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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/