A Guide to Partitions & Partitioning Drives in Linux

Linux has completely different naming conventions while mounting drives as compared to Windows. /dev/sda,/dev/sdb,/dev/sdc etc. are the conventions in Linux.

Each drive has its own partition table that describes the layout of partitions of the drive. MBR,GPT etc. are the different partition table standards used. The MBR partition scheme is quite old and is rarely used due to limitations like-

  1. It does not allow the configuration of more than four main partitions. Those partitions are called primary partitions.

  2. Disk partitions are limited to 2TB

Every disk can have three kinds of partitions as per the MBR scheme -

  • Primary Partitions - Usually for storing OSes

  • Logical Partitions - Every primary partition may have multiple logical partitions

  • Extended Partitions - A primary partition can be extended with this to overcome the limitation of maximum four primary partitions. These partitions can be found named with the conventions /dev/sda1,/dev/sda2 etc.

(Enter all the commands mentioned below in root or with a sudoers’ user)

Mounting drives in Linux

Running fdisk -l in root lists out the number of drives that are mounted on the system. /dev/sda is usually the hard drive or SSD on which the OS is running. Other external drives can be found ususally at /dev/sdb

df -h may also help locating external drives.

Whenever an external drive is inserted it is usually automatically mounted. To format a drive it must be unmounted first.

Drives can also be mounted with mount /dev/sda /mnt if the drive to be mounted is /dev/sda and the mount location is /mnt.

Formatting drives in Linux

There are two ways to format drives. One is with a graphical interface utility (GParted) or via the terminal.

GParted may be installed with the aptitude package manager supporting OSes by apt-get install gparted

Entering umount /dev/sdc1 in root if sdc1 is the drive mount point, will unmount the external drive. Format the drive with the mkfs utility provided with Linux

    mkfs.ext4 /dev/sdc1 For ext4 file system
    mkfs.vfat /dev/sdc1 For vFat file system
    mkfs.ntfs /dev/sdc1 For NTFS file system

Creating a bootable drive in Linux

The USB drive must be completely formatted before installing. Format the drive to any supported file system. Several GUI based utilities like etcher can be used to format and create bootable drives. Linux and Unix based systems provide the data duplicator(dd) utility to copy binary data to drives.

    dd if=/home/linus/file.iso of=/dev/sdc 
    if - The location of the input file
    of - Location of the mounted drive

Status of dd can be monitored by

    grep -l '^dd$ - Returns the process Id of dd
    kill -USR1 process_id - Shows the status 

After dd has completed transferring the iso to the drive type sync. This is a good practice, since it forces completition of pending disk writes. It flushes the cache.

Partitioning Drives In Linux

Creating a partition

GParted is an excellent utility to partition drives. It can also be done with its command-line version invoked by parted

1.Select the disk to be operated on with select /dev/sdc (within the parted console invoked after typing parted)if the disk to be parted is at /dev/sdc

2.Label the disk with mklabel name.

3.Create the partition

    mkpart logical - Creates a logical partition

Enter the start and end location in megabytes. This will indicate the size of the partition. Eg. Start can be 1 and End can be 1000 indicating a partition of 1 Gb

4.The partition can be formatted with any file system with the mkfs command as explained above.

Removing a partition

1.Invoke the parted utility with parted.

2.Select the disk to be operated on with select /dev/sdc if the disk to be parted is at /dev/sdc

3.rm 1 will remove the first partition from sdc if it has been selected

Resizing a partition

1.Invoke the parted utility with parted.

2.Select the disk to be operated on with select /dev/sdc if the disk to be parted is at /dev/sdc

  1. resizepart will ask for the new start and end to resize the partition.
Recovering a partition

Lost partitions can be recovered by rescue. It asks for the start and end point in Mbs. If any lost partition is found,parted will recover the lost partition.

Chaitanya Rahalkar
Graduate Student

Masters in Cybersecurity student at Georgia Tech.