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195 lines
6.6 KiB
195 lines
6.6 KiB
.. SPDX-License-Identifier: GPL-2.0 |
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======================================= |
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v9fs: Plan 9 Resource Sharing for Linux |
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======================================= |
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About |
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===== |
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v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol. |
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This software was originally developed by Ron Minnich <[email protected]> |
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and Maya Gokhale. Additional development by Greg Watson |
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<[email protected]> and most recently Eric Van Hensbergen |
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<[email protected]>, Latchesar Ionkov <[email protected]> and Russ Cox |
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<[email protected]>. |
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The best detailed explanation of the Linux implementation and applications of |
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the 9p client is available in the form of a USENIX paper: |
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https://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html |
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Other applications are described in the following papers: |
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* XCPU & Clustering |
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http://xcpu.org/papers/xcpu-talk.pdf |
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* KVMFS: control file system for KVM |
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http://xcpu.org/papers/kvmfs.pdf |
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* CellFS: A New Programming Model for the Cell BE |
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http://xcpu.org/papers/cellfs-talk.pdf |
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* PROSE I/O: Using 9p to enable Application Partitions |
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http://plan9.escet.urjc.es/iwp9/cready/PROSE_iwp9_2006.pdf |
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* VirtFS: A Virtualization Aware File System pass-through |
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http://goo.gl/3WPDg |
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Usage |
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For remote file server:: |
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mount -t 9p 10.10.1.2 /mnt/9 |
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For Plan 9 From User Space applications (http://swtch.com/plan9):: |
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mount -t 9p `namespace`/acme /mnt/9 -o trans=unix,uname=$USER |
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For server running on QEMU host with virtio transport:: |
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mount -t 9p -o trans=virtio <mount_tag> /mnt/9 |
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where mount_tag is the tag associated by the server to each of the exported |
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mount points. Each 9P export is seen by the client as a virtio device with an |
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associated "mount_tag" property. Available mount tags can be |
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seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files. |
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Options |
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======= |
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============= =============================================================== |
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trans=name select an alternative transport. Valid options are |
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currently: |
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======== ============================================ |
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unix specifying a named pipe mount point |
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tcp specifying a normal TCP/IP connection |
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fd used passed file descriptors for connection |
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(see rfdno and wfdno) |
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virtio connect to the next virtio channel available |
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(from QEMU with trans_virtio module) |
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rdma connect to a specified RDMA channel |
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======== ============================================ |
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uname=name user name to attempt mount as on the remote server. The |
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server may override or ignore this value. Certain user |
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names may require authentication. |
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aname=name aname specifies the file tree to access when the server is |
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offering several exported file systems. |
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cache=mode specifies a caching policy. By default, no caches are used. |
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none |
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default no cache policy, metadata and data |
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alike are synchronous. |
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loose |
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no attempts are made at consistency, |
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intended for exclusive, read-only mounts |
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fscache |
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use FS-Cache for a persistent, read-only |
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cache backend. |
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mmap |
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minimal cache that is only used for read-write |
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mmap. Northing else is cached, like cache=none |
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debug=n specifies debug level. The debug level is a bitmask. |
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===== ================================ |
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0x01 display verbose error messages |
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0x02 developer debug (DEBUG_CURRENT) |
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0x04 display 9p trace |
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0x08 display VFS trace |
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0x10 display Marshalling debug |
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0x20 display RPC debug |
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0x40 display transport debug |
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0x80 display allocation debug |
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0x100 display protocol message debug |
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0x200 display Fid debug |
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0x400 display packet debug |
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0x800 display fscache tracing debug |
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===== ================================ |
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rfdno=n the file descriptor for reading with trans=fd |
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wfdno=n the file descriptor for writing with trans=fd |
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msize=n the number of bytes to use for 9p packet payload |
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port=n port to connect to on the remote server |
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noextend force legacy mode (no 9p2000.u or 9p2000.L semantics) |
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version=name Select 9P protocol version. Valid options are: |
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======== ============================== |
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9p2000 Legacy mode (same as noextend) |
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9p2000.u Use 9P2000.u protocol |
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9p2000.L Use 9P2000.L protocol |
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======== ============================== |
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dfltuid attempt to mount as a particular uid |
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dfltgid attempt to mount with a particular gid |
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afid security channel - used by Plan 9 authentication protocols |
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nodevmap do not map special files - represent them as normal files. |
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This can be used to share devices/named pipes/sockets between |
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hosts. This functionality will be expanded in later versions. |
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access there are four access modes. |
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user |
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if a user tries to access a file on v9fs |
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filesystem for the first time, v9fs sends an |
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attach command (Tattach) for that user. |
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This is the default mode. |
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<uid> |
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allows only user with uid=<uid> to access |
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the files on the mounted filesystem |
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any |
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v9fs does single attach and performs all |
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operations as one user |
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clien |
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ACL based access check on the 9p client |
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side for access validation |
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cachetag cache tag to use the specified persistent cache. |
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cache tags for existing cache sessions can be listed at |
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/sys/fs/9p/caches. (applies only to cache=fscache) |
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============= =============================================================== |
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Behavior |
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======== |
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This section aims at describing 9p 'quirks' that can be different |
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from a local filesystem behaviors. |
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- Setting O_NONBLOCK on a file will make client reads return as early |
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as the server returns some data instead of trying to fill the read |
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buffer with the requested amount of bytes or end of file is reached. |
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Resources |
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========= |
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Protocol specifications are maintained on github: |
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http://ericvh.github.com/9p-rfc/ |
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9p client and server implementations are listed on |
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http://9p.cat-v.org/implementations |
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A 9p2000.L server is being developed by LLNL and can be found |
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at http://code.google.com/p/diod/ |
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There are user and developer mailing lists available through the v9fs project |
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on sourceforge (http://sourceforge.net/projects/v9fs). |
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News and other information is maintained on a Wiki. |
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(http://sf.net/apps/mediawiki/v9fs/index.php). |
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Bug reports are best issued via the mailing list. |
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For more information on the Plan 9 Operating System check out |
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http://plan9.bell-labs.com/plan9 |
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For information on Plan 9 from User Space (Plan 9 applications and libraries |
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ported to Linux/BSD/OSX/etc) check out https://9fans.github.io/plan9port/
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