MKNOD(1) MKNOD(1)
NAME
mknod - make block or character special files
SYNOPSIS
mknod [options] name {bc} major minor
mknod [options] name p
GNU options (shortest form): [-m mode] [--help] [--ver-
sion] [--]
DESCRIPTION
mknod creates a FIFO (named pipe), character special file,
or block special file with the specified name.
A special file is a triple (boolean, integer, integer)
stored in the filesystem. The boolean chooses between
character special file and block special file. The two
integers are the major and minor device number.
Thus, a special file takes almost no place on disk, and is
used only for communication with the operating system, not
for data storage. Often special files refer to hardware
devices (disk, tape, tty, printer) or to operating system
services (/dev/null, /dev/random).
Block special files usually are disk-like devices (where
data can be accessed given a block number, and e.g. it is
meaningful to have a block cache). All other devices are
character special files. (Long ago the distinction was a
different one: I/O to a character special file would be
unbuffered, to a block special file buffered.)
The mknod command is what creates files of this type.
The argument following name specifies the type of file to
make:
p for a FIFO
b for a block (buffered) special file
c for a character (unbuffered) special file
The GNU version of mknod allows u (`unbuffered') as a syn-
onym for c.
When making a block or character special file, the major
and minor device numbers must be given after the file type
(in decimal, or in octal with leading 0; the GNU version
also allows hexadecimal with leading 0x). By default, the
mode of created files is 0666 (`a+rw') minus the bits set
in the umask.
GNU fileutils 4.0 November 1998 1
MKNOD(1) MKNOD(1)
OPTIONS
-m mode, --mode=mode
Set the mode of created files to mode, which can be
symbolic as in chmod(1) and then uses the default
mode as the point of departure.
GNU STANDARD OPTIONS
--help Print a usage message on standard output and exit
successfully.
--version
Print version information on standard output, then
exit successfully.
-- Terminate option list.
CONFORMING TO
POSIX does not describe this command as it is nonportable,
and recommends using mkfifo(1) to make FIFOs. SVID has a
command /etc/mknod with the above syntax, but without the
mode option.
NOTES
On a Linux system (version 1.3.22 or newer) the file
/usr/src/linux/Documentation/devices.tex contains a list
of devices with device name, type, major and minor number.
The present page describes mknod as found in the fileu-
tils-4.0 package; other versions may differ slightly.
Mail corrections and additions to aeb@cwi.nl. Report bugs
in the program to fileutils-bugs@gnu.ai.mit.edu.
SEE ALSO
chmod(1), mkfifo(1), mknod(2)
GNU fileutils 4.0 November 1998 2