1.. SPDX-License-Identifier: GPL-2.0
2
3=======================================
4v9fs: Plan 9 Resource Sharing for Linux
5=======================================
6
7About
8=====
9
10v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol.
11
12This software was originally developed by Ron Minnich <rminnich@sandia.gov>
13and Maya Gokhale.  Additional development by Greg Watson
14<gwatson@lanl.gov> and most recently Eric Van Hensbergen
15<ericvh@gmail.com>, Latchesar Ionkov <lucho@ionkov.net> and Russ Cox
16<rsc@swtch.com>.
17
18The best detailed explanation of the Linux implementation and applications of
19the 9p client is available in the form of a USENIX paper:
20
21   https://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html
22
23Other applications are described in the following papers:
24
25	* XCPU & Clustering
26	  http://xcpu.org/papers/xcpu-talk.pdf
27	* KVMFS: control file system for KVM
28	  http://xcpu.org/papers/kvmfs.pdf
29	* CellFS: A New Programming Model for the Cell BE
30	  http://xcpu.org/papers/cellfs-talk.pdf
31	* PROSE I/O: Using 9p to enable Application Partitions
32	  http://plan9.escet.urjc.es/iwp9/cready/PROSE_iwp9_2006.pdf
33	* VirtFS: A Virtualization Aware File System pass-through
34	  http://goo.gl/3WPDg
35
36Usage
37=====
38
39For remote file server::
40
41	mount -t 9p 10.10.1.2 /mnt/9
42
43For Plan 9 From User Space applications (http://swtch.com/plan9)::
44
45	mount -t 9p `namespace`/acme /mnt/9 -o trans=unix,uname=$USER
46
47For server running on QEMU host with virtio transport::
48
49	mount -t 9p -o trans=virtio <mount_tag> /mnt/9
50
51where mount_tag is the tag associated by the server to each of the exported
52mount points. Each 9P export is seen by the client as a virtio device with an
53associated "mount_tag" property. Available mount tags can be
54seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files.
55
56Options
57=======
58
59  ============= ===============================================================
60  trans=name	select an alternative transport.  Valid options are
61  		currently:
62
63			========  ============================================
64			unix 	  specifying a named pipe mount point
65			tcp	  specifying a normal TCP/IP connection
66			fd   	  used passed file descriptors for connection
67                                  (see rfdno and wfdno)
68			virtio	  connect to the next virtio channel available
69				  (from QEMU with trans_virtio module)
70			rdma	  connect to a specified RDMA channel
71			========  ============================================
72
73  uname=name	user name to attempt mount as on the remote server.  The
74  		server may override or ignore this value.  Certain user
75		names may require authentication.
76
77  aname=name	aname specifies the file tree to access when the server is
78  		offering several exported file systems.
79
80  cache=mode	specifies a caching policy.  By default, no caches are used.
81
82                        none
83				default no cache policy, metadata and data
84                                alike are synchronous.
85			loose
86				no attempts are made at consistency,
87                                intended for exclusive, read-only mounts
88                        fscache
89				use FS-Cache for a persistent, read-only
90				cache backend.
91                        mmap
92				minimal cache that is only used for read-write
93                                mmap.  Northing else is cached, like cache=none
94
95  debug=n	specifies debug level.  The debug level is a bitmask.
96
97			=====   ================================
98			0x01    display verbose error messages
99			0x02    developer debug (DEBUG_CURRENT)
100			0x04    display 9p trace
101			0x08    display VFS trace
102			0x10    display Marshalling debug
103			0x20    display RPC debug
104			0x40    display transport debug
105			0x80    display allocation debug
106			0x100   display protocol message debug
107			0x200   display Fid debug
108			0x400   display packet debug
109			0x800   display fscache tracing debug
110			=====   ================================
111
112  rfdno=n	the file descriptor for reading with trans=fd
113
114  wfdno=n	the file descriptor for writing with trans=fd
115
116  msize=n	the number of bytes to use for 9p packet payload
117
118  port=n	port to connect to on the remote server
119
120  noextend	force legacy mode (no 9p2000.u or 9p2000.L semantics)
121
122  version=name	Select 9P protocol version. Valid options are:
123
124			========        ==============================
125			9p2000          Legacy mode (same as noextend)
126			9p2000.u        Use 9P2000.u protocol
127			9p2000.L        Use 9P2000.L protocol
128			========        ==============================
129
130  dfltuid	attempt to mount as a particular uid
131
132  dfltgid	attempt to mount with a particular gid
133
134  afid		security channel - used by Plan 9 authentication protocols
135
136  nodevmap	do not map special files - represent them as normal files.
137  		This can be used to share devices/named pipes/sockets between
138		hosts.  This functionality will be expanded in later versions.
139
140  access	there are four access modes.
141			user
142				if a user tries to access a file on v9fs
143			        filesystem for the first time, v9fs sends an
144			        attach command (Tattach) for that user.
145				This is the default mode.
146			<uid>
147				allows only user with uid=<uid> to access
148				the files on the mounted filesystem
149			any
150				v9fs does single attach and performs all
151				operations as one user
152			clien
153				 ACL based access check on the 9p client
154			         side for access validation
155
156  cachetag	cache tag to use the specified persistent cache.
157		cache tags for existing cache sessions can be listed at
158		/sys/fs/9p/caches. (applies only to cache=fscache)
159  ============= ===============================================================
160
161Behavior
162========
163
164This section aims at describing 9p 'quirks' that can be different
165from a local filesystem behaviors.
166
167 - Setting O_NONBLOCK on a file will make client reads return as early
168   as the server returns some data instead of trying to fill the read
169   buffer with the requested amount of bytes or end of file is reached.
170
171Resources
172=========
173
174Protocol specifications are maintained on github:
175http://ericvh.github.com/9p-rfc/
176
1779p client and server implementations are listed on
178http://9p.cat-v.org/implementations
179
180A 9p2000.L server is being developed by LLNL and can be found
181at http://code.google.com/p/diod/
182
183There are user and developer mailing lists available through the v9fs project
184on sourceforge (http://sourceforge.net/projects/v9fs).
185
186News and other information is maintained on a Wiki.
187(http://sf.net/apps/mediawiki/v9fs/index.php).
188
189Bug reports are best issued via the mailing list.
190
191For more information on the Plan 9 Operating System check out
192http://plan9.bell-labs.com/plan9
193
194For information on Plan 9 from User Space (Plan 9 applications and libraries
195ported to Linux/BSD/OSX/etc) check out https://9fans.github.io/plan9port/
196