netbsd man page for mount_tmpfs

MOUNT_TMPFS(8)						    BSD System Manager's Manual 					    MOUNT_TMPFS(8)

NAME
     mount_tmpfs -- mount an efficient memory file system

SYNOPSIS
     mount_tmpfs [-g group] [-m mode] [-n nodes] [-o options] [-s size] [-u user] tmpfs mount_point

DESCRIPTION
     The mount_tmpfs command attaches an instance of the efficient memory file system to the global file system namespace.  The tmpfs parameter
     only exists for compatibility with the other mount commands and is ignored.  The directory specified by mount_point is converted to an abso-
     lute path before use and its attributes (owner, group and mode) are inherited unless explicitly overriden by the options described below.

     The following options are supported:

     -g group	 Specifies the group name or GID of the root inode of the file system.	Defaults to the mount point's GID.

     -m mode	 Specifies the mode (in octal notation) of the root inode of the file system.  Defaults to the mount point's mode.

     -n nodes	 Specifies the maximum number of nodes available to the file system.  If not specified, the file system chooses a reasonable maxi-
		 mum given its size at mount time, which can be limited with -s.

     -o options  Options are specified with a -o flag followed by a comma-separated string of options.	See the mount(8) man page for possible
		 options and their meanings.

     -s size	 Specifies the total file system size in bytes.  If zero is given (the default), the available amount of memory (including main
		 memory and swap space) will be used.  Note that four megabytes are always reserved for the system and cannot be assigned to the
		 file system.

     -u user	 Specifies the user name or UID of the root inode of the file system.  Defaults to the mount point's UID.

     Every option that accepts a numerical value as its argument can take a trailing 'b' to indicate bytes (the default), a trailing 'k' to indi-
     cate kilobytes, a trailing 'M' to indicate megabytes or a trailing 'G' to indicate gigabytes.  Note that both lowercase and uppercase forms
     of these letters are allowed.

EXAMPLES
     The following command mounts a tmpfs instance over the /tmp directory, inheriting its owner, group and mode settings:

     mount -t tmpfs tmpfs /tmp

     The following command mounts a tmpfs instance over the /mnt directory, setting a 20 megabytes limit in space, owned by the 'joe' user and
     belonging to the 'users' group, with a restricted 0700 mode:

     mount -t tmpfs -o -s20M -o -ujoe -o -gusers -o -m0700 tmpfs /mnt

     See /usr/share/examples/fstab/fstab.ramdisk for some examples on how to add tmpfs entries to /etc/fstab.

SEE ALSO
     fstab(5), mount(8)

HISTORY
     The mount_tmpfs utility first appeared in NetBSD 4.0.

BUGS
     File system meta-data is not pageable.  If there is not enough main memory to hold this information, the system may become unstable or very
     unresponsive because it will not be able to allocate required memory.  A malicious user could trigger this condition if he could create lots
     of files inside a size-unbounded tmpfs file system.  Limiting the number of nodes per file system (-n) will prevent this; the default value
     for this setting is also often adjusted to an adequate value to resolve this.

BSD
								 February 13, 2008							       BSD