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