1.\" $NetBSD: mount_mfs.8,v 1.12 2003/09/11 12:21:01 dsl Exp $ 2.\" 3.\" Copyright (c) 1983, 1987, 1991, 1993, 1994 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)newfs.8 8.6 (Berkeley) 5/3/95 31.\" 32.Dd September 11, 2003 33.Dt MOUNT_MFS 8 34.Os 35.Sh NAME 36.Nm mount_mfs 37.Nd mount a memory based file system 38.Sh SYNOPSIS 39.Nm mount_mfs 40.Op Fl N 41.Op Fl a Ar maxcontig 42.Op Fl b Ar block-size 43.Op Fl d Ar rotdelay 44.Op Fl e Ar maxbpg 45.Op Fl f Ar frag-size 46.Op Fl g Ar groupname 47.Op Fl i Ar bytes-per-inode 48.Op Fl m Ar free-space 49.Op Fl n Ar inodes 50.Op Fl o Ar options 51.Op Fl p Ar permissions 52.Op Fl s Ar size 53.Op Fl u Ar username 54.Ar special node 55.Sh DESCRIPTION 56.Nm 57is used to build a file system in virtual memory and then mount it 58on a specified node. 59.Nm 60exits and the contents of the file system are lost 61when the file system is unmounted. 62If 63.Nm 64is sent a signal while running, 65for example during system shutdown, 66it will attempt to unmount its 67corresponding file system. 68.Ar special 69is ignored. 70.Pp 71Options with numeric arguments may contain an optional (case-insensitive) 72suffix: 73.Bl -tag -width 3n -offset indent -compact 74.It b 75Bytes; causes no modification. 76(Default) 77.It k 78Kilo; multiply the argument by 1024 79.It m 80Mega; multiply the argument by 1048576 81.It g 82Giga; multiply the argument by 1073741824 83.El 84.Pp 85The following options define the general layout policies. 86.Bl -tag -width Fl 87.It Fl N 88Causes the memory file system parameters to be printed out 89without really mounting the memory file system. 90.It Fl a Ar maxcontig 91This specifies the maximum number of contiguous blocks that will be 92laid out before forcing a rotational delay (see the 93.Fl d 94option). 95The default value is 8. 96See 97.Xr tunefs 8 98for more details on how to set this option. 99.It Fl b Ar block-size 100The block size of the file system, in bytes. 101It must be a power of two. 102The smallest allowable size is 4096 bytes. 103The default size depends upon the size of the file system: 104.Pp 105.Bl -tag -width "file system size" -compact -offset indent 106.It Sy "file system size" 107.Ar block-size 108.It \&\*[Lt] 20 MB 1094 KB 110.It \&\*[Lt] 1024 MB 1118 KB 112.It \&\*[Gt]\&= 1024 MB 11316 KB 114.El 115.It Fl d Ar rotdelay 116This specifies the expected time (in milliseconds) to service a transfer 117completion interrupt and initiate a new transfer on the same disk. 118The default is 0 milliseconds. 119See 120.Xr tunefs 8 121for more details on how to set this option. 122.ne 1i 123.It Fl e Ar maxbpg 124This indicates the maximum number of blocks any single file can 125allocate out of a cylinder group before it is forced to begin 126allocating blocks from another cylinder group. 127The default is about one quarter of the total blocks in a cylinder group. 128See 129.Xr tunefs 8 130for more details on how to set this option. 131.It Fl f Ar frag-size 132The fragment size of the file system in bytes. 133It must be a power of two ranging in value between 134.Ar block-size Ns /8 135and 136.Ar block-size . 137The optimal 138.Ar block-size : Ns Ar frag-size 139ratio is 8:1. 140Other ratios are possible, but are not recommended, 141and may produce unpredictable results. 142The default size depends upon the size of the file system: 143.Pp 144.Bl -tag -width "file system size" -compact -offset indent 145.It Sy "file system size" 146.Ar frag-size 147.It \&\*[Lt] 20 MB 1480.5 KB 149.It \&\*[Lt] 1024 MB 1501 KB 151.It \&\*[Gt]\&= 1024 MB 1522 KB 153.El 154.It Fl g Ar groupname 155This specifies the group name or group id of the root 156inode of the file system. 157.It Fl i Ar bytes-per-inode 158This specifies the density of inodes in the file system. 159If fewer inodes are desired, a larger number should be used; 160to create more inodes a smaller number should be given. 161The default is to create an inode for every 162.Pq 4 * Ar frag-size 163bytes of data space: 164.Pp 165.Bl -tag -width "file system size" -compact -offset indent 166.It Sy "file system size" 167.Ar bytes-per-inode 168.It \&\*[Lt] 20 MB 1692 KB 170.It \&\*[Lt] 1024 MB 1714 KB 172.It \&\*[Gt]\&= 1024 MB 1738 KB 174.El 175.It Fl m Ar free-space 176The percentage of space reserved from normal users; the minimum free 177space threshold. 178The default value used is 5%. 179See 180.Xr tunefs 8 181for more details on how to set this option. 182.It Fl n Ar inodes 183This specifies the number of inodes for the filesystem. 184If both 185.Fl i 186and 187.Fl n 188are specified then 189.Fl n 190takes precedence. 191.It Fl o 192Options are specified with a 193.Fl o 194flag followed by a comma separated string of options. 195See the 196.Xr mount 8 197man page for possible options and their meanings. 198.It Fl p Ar permissions 199This specifies the permissions of the root 200inode of the file system. 201.It Fl s Ar size 202The size of the file system in sectors. 203An 204.Sq s 205suffix will be interpreted as the number of sectors (the default). 206All other suffixes are interpreted as per other numeric arguments, 207except that the number is converted into sectors by dividing by the 208sector size (as specified by 209.Fl S Ar secsize ) 210after suffix interpretation. 211.It Fl u Ar username 212This specifies the user name or user id of the root 213inode of the file system. 214.El 215.Sh NOTES 216The owner and group ids of the root node of the new file system 217are set to the effective uid and gid of the user mounting 218the file system. 219.Sh EXAMPLES 220Mount a 32 MB mfs on /tmp: 221.Pp 222.Dl mount_mfs -s 32m swap /tmp 223.Sh SEE ALSO 224.Xr disktab 5 , 225.Xr fs 5 , 226.Xr disklabel 8 , 227.Xr diskpart 8 , 228.Xr dumpfs 8 , 229.\" .Xr format 8 , 230.Xr fsck_ffs 8 , 231.Xr fsirand 8 , 232.Xr mount 8 , 233.Xr newfs 8 , 234.Xr tunefs 8 235.Rs 236.%A M. McKusick 237.%A W. Joy 238.%A S. Leffler 239.%A R. Fabry 240.%T A Fast File System for UNIX , 241.%J ACM Transactions on Computer Systems 2 242.%V 3 243.%P pp 181-197 244.%D August 1984 245.%O (reprinted in the BSD System Manager's Manual) 246.Re 247.Sh HISTORY 248The 249.Nm 250command appeared in 251.Bx 4.2 . 252.Sh BUGS 253The 254.Cm async 255.Xr mount 8 256option is currently disabled in this file system because it causes 257hangs when writing lots of data. 258The problem is that MFS needs to allocate pages to clean pages, so if 259it waits until the last minute to clean pages then there may not be 260any of them available to do the cleaning. 261