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NetBSD 6.1.5 - man page for mount_tmpfs (netbsd section 8)

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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 absolute 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 maximum 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 indi-
     cate bytes (the default), a trailing 'k' to indicate 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 cre-
     ate 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
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