mount_mfs(8)
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MOUNT_MFS(8) NetBSD System Manager's Manual MOUNT_MFS(8)
NAME
mount_mfs - mount a memory based file system
SYNOPSIS
mount_mfs [-N] [-a maxcontig] [-b block-size] [-c cpg] [-d rotdelay] [-e
maxbpg] [-f frag-size] [-g groupname] [-i bytes-per-inode] [-m
free-space] [-n rotational-positions] [-o options] [-p
permissions] [-s size] [-u username] special node
DESCRIPTION
mount_mfs is used to build a file system in virtual memory and then mount
it on a specified node. mount_mfs exits and the contents of the file
system are lost when the file system is unmounted. If mount_mfs is sent
a signal while running, for example during system shutdown, it will at-
tempt to unmount its corresponding file system. special is ignored.
Options with numeric arguments may contain an optional (case-insensitive)
suffix:
b Bytes; causes no modification. (Default)
k Kilo; multiply the argument by 1024
m Mega; multiply the argument by 1048576
g Giga; multiply the argument by 1073741824
The following options define the general layout policies.
-N Causes the memory file system parameters to be printed out
without really mounting the memory file system.
-a maxcontig
This specifies the maximum number of contiguous blocks that
will be laid out before forcing a rotational delay (see the
-d option). The default value is 8. See tunefs(8) for more
details on how to set this option.
-b block-size
The block size of the file system, in bytes. It must be a
power of two. The smallest allowable size is 4096 bytes.
The default size depends upon the size of the file system:
file system size block-size
< 20 MB 4 KB
< 1024 MB 8 KB
>= 1024 MB 16 KB
-c cpg The number of cylinders per cylinder group in a file system.
The default is to compute the maximum allowed by the other
parameters. This value is dependent on a number of other pa-
rameters, in particular the block size and the number of
bytes per inode.
-d rotdelay
This specifies the expected time (in milliseconds) to service
a transfer completion interrupt and initiate a new transfer
on the same disk. The default is 0 milliseconds. See
tunefs(8) for more details on how to set this option.
-e maxbpg This indicates the maximum number of blocks any single file
can allocate out of a cylinder group before it is forced to
begin allocating blocks from another cylinder group. The de-
fault is about one quarter of the total blocks in a cylinder
group. See tunefs(8) for more details on how to set this op-
tion.
-f frag-size
The fragment size of the file system in bytes. It must be a
power of two ranging in value between block-size/8 and block-
size. The optimal block-size:frag-size ratio is 8:1. Other
ratios are possible, but are not recommended, and may produce
unpredictable results. The default size depends upon the
size of the file system:
file system size frag-size
< 20 MB 0.5 KB
< 1024 MB 1 KB
>= 1024 MB 2 KB
-g groupname
This specifies the group name or group id of the root inode
of the file system.
-i bytes-per-inode
This specifies the density of inodes in the file system. If
fewer inodes are desired, a larger number should be used; to
create more inodes a smaller number should be given. The de-
fault is to create an inode for every (4 * frag-size) bytes
of data space:
file system size bytes-per-inode
< 20 MB 2 KB
< 1024 MB 4 KB
>= 1024 MB 8 KB
-m free-space
The percentage of space reserved from normal users; the mini-
mum free space threshold. The default value used is 5%. See
tunefs(8) for more details on how to set this option.
-n rotational-positions
Determines how many rotational time slots there are in one
revolution of the disk.
-o Options are specified with a -o flag followed by a comma sep-
arated string of options. See the mount(8) man page for pos-
sible options and their meanings.
-p permissions
This specifies the permissions of the root inode of the file
system.
-s size The size of the file system in sectors. An `s' suffix will
be interpreted as the number of sectors (the default). All
other suffixes are interpreted as per other numeric argu-
ments, except that the number is converted into sectors by
dividing by the sector size (as specified by -S secsize) af-
ter suffix interpretation.
-u username
This specifies the user name or user id of the root inode of
the file system.
NOTES
The owner and group ids of the root node of the new file system are set
to the effective uid and gid of the user mounting the file system.
EXAMPLES
Mount a 32 MB mfs on /tmp:
mount_mfs -s 32m swap /tmp
SEE ALSO
disktab(5), fs(5), disklabel(8), diskpart(8), dumpfs(8), fsck_ffs(8),
fsirand(8), mount(8), newfs(8), tunefs(8)
M. McKusick, W. Joy, S. Leffler, and R. Fabry, "A Fast File System for
UNIX,", ACM Transactions on Computer Systems 2, 3, pp 181-197, August
1984, (reprinted in the BSD System Manager's Manual).
HISTORY
The mount_mfs command appeared in 4.2BSD.
NetBSD 1.6 May 21, 2002 3
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