Content









8.1

Disks and File Systems





8.1.4

Linux partitions




Linux was originally developed for the
Intel x86 architecture, therefore, it uses the PC partitioning scheme.
Hard drives, currently in use, frequently contain only one partition and
therefore only one file system. Current x86 architecture allows dividing
the hard drive into four primary partitions or three primary partitions
and one extended partition. The extended partition can have multiple
logical partitions defined within it. When Linux is installed on other
computer architectures such as Sunłs SPARC or IBMłs RISC, it uses the
partitioning native to those architectures.
Linux refers to an x86 partition and
associated file system by its device name. Primary partitions 1 through
4 on an EIDE drive are numbered as /dev/hda1 through /dev/hda4. Logical
partitions are numbered starting with /dev/hda5. As an example,
/dev/hda1 would be the first partition of the master drive on the
primary EIDE bus. Partition /dev/hdb2 would be the Slave drive on the
second EIDE bus. EIDE allows a primary and secondary bus and each can
have a master and slave drive. SCSI drives are numbered similarly. As an
example, /dev/sda2 would be the second partition on the first SCSI drive
of the SCSI host adapter or chain. This partition naming scheme for EIDE
and SCSI drives is summarized in Figure
.
Partition Requirements
Linux must have at least one partition
which is the root (/) partition mounted at the root directory. A
standard workstation installation of Red Hat Linux creates a root
partition, a /boot partition, and a swap partition. The root and boot
partitions will be formatted for a particular file system such as ext2
or ext3. The swap partition is not formatted as a user accessible
partition but instead is used only by the OS. During installation, some
administrators choose to divide the hard drive into multiple logical
partitions. The number and function of partitions created depends on
administrative policies and the role the computer will play.
Workstations will typically have few partitions, 2 or 3.Servers may have
a greater number of partitions, 3 to 6 per server. Some of the common
Linux partitions are listed in Figure
. The partition
name and file system name is typically the same as its mount point in
the directory structure. For example, /usr is the mount point for the
user file system and is also referred to as the user partition.