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Annotation of src/sbin/mount_tmpfs/mount_tmpfs.8, Revision 1.12.6.1

1.12.6.1! mjf         1: .\"    $NetBSD: mount_tmpfs.8,v 1.13 2008/02/13 14:21:57 rillig Exp $
1.1       jmmv        2: .\"
1.9       jmmv        3: .\" Copyright (c) 2005, 2006 The NetBSD Foundation, Inc.
1.1       jmmv        4: .\" All rights reserved.
                      5: .\"
                      6: .\" This code is derived from software contributed to The NetBSD Foundation
1.3       jmmv        7: .\" by Julio M. Merino Vidal, developed as part of Google's Summer of Code
                      8: .\" 2005 program.
1.1       jmmv        9: .\"
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1.12.6.1! mjf        38: .Dd February 13, 2008
1.1       jmmv       39: .Dt MOUNT_TMPFS 8
                     40: .Os
                     41: .Sh NAME
                     42: .Nm mount_tmpfs
                     43: .Nd mount an efficient memory file system
                     44: .Sh SYNOPSIS
                     45: .Nm
                     46: .Op Fl g Ar group
                     47: .Op Fl m Ar mode
                     48: .Op Fl n Ar nodes
                     49: .Op Fl o Ar options
                     50: .Op Fl s Ar size
                     51: .Op Fl u Ar user
                     52: .Ar tmpfs
                     53: .Ar mount_point
                     54: .Sh DESCRIPTION
                     55: The
                     56: .Nm
                     57: command attaches an instance of the efficient memory file system to the
                     58: global file system namespace.
1.12.6.1! mjf        59: The
        !            60: .Ar tmpfs
        !            61: parameter only exists for compatibility with the other mount commands and
        !            62: is ignored.
1.1       jmmv       63: The directory specified by
                     64: .Ar mount_point
1.4       jmmv       65: is converted to an absolute path before use and its attributes (owner,
                     66: group and mode) are inherited unless explicitly overriden by the options
                     67: described below.
1.1       jmmv       68: .Pp
                     69: The following options are supported:
                     70: .Bl -tag -width XoXoptions
                     71: .It Fl g Ar group
                     72: Specifies the group name or GID of the root inode of the file system.
1.4       jmmv       73: Defaults to the mount point's GID.
1.1       jmmv       74: .It Fl m Ar mode
                     75: Specifies the mode (in octal notation) of the root inode of the file system.
1.4       jmmv       76: Defaults to the mount point's mode.
1.1       jmmv       77: .It Fl n Ar nodes
1.2       jmmv       78: Specifies the maximum number of nodes available to the file system.
1.10      jmmv       79: If not specified, the file system chooses a reasonable maximum given its
                     80: size at mount time, which can be limited with
                     81: .Fl s .
1.1       jmmv       82: .It Fl o Ar options
                     83: Options are specified with a
                     84: .Fl o
                     85: flag followed by a comma-separated string of options.
                     86: See the
                     87: .Xr mount 8
                     88: man page for possible options and their meanings.
                     89: .It Fl s Ar size
                     90: Specifies the total file system size in bytes.
                     91: If zero is given (the default), the available amount of memory (including
                     92: main memory and swap space) will be used.
                     93: Note that four megabytes are always reserved for the system and cannot
1.2       jmmv       94: be assigned to the file system.
1.1       jmmv       95: .It Fl u Ar user
                     96: Specifies the user name or UID of the root inode of the file system.
1.4       jmmv       97: Defaults to the mount point's UID.
1.1       jmmv       98: .El
                     99: .Pp
                    100: Every option that accepts a numerical value as its argument can take a
                    101: trailing
                    102: .Sq b
                    103: to indicate bytes (the default), a trailing
                    104: .Sq k
                    105: to indicate kilobytes, a trailing
                    106: .Sq M
                    107: to indicate megabytes or a trailing
                    108: .Sq G
                    109: to indicate gigabytes.
1.5       jmmv      110: Note that both lowercase and uppercase forms of these letters are allowed.
1.7       jmmv      111: .Sh EXAMPLES
                    112: The following command mounts a tmpfs instance over the
                    113: .Pa /tmp
                    114: directory, inheriting its owner, group and mode settings:
                    115: .Pp
                    116: .Ic "mount -t tmpfs tmpfs /tmp"
                    117: .Pp
                    118: The following command mounts a tmpfs instance over the
                    119: .Pa /mnt
                    120: directory, setting a 20 megabytes limit in space, owned by the
                    121: .Sq joe
                    122: user and belonging to the
                    123: .Sq users
                    124: group, with a restricted 0700 mode:
                    125: .Pp
                    126: .Ic "mount -t tmpfs -o -s20M -o -ujoe -o -gusers -o -m0700 tmpfs /mnt"
1.8       jmmv      127: .Pp
                    128: See
                    129: .Pa /usr/share/examples/fstab/fstab.ramdisk
                    130: for some examples on how to add tmpfs entries to
                    131: .Pa /etc/fstab .
1.1       jmmv      132: .Sh SEE ALSO
                    133: .Xr fstab 5 ,
1.6       jmmv      134: .Xr mount 8
1.1       jmmv      135: .Sh HISTORY
                    136: The
                    137: .Nm
                    138: utility first appeared in
                    139: .Nx 4.0 .
1.10      jmmv      140: .Sh BUGS
                    141: File system meta-data is not pageable.
                    142: If there is not enough main memory to hold this information, the system may
                    143: become unstable or very unresponsive because it will not be able to allocate
                    144: required memory.
1.12      jmmv      145: A malicious user could trigger this condition if he could create lots of
1.10      jmmv      146: files inside a size-unbounded tmpfs file system.
                    147: Limiting the number of nodes per file system
1.11      wiz       148: .Pq Fl n
1.10      jmmv      149: will prevent this; the default value for this setting is also often adjusted
                    150: to an adequate value to resolve this.