Naming Conventions for Special Files

Special files normally reside in the /dev directory, which is mounted at boot time. By convention, special file names follow the form /dev/rsuffix for raw (character) mode and /dev/suffix for buffered (block) mode. See also "Supported Devices".

The suffix is made up of:

• A string of letters referring to the device driver name, such as sd for a SCSI disk, rd for a RAM disk, hd for an IDE disk or flash for flash,

• Followed by a digit representing the disk unit number, such as 0, 1, 2 and so forth (except for special files not related to file systems, such as tty device files),

• Terminated by a single letter referring to the partition, such as a, b, ... h.

Special care must be taken with partition c. Partition c represents the whole disk and therefore must not be used to support a file system.

Because file systems are based on BSD 4.4 as implemented in FreeBSD 4.1, the same limitations found in FreeBSD 4.1 apply to ChorusOS file system management. According to limitations imposed by FreeBSD, a disk can be divided into a maximum of eight different partitions for IDE and SCSI devices, two partitions for RAM and flash devices. Partitions can be left undefined. Partitions are named using a single character in the range from a to h, each letter corresponding to one of the eight partitions for IDE and SCSI devices. For RAM and flash devices, only partitions a and c are available.

The ChorusOS operating system differs from FreeBSD 4.1 in that the latter does not distinguish between raw devices and block devices. With the ChorusOS operating system both forms of special files are retained for backward compatibility. It is recommended to use the block device.