src/kernel/linux/v4.14/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
	* VirtFS: A Virtualization Aware File System pass-through
		http://goo.gl/3WPDg

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.
                        none = default no cache policy, metadata and data
                                alike are synchronous.
			loose = no attempts are made at consistency,
                                intended for exclusive, read-only mounts
                        fscache = use FS-Cache for a persistent, read-only
				cache backend.
                        mmap = minimal cache that is only used for read-write
                                mmap.  Northing else is cached, like cache=none

  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

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

  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 four 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
			client = ACL based access check on the 9p client
			         side for access validation

  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
=========

Protocol specifications are maintained on github:
http://ericvh.github.com/9p-rfc/

9p client and server implementations are listed on
http://9p.cat-v.org/implementations

A 9p2000.L server is being developed by LLNL and can be found
at http://code.google.com/p/diod/

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

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

Bug reports are best issued via the mailing list.

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