mkfs is used to build a Linux filesystem on a device, usually a hard disk partition. The device argument is either the device name (e.g. /dev/hda1, /dev/sdb2), or a regular file that shall contain the filesystem. The size argument is the number of blocks to be used for the filesystem.
Formats the drive to FAT32, other formats available are mkfs.bfs, mkfs.ext2, mkfs.ext3, mkfs.ext4, mkfs.minix, mkfs.msdos, mkfs.vfat, mkfs.xfs, mkfs.xiafs etc.
Volume-name sets the volume name (label) of the file system. The volume name can be up to 11 characters long. The default is no label. In this tutorial my volume-name is Ubuntu.
It is typical for fixed disk devices to be partitioned so by default, you are not permitted to create a filesystem across the entire device.
Running $ df after formatting displays this.
You are done and your pen drive has successfully been formatted.