Define major number and minor number ?

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  • Sep 6th, 2006

luey% ls -l sd@3,0:a*

brw-r-----   1 root     sys       32, 24 Oct 14 12:17 sd@3,0:a
crw-r-----   1 root     sys       32, 24 Oct 14 12:17 sd@3,0:a,raw

Major numbers are indexes into the kernel's table of device drivers, associating routines to manipulate the device with the user-visible name for the hardware.

Minor numbers are simply instance numbers for the device -- they tell you how many you have, and which particular unit of the device family you're addressing.

In the above eg: 3 is the major number and

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  • Jul 27th, 2007

Above is wrong. In the example "32,24" would be the major,minor device number.

The major device number indicates the general device class, such as disk, tape, or serial line. The minor device number indicates the specific member within that class.

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Vishal Madamwar

  • Sep 19th, 2011

A major device number identifies the specific device driver required to access a device.
A minor device number identifies the specific unit of the type that the device driver controls.

In the following example, the device file dad@0,0:a refers to major device number 136 and minor device number 8.

# ls -l dad@0*

brw-r----- 1 root sys 136, 8 Sep 23 08:35 dad@0,0:a
crw-r----- 1 root sys 136, 8 Sep 23 12:51 dad@0,0:a,raw

Major number 136 identifies the dad device driver. The dad device driver controls integrated device
electronics (IDE) disk drives. Minor number 8, in this case, identifies Slice 0.

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  • Mar 27th, 2012

Major Number: major number defines the device class.

Minor Number: minor number defines the members in that device class.

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Jamal Daken

  • Mar 21st, 2013

Major number specify the specific device driver for that device.

Minor number specify the specific unit for that device.

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