MOUNT_MFS(8)            NetBSD System Manager's Manual            MOUNT_MFS(8)

     mount_mfs - mount a memory based file system

     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

     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)
           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-

     -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

     -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.

     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.

     Mount a 32 MB mfs on /tmp:

           mount_mfs -s 32m swap /tmp

     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).

     The mount_mfs command appeared in 4.2BSD.

NetBSD 1.6                       May 21, 2002                                3

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