In Linux you have various special files in
/dev. These files are called device files. In
the Unix world accessing hardware is different. There you have a
special file which actually runs a driver which in turn accesses the
hardware. The device file is an interface to the actual system
component. Files under /dev also behave
differently than ordinary files. Below are the most important device
files listed.
fd0 |
First Floppy Drive |
fd1 |
Second Floppy Drive |
hda |
IDE Hard disk / CD-ROM on the first IDE port (Master) |
hdb |
IDE Hard disk / CD-ROM on the first IDE port (Slave) |
hdc |
IDE Hard disk / CD-ROM on the second IDE port (Master) |
hdd |
IDE Hard disk / CD-ROM on the second IDE port (Slave) |
hda1 |
First partition of the first IDE hard disk |
hdd15 |
Fifteenth partition of the fourth IDE hard disk |
sda |
SCSI Hard disk with lowest SCSI ID (e.g. 0) |
sdb |
SCSI Hard disk with next higher SCSI ID (e.g. 1) |
sdc |
SCSI Hard disk with next higher SCSI ID (e.g. 2) |
sda1 |
First partition of the first SCSI hard disk |
sdd10 |
Tenth partition of the fourth SCSI hard disk |
sr0 |
SCSI CD-ROM with the lowest SCSI ID |
sr1 |
SCSI CD-ROM with the next higher SCSI ID |
ttyS0 |
Serial port 0, COM1 under MS-DOS |
ttyS1 |
Serial port 1, COM2 under MS-DOS |
psaux |
PS/2 mouse device |
gpmdata |
Pseudo device, repeater data from GPM (mouse) daemon |
cdrom |
Symbolic link to the CD-ROM drive |
mouse |
Symbolic link to the mouse device file |
null |
Everything pointed to this device will disappear |
zero |
One can endlessly read zeros out of this device |
The mouse can be used in both the Linux console (with gpm) and the X window environment. The two uses can be made compatible if the gpm repeater is used to allow the signal to flow to the X server as shown:
mouse => /dev/psaux => gpm => /dev/gpmdata -> /dev/mouse => X
/dev/ttyS0 (repeater) (symlink)
/dev/ttyS1
Set the repeater protocol to be raw (in /etc/gpm.conf) while
setting X to the original mouse protocol in /etc/X11/XF86Config
or /etc/X11/XF86Config-4.
This approach to use gpm even in X has advantages when the mouse is unplugged inadvertently. Simply restarting gpm with
# /etc/init.d/gpm restart
will re-connect the mouse in software without restarting X.
If gpm is disabled or not installed with some reason, make sure to set X to
read directly from the mouse device such as /dev/psaux. For details, refer
to the 3-Button Mouse mini-Howto at
/usr/share/doc/HOWTO/en-txt/mini/3-Button-Mouse.gz,
man gpm,
/usr/share/doc/gpm/FAQ.gz, and
README.mouse.