disk 
├─sda1    8:1    0    1G  0 part /boot
├─sda2    8:2    0   19G  0 part 
│ ├─cs-root 253:0  0   17G  0 lvm  /
│ └─cs-swap 253:1  0    2G  0 lvm  [SWAP]
sdb       8:16   0   10G  0 disk 
├─sdb1    8:17   0    4G  0 part 
├─sdb2    8:18   0    4G  0 part 
└─sdb3    8:19   0    2G  0 part 
sr0      11:0    1 1024M  0 rom  

Now /dev/sdb has three partitions: two 4 GiB data partitions and one 2 GiB swap.

Summary of Common Commands

Links and References

• lsblk(8) — list block devices
• fdisk(8) — partition table manipulator
• cfdisk(8) — curses-based partition editor
• GPT vs. MBR Partition Tables