Documentation/filesystems/9p.txt

	  	    v9fs: Plan 9 Resource Sharing for Linux
		    =======================================

ABOUT
=====

v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol.

This software was originally developed by Ron Minnich <rminnich@sandia.gov>
and Maya Gokhale.  Additional development by Greg Watson
<gwatson@lanl.gov> and most recently Eric Van Hensbergen
<ericvh@gmail.com>, Latchesar Ionkov <lucho@ionkov.net> and Russ Cox
<rsc@swtch.com>.

The best detailed explanation of the Linux implementation and applications of
the 9p client is available in the form of a USENIX paper:
   http://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html

Other applications are described in the following papers:
	* XCPU & Clustering
		http://xcpu.org/papers/xcpu-talk.pdf
	* KVMFS: control file system for KVM
		http://xcpu.org/papers/kvmfs.pdf
	* CellFS: A New Programming Model for the Cell BE
		http://xcpu.org/papers/cellfs-talk.pdf
	* PROSE I/O: Using 9p to enable Application Partitions
		http://plan9.escet.urjc.es/iwp9/cready/PROSE_iwp9_2006.pdf

USAGE
=====

For remote file server:

	mount -t 9p 10.10.1.2 /mnt/9

For Plan 9 From User Space applications (http://swtch.com/plan9)

	mount -t 9p `namespace`/acme /mnt/9 -o trans=unix,uname=$USER

For server running on QEMU host with virtio transport:

	mount -t 9p -o trans=virtio <mount_tag> /mnt/9

where mount_tag is the tag associated by the server to each of the exported
mount points. Each 9P export is seen by the client as a virtio device with an
associated "mount_tag" property. Available mount tags can be
seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files.

OPTIONS
=======

  trans=name	select an alternative transport.  Valid options are
  		currently:
			unix 	- specifying a named pipe mount point
			tcp	- specifying a normal TCP/IP connection
			fd   	- used passed file descriptors for connection
                                (see rfdno and wfdno)
			virtio	- connect to the next virtio channel available
				(from QEMU with trans_virtio module)
			rdma	- connect to a specified RDMA channel

  uname=name	user name to attempt mount as on the remote server.  The
  		server may override or ignore this value.  Certain user
		names may require authentication.

  aname=name	aname specifies the file tree to access when the server is
  		offering several exported file systems.

  cache=mode	specifies a caching policy.  By default, no caches are used.
			loose = no attempts are made at consistency,
                                intended for exclusive, read-only mounts
			fscache = use FS-Cache for a persistent, read-only
				cache backend.

  debug=n	specifies debug level.  The debug level is a bitmask.
			0x01  = display verbose error messages
			0x02  = developer debug (DEBUG_CURRENT)
			0x04  = display 9p trace
			0x08  = display VFS trace
			0x10  = display Marshalling debug
			0x20  = display RPC debug
			0x40  = display transport debug
			0x80  = display allocation debug
			0x100 = display protocol message debug
			0x200 = display Fid debug
			0x400 = display packet debug
			0x800 = display fscache tracing debug

  rfdno=n	the file descriptor for reading with trans=fd

  wfdno=n	the file descriptor for writing with trans=fd

  maxdata=n	the number of bytes to use for 9p packet payload (msize)

  port=n	port to connect to on the remote server

  noextend	force legacy mode (no 9p2000.u or 9p2000.L semantics)

  version=name	Select 9P protocol version. Valid options are:
			9p2000          - Legacy mode (same as noextend)
			9p2000.u        - Use 9P2000.u protocol
			9p2000.L        - Use 9P2000.L protocol

  dfltuid	attempt to mount as a particular uid

  dfltgid	attempt to mount with a particular gid

  afid		security channel - used by Plan 9 authentication protocols

  nodevmap	do not map special files - represent them as normal files.
  		This can be used to share devices/named pipes/sockets between
		hosts.  This functionality will be expanded in later versions.

  access	there are three access modes.
			user  = if a user tries to access a file on v9fs
			        filesystem for the first time, v9fs sends an
			        attach command (Tattach) for that user.
				This is the default mode.
			<uid> = allows only user with uid=<uid> to access
				the files on the mounted filesystem
			any   = v9fs does single attach and performs all
				operations as one user

  cachetag	cache tag to use the specified persistent cache.
		cache tags for existing cache sessions can be listed at
		/sys/fs/9p/caches. (applies only to cache=fscache)

RESOURCES
=========

Our current recommendation is to use Inferno (http://www.vitanuova.com/nferno/index.html)
as the 9p server.  You can start a 9p server under Inferno by issuing the
following command:
   ; styxlisten -A tcp!*!564 export '#U*'

The -A specifies an unauthenticated export.  The 564 is the port # (you may
have to choose a higher port number if running as a normal user).  The '#U*'
specifies exporting the root of the Linux name space.  You may specify a
subset of the namespace by extending the path: '#U*'/tmp would just export
/tmp.  For more information, see the Inferno manual pages covering styxlisten
and export.

A Linux version of the 9p server is now maintained under the npfs project
on sourceforge (http://sourceforge.net/projects/npfs).  The currently
maintained version is the single-threaded version of the server (named spfs)
available from the same SVN repository.

There are user and developer mailing lists available through the v9fs project
on sourceforge (http://sourceforge.net/projects/v9fs).

A stand-alone version of the module (which should build for any 2.6 kernel)
is available via (http://github.com/ericvh/9p-sac/tree/master)

News and other information is maintained on SWiK (http://swik.net/v9fs)
and the Wiki (http://sf.net/apps/mediawiki/v9fs/index.php).

Bug reports may be issued through the kernel.org bugzilla 
(http://bugzilla.kernel.org)

For more information on the Plan 9 Operating System check out
http://plan9.bell-labs.com/plan9

For information on Plan 9 from User Space (Plan 9 applications and libraries
ported to Linux/BSD/OSX/etc) check out http://swtch.com/plan9


STATUS
======

The 2.6 kernel support is working on PPC and x86.

PLEASE USE THE KERNEL BUGZILLA TO REPORT PROBLEMS. (http://bugzilla.kernel.org)