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v9fs: Plan 9 Resource Sharing for Linux
v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol.
This software was originally developed by Ron Minnich <>
and Maya Gokhale. Additional development by Greg Watson
<> and most recently Eric Van Hensbergen
<>, Latchesar Ionkov <> and Russ Cox
The best detailed explanation of the Linux implementation and applications of
the 9p client is available in the form of a USENIX paper:
Other applications are described in the following papers:
* XCPU & Clustering
* KVMFS: control file system for KVM
* CellFS: A New Programming Model for the Cell BE
* PROSE I/O: Using 9p to enable Application Partitions
For remote file server:
mount -t 9p /mnt/9
For Plan 9 From User Space applications (
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.
trans=name select an alternative transport. Valid options are
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)
Our current recommendation is to use Inferno (
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 ( 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 (
A stand-alone version of the module (which should build for any 2.6 kernel)
is available via (
News and other information is maintained on SWiK (
and the Wiki (
Bug reports may be issued through the bugzilla
For more information on the Plan 9 Operating System check out
For information on Plan 9 from User Space (Plan 9 applications and libraries
ported to Linux/BSD/OSX/etc) check out
The 2.6 kernel support is working on PPC and x86.