mknod Post: 23660

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Top Forums UNIX for Dummies Questions & Answers mknod Post 23660 by killerserv on Wednesday 26th of June 2002 08:28:18 PM

06-26-2002

Registered User

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, suppose that version of the MAKEDEV script does not know how to create the /dev/ttyS0 device file. Then you need to use mknod to create it. From looking at the devices.txt file that it should be a character device with major number 4 and minor number 64. So you now know all you need to create the file.

Exp:

Code:

	# 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

As you can see, many more steps are required to create the file. In this example you can see the process required however

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LEARN ABOUT REDHAT

hd

HD(4)							     Linux Programmer's Manual							     HD(4)

NAME

       hd - MFM/IDE hard disk devices

DESCRIPTION

       The  hd*  devices  are block devices to access MFM/IDE hard disk drives in raw mode.  The master drive on the primary IDE controller (major
       device number 3) is hda; the slave drive is hdb.  The master drive of the second controller (major device number 22) is hdc and	the  slave
       hdd.

       General	IDE block device names have the form hdX, or hdXP, where X is a letter denoting the physical drive, and P is a number denoting the
       partition on that physical drive.  The first form, hdX, is used to address the whole drive.  Partition numbers are assigned  in	the  order
       the  partitions	are  discovered, and only non-empty, non-extended partitions get a number. However, partition numbers 1-4 are given to the
       four partitions described in the MBR (the `primary' partitions), regardless of whether they are unused or extended.  Thus, the first  logi-
       cal  partition  will be hdX5.  Both DOS-type partitioning and BSD-disklabel partitioning are supported.	You can have at most 63 partitions
       on an IDE disk.

       For example, /dev/hda refers to all of the first IDE drive in the system; and /dev/hdb3 refers to the third DOS `primary' partition on  the
       second one.

       They are typically created by:

	      mknod -m 660 /dev/hda b 3 0
	      mknod -m 660 /dev/hda1 b 3 1
	      mknod -m 660 /dev/hda2 b 3 2
	      ...
	      mknod -m 660 /dev/hda8 b 3 8
	      mknod -m 660 /dev/hdb b 3 64
	      mknod -m 660 /dev/hdb1 b 3 65
	      mknod -m 660 /dev/hdb2 b 3 66
	      ...
	      mknod -m 660 /dev/hdb8 b 3 72
	      chown root:disk /dev/hd*

FILES

       /dev/hd*

SEE ALSO

       mknod(1), chown(1), mount(8), sd(4)

Linux								    1992-12-17								     HD(4)