NAME
mount_tmpfs —
mount an efficient memory file
system
SYNOPSIS
mount_tmpfs |
[-C] [-f
maxfilesize] [-g
group] [-m
mode] [-n
nodes] [-o
options] [-s
size] [-u
user] tmpfs
mount_point |
DESCRIPTION
Themount_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
overridden by the options described below.
The following options are supported:
-C- Tells
mount_tmpfsto copy the underlying file system into the tmpfs mount being created over it. -fmaxfilesize- Specifies the maximum file size of the file system.
-ggroup- Specifies the group name or GID of the root inode of the file system. Defaults to the mount point's GID.
-mmode- Specifies the mode (in octal notation) of the root inode of the file system. Defaults to the mount point's mode.
-nnodes- 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. -ooptions- Options are specified with a
-oflag followed by a comma-separated string of options. See the mount(8) and tmpfs(5) man page for possible options and their meanings. -ssize- Specifies the total file system size. 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.
-uuser- 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 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
or
mount -t tmpfs -o
size=20M,uid=joe,gid=users,mode=0700 tmpfs /mnt
SEE ALSO
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.