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Full Discussion: mknod system call to clone /dev/null
Top Forums Programming mknod system call to clone /dev/null Post 302089367 by blowtorch on Tuesday 19th of September 2006 12:56:32 AM
Old 09-19-2006
nathan,
You are referencing the wrong struct member to get device numbers. You should be referring to st_rdev and not st_dev.

From man stat:
Code:
dev_t    st_dev;      /* ID of device containing */
                           /* a directory entry for this file */
     dev_t    st_rdev;     /* ID of device */
                           /* This entry is defined only for */
                           /* char special or block special files */

Also, if you know the major and the minor device numbers, you can use the makedevice macro to create the device number. The makedevice macro is defined in /usr/include/sys/sysmacros.h. Maybe you could take a look at that file as well.
 

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LEARN ABOUT DEBIAN

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 nonempty, nonextended 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

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

COLOPHON

       This  page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    1992-12-17								     HD(4)
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