Appendix E. An Introduction to Disk Partitions

115

N

The final number denotes the partition. The first four (primary or extended) partitions are num 

bered

1

through

4

. Logical partitions start at

5

. So, for example,

/dev/hda3

is the third primary

or extended partition on the first IDE hard disk, and

/dev/sdb6

is the second logical partition

on the second SCSI hard disk.

Note

There is no part of this naming convention that is based on partition type; unlike DOS/Windows, all

partitions can be identified under Red Hat Linux. Of course, this does not mean that Red Hat Linux

can access data on every type of partition, but in many cases it is possible to access data on a

partition dedicated to another operating system.

Keep this information in mind; it will make things easier to understand when you are setting up the

partitions Red Hat Linux requires.

E.1.6. Disk Partitions and Other Operating Systems

If your Red Hat Linux partitions will be sharing a hard disk with partitions used by other operat 

ing systems, most of the time you will have no problems. However, there are certain combinations of

Linux and other operating systems that require extra care. Information on creating disk partitions com 

patible with other operating systems is available in several HOWTOs and Mini HOWTOs, available

on the Red Hat Linux Documentation CD in the

HOWTO

and

HOWTO/mini

directories. In particular,

the Mini HOWTOs whose names start with

Linux+

are quite helpful.

Note

If Red Hat Linux/x86 will coexist on your machine with OS/2, you must create your disk partitions with

the OS/2 partitioning software    otherwise, OS/2 may not recognize the disk partitions. During

the installation, do not create any new partitions, but do set the proper partition types for your Linux

partitions using the Linux fdisk.

E.1.7. Disk Partitions and Mount Points

One area that many people new to Linux find confusing is the matter of how partitions are used and

accessed by the Linux operating system. In DOS/Windows, it is relatively simple: Each partition gets

a "drive letter." You then use the correct drive letter to refer to files and directories on its corresponding

partition.

This is entirely different from how Linux deals with partitions and, for that matter, with disk storage

in general. The main difference is that each partition is used to form part of the storage necessary to

support a single set of files and directories. This is done by associating a partition with a directory

through a process known as mounting. Mounting a partition makes its storage available starting at the

specified directory (known as a mount point).

For example, if partition

/dev/hda5

were mounted on

/usr

, that would mean that all

files and directories under

/usr

would physically reside on

/dev/hda5

. So the file

/usr/share/doc/FAQ/txt/Linux FAQ

would be stored on

/dev/hda5

, while the file

/etc/X11/gdm/Sessions/Gnome

would not.

Continuing our example, it is also possible that one or more directories below

/usr

would be

mount points for other partitions. For instance, a partition (say,

/dev/hda7

) could be mounted on