NAME

mkfs − construct a file system

SYNOPSIS

/etc/mkfs special blocks[:inodes] [gap blocks/cyl]
/etc/mkfs special proto [gap blocks/cyl]

DESCRIPTION

Mkfs constructs a file system by writing on the special file according to the directions found in the remainder of the command line.  If the second argument is given as a string of digits, mkfs builds a file system with a single empty directory on it. The size of the file system is the value of blocks interpreted as a decimal number.  This is the number of physical disk blocks the file system will occupy.  The boot program is left uninitialized. If the optional number of inodes is not given, the default is the number of logical blocks divided by 4. 

If the second argument is a file name that can be opened, mkfs assumes it to be a prototype file proto, and will take its directions from that file. The prototype file contains tokens separated by spaces or new-lines. The first token is the name of a file to be copied onto block zero as the bootstrap program. The second token is a number specifying the size of the created file system in physical disk blocks.  Typically it will be the number of blocks on the device, perhaps diminished by space for swapping.  The next token is the number of inodes in the file system.  The maximum number of inodes configurable is 65500.  The next set of tokens comprise the specification for the root file.  File specifications consist of tokens giving the mode, the user ID, the group ID, and the initial contents of the file.  The syntax of the contents field depends on the mode. 

The mode token for a file is a 6 character string.  The first character specifies the type of the file.  (The characters −bcd specify regular, block special, character special and directory files respectively.)  The second character of the type is either u or − to specify set-user-id mode or not.  The third is g or − for the set-group-id mode.  The rest of the mode is a three digit octal number giving the owner, group, and other read, write, execute permissions (see chmod(1)).

Two decimal number tokens come after the mode; they specify the user and group ID’s of the owner of the file. 

If the file is a regular file, the next token is a path name whence the contents and size are copied.  If the file is a block or character special file, two decimal number tokens follow which give the major and minor device numbers.  If the file is a directory, mkfs makes the entries .  and ..  and then reads a list of names and (recursively) file specifications for the entries in the directory.  The scan is terminated with the token $. 

A sample prototype specification follows:

/stand/diskboot
4872 110
d−−777 3 1
usrd−−777 3 1
sh−−−755 3 1 /bin/sh
kend−−755 6 1
$
b0b−−644 3 1 0 0
c0c−−644 3 1 0 0
$
$

In both command syntaxes, the rotational gap and the number of blocks/cyl can be specified. 

The default will be used if the supplied gap and blocks/cyl are considered illegal values or if a short argument count occurs. 

EXAMPLE

mkfs /dev/fd0 2000 7 50

makes a file system in which 2000 is the total size of the file system to be put on /dev/fd0; 7 is a sector interleave number which is used to stagger the disk blocks for more rapid reading, every 7 blocks, and 50 is a modulo operator that forces the sector interlace number first to allocate all blocks in the first 50 sectors, then the next 50, etc. 

NOTE:  The proper selection of the m and n parameters can improve disk efficiency.  Disks which have full or partial track buffering should specify a m and n of 1 and 1; m and n for other disks must be determined by trial and error as the disk latency is related to rotational latency and cpu speed. 

SEE ALSO

dir(4), fs(4), boot(8). 

BUGS

If a prototype is used, it is not possible to initialize a file larger than 64K bytes, nor is there a way to specify links. 

Version 2.3  —  July 04, 1985