the maldivian linux blog

File systems are not typically created on bare hard drives; rather, they are created on partitions. On Intel-compatible hardware, Linux defaults to using Microsoft-style partition tables. The Microsoft partition scheme allowed up to four partitions to be created on a hard drive. These partitions are referred to as primary partitions. Only one of these partitions may be active at a time; the Microsoft Master Boot Record will try to boot the active primary partition.

Microsoft eventually realized that people might need more than four partitions, so they modified the partitioning system to allow creation of more partitions. To do this, they developed a special type of primary partition, the extended partition. The extended partition is not a functional partition, and no file system can be created on it; rather, it is simply a container for other functional partitions, called logical partitions. In the Microsoft partition scheme, up to four primary partitions can be created, one of which can be an extended partition. Within the extended partition, up to four logical partitions can be created, producing a potential total of seven (three primary and four logical) usable hard drive partitions. Linux extends this scheme slightly by allowing more than four logical partitions to be created in the extended partition

On IDE hardware, Linux supports a total of 63 usable partitions; on SCSI hardware, a maximum of 15 partitions.

Partitions serve many useful purposes. They impose maximum size limits to file systems, making them useful security tools for constraining usage of system resources. Similarly, some other security tools on Linux, such as quotas, are implemented at the level of the partition. Furthermore, partitions make it easy to divide up hard drive space into smaller functional units, simplifying long-term system management.

RHEL/FC typically use a minimum of three partitions to install on Intel-compatible hardware. The first of these is a small partition, /boot. This boot partition should normally be 75 to 100 megabytes in size; it will contain only the essential system files which Linux needs to boot. In the past it was usually set to be much smaller, around 20 megabytes, but now the recommended size has increased so that multiple kernels can be installed simultaneously. The second of these partitions is a swap partition, used to page out programs from RAM. This partition is typically 256 - 512 megabytes in size, though appropriate size will vary with the machine’s intended function and the amount of RAM installed. The third, required, partition is the root partition, /. This partition needs to be large enough to contain all other files that will be installed by RHEL/FC.