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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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mknod(2)							System Calls Manual							  mknod(2)

NAME
mknod() - make a directory, special, or ordinary file SYNOPSIS
DESCRIPTION
The system call creates a new file named by the path name pointed to by path. The mode of the new file is specified by the mode argument. Symbolic constants that define the file type and file access permission bits are found in the header file and are used to construct the mode argument. The value of the mode argument should be the bit-wise inclusive OR of the values of the desired file type, miscellaneous mode bits, and access permissions. See stat(5) for a description of the components of the file mode. The owner ID of the file is set to the effective-user-ID of the process. If the set-group-ID bit of the parent directory is set, the new file's group ID is set to the group ID of the parent directory. Otherwise, the new file's group ID is set to the effective-group-ID of the process. The file access permission bits of mode are modified by the process's file mode creation mask: for each bit set in the process's file mode creation mask, the corresponding bit in the file's mode is cleared (see umask(2)). In HFS file systems, the new file is created with three base access-control-list (ACL) entries, corresponding to the file access permission bits (see acl(5)). On JFS file systems that support access control lists, when creating a directory or regular file, optional ACL entries are created corresponding to the parent directory's default ACL entries (see aclv(5)). When creating a directory, the parent's default ACL entries are also copied as the new directory's default ACL entries. The dev argument is meaningful only if mode indicates a block or character special file, and is ignored otherwise. It is an implementa- tion- and configuration-dependent specification of a character or block I/O device. The value of dev is created by using the macro defined in The macro takes as arguments the major and minor device numbers, and returns a device identification number which is of type The value and interpretation of the major and minor device numbers are implementation-dependent. For more information, see mknod(5) and the System Administration manuals for your system. Only users having appropriate privileges can invoke for file types other than FIFO files. RETURN VALUE
returns the following values: Successful completion. Failure. The new file is not created. is set to indicate the error. ERRORS
If fails, is set to one of the following values. The directory in which path would be created denies write permission, mode is for a FIFO file and the caller does not have appropriate priv- ileges. A component of the path prefix denies search permission. The user's or group's disk quota block or inode limit has been reached for this file system. The named path already exists. The path argument points outside the process's allocated address space. The reliable detection of this error is imple- mentation dependent. Too many symbolic links were encountered in translating the path name. The length of the specified path name exceeds bytes, or the length of a component of the path name exceeds bytes while is in effect. The path argument is null. A component of the path prefix does not exist. Not enough space on the file system. A component of the path prefix is not a directory. The effective-user-ID of the process does not match that of a user who has appropriate privileges, and the file type is not FIFO special. The directory in which the file is to be created is located on a read-only file system. AUTHOR
was developed by AT&T and HP. SEE ALSO
mknod(1M), acl(2), chmod(2), exec(2), mkdir(2), setacl(2), umask(2), acl(5), aclv(5), mknod(5), stat(5), types(5). STANDARDS CONFORMANCE
mknod(2)
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