Linux Pocket Guide

Disks and Filesystems

df	Display available space on mounted filesystems
mount	Make a disk partition accessible
umount	Unmount a disk partition (make it inaccessible)
fsck	Check a disk partition for errors
sync	Flush all disk caches to disk

Linux systems can have multiple disks or disk partitions. In casual conversation, these are variously called disks, partitions, filesystems, volumes, even directories. We’ll try to be more accurate.

A disk is a hardware device, which may be divided into partitions that act as independent storage devices. Partitions are represented on Linux systems as special files in (usually) the /dev directory. For example, /dev/hda7 could be a partition on your master IDE disk. Some common devices in /dev are:

hda	First IDE bus, master device; partitions are hda1, hda2, …
hdb	First IDE bus, slave device; partitions are hdb1, hdb2, …
hdc	Second IDE bus, master device; partitions are hdc1, hdc2, …
hdd	Second IDE bus, slave device; partitions are hdd1, hdd2, …
sda	First SCSI device; partitions are sda1, sda2, …
sdb	Second SCSI device; partitions are sdb1, sdb2, … Likewise for sdc, sdd, …
ht0	First IDE tape drive (then ht1, ht2, …) with auto-rewind
nht0	First IDE tape drive (then nht1, nht2, …) without auto-rewind
st0	First SCSI tape drive (then st1, st2, …)
scd0	First SCSI CD-ROM drive (then scd1, scd2, …)
fd0	First floppy drive (then fd1, fd2, …), usually mounted on /mnt/floppy

Before a partition can hold files, it is “formatted” by writing a filesystem on it. A filesystem defines how files are ...