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Full Discussion: Mknod
Operating Systems HP-UX Mknod Post 302199320 by bdittmar on Monday 26th of May 2008 11:29:57 AM
Old 05-26-2008
Mknod

Quote:
Originally Posted by sbn
Hey guys i dont quite understand mknod, can anyone explain it to me and what is its purpose in LVM.

Hello,

mknod - create special files
SYNOPSIS

/sbin/mknod name c major minor

/sbin/mknod name b major minor

/sbin/mknod name p
DESCRIPTION

The mknod command creates the following types of files:

*

Character device special file (first SYNOPSIS form),
*

Block device special file (second SYNOPSIS form),
*

FIFO file, sometimes called a named pipe (third SYNOPSIS form).

name is the path name of the file to be created. The newly created file has a default mode that is readable and writable by all users (0666), but the mode is modified by the current setting of the user's file mode creation mask (see umask(1)).
Character and Block Special Files

Character device special files are used for devices that can transfer single bytes at a time, such as nine-track magnetic tape drives, printers, plotters, disk drives operating in "raw" mode, and terminals. To create a character special file, use the c argument.

Block device special files are used for devices that usually transfer a block of data at a time, such as disk drives. To create a block device special file, use the b argument.

The remaining arguments specify the device that will be accessible through the new special file:

major

The major number specifies the major device type (for example, the device driver number).
minor

The minor number specifies the device location, which is typically, but not always, the unit, drive, and/or line number.

The major and minor values can each be specified in hexadecimal, octal, or decimal, using C language conventions (decimal: no leading zero; octal: leading zero; hexadecimal: leading 0x).

The assignment of major and minor device numbers is specific to each HP-UX system. Refer to the System Administrator manuals supplied with your system for details.

Only users who have appropriate privileges can use mknod to create a character or block device special file.
FIFO files

To create a FIFO (named pipe or buffer) file, use the p argument. You can also use the mkfifo command for this purpose (see mkfifo(1)). All users can use mknod to create FIFO files.
WARNINGS

Access Control Lists

In HFS file systems, optional ACL entries can be added to special files and FIFOs with the chacl command (see chacl(1)). In JFS file systems, optional ACL entries can be added to special files and FIFOs with the setacl command (see setacl(1)). However, system programs are likely to silently change or eliminate the optional ACL entries for these files.

Regards
 

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Unix::Mknod(3pm)					User Contributed Perl Documentation					  Unix::Mknod(3pm)

NAME
Unix::Mknod - Perl extension for mknod, major, minor, and makedev SYNOPSIS
use Unix::Mknod qw(:all); use File::stat; use Fcntl qw(:mode); $st=stat('/dev/null'); $major=major($st->rdev); $minor=minor($st->rdev); mknod('/tmp/special', S_IFCHR|0600, makedev($major,$minor+1)); DESCRIPTION
This module allows access to the device routines major()/minor()/makedev() that may or may not be macros in .h files. It also allows access to the mknod(2) system call. FUNCTIONS
mknod($filename, $mode, $rdev) Creates a block or character device special file named $filename. Must be run as a privileged user, usually root. Returns 0 on success and -1 on failure, like "POSIX::mkfifo" does. $major = major($rdev) Returns the major number for the device special file as defined by the st_rdev field from the stat(3) call. $minor = minor($rdev) Returns the minor number for the device special file as defined by the st_rdev field from the stat(3) call. $rdev = makedev($major, $minor) Returns the st_rdev number for the device special file from the $major and $minor numbers. NOTES
There are 2 other perl modules that implement the mknod(2) system call, but they have problems working on some platforms. "Sys::Mknod" does not work on AIX because it uses the syscall(2) generic system call which AIX does not have. "Mknod" implements S_IFIFO, which on most platforms is not implemented in mknod(1), but rather mkfifo(1) (which is implemented in POSIX perl module). The perl module "File::Stat::Bits" also implements major() and minor() (and a version of makedev() called dev_join). They are done as a program to get the bit masks at compile time, but if major() and minor() are implemented as sub routines, the arugment could be something as simple as an index to a lookup table (and thereby having no decernable relation to its result). BUGS
Running "make test" as non root will not truly test the functions, as in most UNIX like OSes, mknod(2) needs to be invoked by a privelaged user, usually root. SEE ALSO
$ERRNO or $! for the specific error message. File::Stat::Bits, Mknod, POSIX, Sys::Mknod major(9), minor(9), mkfifo(1), mknod(8) ftp://ftp-dev.cites.uiuc.edu/pub/Unix-Mknod AUTHOR
Jim Pirzyk, <pirzyk@uiuc.edu> COPYRIGHT AND LICENSE
Copyright (c) 2005-2008 University of Illinois Board of Trustees All rights reserved. Developed by: Campus Information Technologies and Educational Services, University of Illinois at Urbana-Champaign Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ``Software''), to deal with the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimers. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimers in the documentation and/or other materials provided with the distribution. * Neither the names of Campus Information Technologies and Educational Services, University of Illinois at Urbana-Champaign, nor the names of its contributors may be used to endorse or promote products derived from this Software without specific prior written permission. THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE SOFTWARE. perl v5.14.2 2007-12-23 Unix::Mknod(3pm)
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