Whats the diff between /dev/sg0 And /dev/scd0 ???

[Luciano Miguel Ferreira Rocha]

On Sat, May 08, 2004 at 03:25:59PM -0400, Joe(theWordy)Philbrook wrote:
> Whats the diff between /dev/sg0 And /dev/scd0 ???

scd0 is a block device whilst sg0 is a character device. Generically,
block devices can be mounted and are cached, and char devices are for
communication devices, aren't cached nor block aligned, and can't be
mounted.

Specifically, scd* (block) are for cdroms, providing the block access
and commands for ejecting, closing, playing, etc.

sd* (block) are for normal harddisks, providing partitions and some
few commands.

st* (char) are for tape devices (rewind, read, write, etc.).

sg* are for the rest. They accept any scsi command you dare to construct,
and so are used for controlling some esoteric devices or devices that have
no standard interface. Scanners and recorders follow under this one
(recorders, as they also relate to _reading_, have a corresponding scd*
device). They can't be cached and need specific commands by vendor by
action.

/etc/fstab, as it relates to mounting filesystems, should refer only to
block devices (or none, for virtual filesystems).

Regards,
Luciano Rocha