LINUX ALLOCATED DEVICES

Major and Minor Device List

This list is the Linux Device List, the official registry of allocated device numbers and /dev directory nodes for the Linux operating system. I have collected and written this information with the help of my experience and various other sources.

This document is included by reference into the Filesystem Hierarchy Standard (FHS) and is for free use only.

The symbol {!!} means the allocation is obsolete and scheduled for removal once kernel version 2.6 (or equivalent) is released. Some of these allocations have already been removed.

I do not have any information about these devices beyond what appears on this list. Any such information requests will be deleted without reply.

0 Unnamed devices (e.g. non-device mounts)
0 = reserved as null device number
See block major 144, 145, 146 for expansion areas.

1 char Memory devices
1 = /dev/mem Physical memory access
2 = /dev/kmem Kernel virtual memory access
3 = /dev/null Null device
4 = /dev/port I/O port access
5 = /dev/zero Null byte source
6 = /dev/core OBSOLETE - replaced by /proc/kcore
7 = /dev/full Returns ENOSPC on write
8 = /dev/random Nondeterministic random number gen.
9 = /dev/urandom Faster, less secure random number gen.
10 = /dev/aio Asynchronous I/O notification interface
11 = /dev/kmsg Writes to this come out as printk's
12 = /dev/oldmem Used by crashdump kernels to access
the memory of the kernel that crashed.
1 block RAM disk
0 = /dev/ram0 First RAM disk
1 = /dev/ram1 Second RAM disk
...
250 = /dev/initrd Initial RAM disk {!!}

Older kernels had /dev/ramdisk (1, 1) here.
/dev/initrd refers to a RAM disk which was preloaded
by the boot loader; newer kernels use /dev/ram0 for
the initrd.

2 char Pseudo-TTY masters
0 = /dev/ptyp0 First PTY master
1 = /dev/ptyp1 Second PTY master
...
255 = /dev/ptyef 256th PTY master

Pseudo-tty's are named as follows:
* Masters are "pty", slaves are "tty";
* the fourth letter is one of pqrstuvwxyzabcde indicating
the 1st through 16th series of 16 pseudo-ttys each, and
* the fifth letter is one of 0123456789abcdef indicating
the position within the series.