DragonFly On-Line Manual Pages

TMPFS(5)                 DragonFly File Formats Manual                TMPFS(5)

NAME
     tmpfs -- efficient memory file system

SYNOPSIS
     To compile this driver into the kernel, place the following line in your
     kernel configuration file:

           options TMPFS

     Alternatively, to load the driver as a module at boot time, place the
     following line in loader.conf(5):

           tmpfs_load="YES"

OPTIONS
     The following options are available when mounting tmpfs file systems:

     gid     root group id.

     uid     root user id.

     mode    permissions in octal format.

     inodes  maximum number of inodes.

     size    maximum size for the file system.

     maxfilesize
             maximum file size of the file system.

DESCRIPTION
     In the DragonFly implementation, tmpfs filesystems are backed by swap
     space.  Only memory pressure will cause data to be backed to swap.  Nor-
     mal filesystem operations such as fsync(), buffer cache flushing, and
     vnode recycling have no effect.

     tmpfs stores meta-data in wired kernel memory.  Meta-data is not backed
     by swap so care must be taken if using tmpfs to store large numbers of
     small files.

     It is recommended that a large amount of swap space be reserved on modern
     DragonFly platforms to accommodate tmpfs and other subsystems.  32-bit
     kernels can accommodate 32G of swap by default while 64-bit kernels can
     accommodate 512G of swap by default.  These defaults can be increased
     though it should be noted that 32-bit kernels are ultimately limited by
     the amount of KVM available in its small 32-bit address space.

     tmpfs will allocate and deallocate swap backing store on the fly based on
     usage.  By default tmpfs allows up to 100% of swap space to be used.  If
     this is not desirable then the size option should be used to limit its
     size.

     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
     To mount a tmpfs memory file system:

           mount -t tmpfs tmpfs /tmp

SEE ALSO
     fstab(5), mount_nfs(8), mount_tmpfs(8), swapcache(8)

HISTORY
     The tmpfs driver first appeared in DragonFly 2.5.

AUTHORS
     The tmpfs kernel implementation was written by Julio M. Merino Vidal
     <jmmv@NetBSD.org> as a Google SoC project.

     Rohit Jalan and others ported it from NetBSD to FreeBSD.

     Naoya Sugioka and others ported it from NetBSD to DragonFly.

     This manual page was written by Xin LI <delphij@FreeBSD.org>.

BUGS
     To mount NFS exported tmpfs DragonFly NFS client need to disable Read-
     dirPlus, see mount_nfs(8).

DragonFly 3.5                  February 2, 2010                  DragonFly 3.5