4.1. Hardware Utilities
4.1.1. The MAKEDEV Script
Most device files will already be created and will be there
ready to use after you install your Linux system. If by some chance
you need to create one which is not provided then you should first
try to use the MAKEDEV script. This script is
usually located in /dev/MAKEDEV but might also
have a copy (or a symbolic link) in
/sbin/MAKEDEV. If it turns out not to be in
your path then you will need to specify the path to it
explicitly.
In general the command is used as:
# /dev/MAKEDEV -v ttyS0
create ttyS0 c 4 64 root:dialout 0660
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This will create the device file
/dev/ttyS0
with major node 4 and minor node 64 as a character device with
access permissions 0660 with owner root and group dialout.
ttyS0 is a serial port. The major and
minor node numbers are numbers understood by the kernel. The kernel
refers to hardware devices as numbers, this would be very difficult
for us to remember, so we use filenames. Access permissions of 0660
means read and write permission for the owner (root in this case)
and read and write permission for members of the group (dialout in
this case) with no access for anyone else.
4.1.2. The mknod command
MAKEDEV is the preferred way of creating
device files which are not present. However sometimes the
MAKEDEV script will not know about the device
file you wish to create. This is where the mknod
command comes in. In order to use mknod you need
to know the major and minor node numbers for the device you wish to
create. The devices.txt file in the kernel
source documentation is the canonical source of this
information.
To take an example, let us suppose that our version of the
MAKEDEV script does not know how to create the
/dev/ttyS0 device file. We need
to use mknod to create it. We know from looking at the
devices.txt that it should be a character
device with major number 4 and minor number 64. So we now know all
we need to create the file.
# mknod /dev/ttyS0 c 4 64
# chown root.dialout /dev/ttyS0
# chmod 0644 /dev/ttyS0
# ls -l /dev/ttyS0
crw-rw---- 1 root dialout 4, 64 Oct 23 18:23 /dev/ttyS0
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As you can see, many more steps are required to create the file. In
this example you can see the process required however. It is
unlikely in the extreme that the ttyS0 file would not be provided by
the
MAKEDEV script, but it suffices to illustrate
the point.
4.1.3. The lspci command
lspci
TO BE ADDED
4.1.4. The lsdev command
lsdev
TO BE ADDED
4.1.5. The lsusb command
lsusb
TO BE ADDED
4.1.6. The lsraid command
lsraid
TO BE ADDED
4.1.7. The hdparm command
hdparm
TO BE ADDED
4.1.8. More Hardware Resources
More information on what hardware resources the kernel is using
can be found in the /proc directory. Refer to
Section 3.7 in chapter 3.
