1 .. SPDX-License-Identifier: GPL-2.0 2 3 ======================================= 4 v9fs: Plan 9 Resource Sharing for Linux 5 ======================================= 6 7 About 8 ===== 9 10 v9fs is a Unix implementation of the Plan 9 9p remote filesystem protocol. 11 12 This software was originally developed by Ron Minnich <rminnich@sandia.gov> 13 and 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 18 The best detailed explanation of the Linux implementation and applications of 19 the 9p client is available in the form of a USENIX paper: 20 21 https://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html 22 23 Other 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 36 Usage 37 ===== 38 39 For remote file server:: 40 41 mount -t 9p 10.10.1.2 /mnt/9 42 43 For 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 47 For server running on QEMU host with virtio transport:: 48 49 mount -t 9p -o trans=virtio <mount_tag> /mnt/9 50 51 where mount_tag is the tag associated by the server to each of the exported 52 mount points. Each 9P export is seen by the client as a virtio device with an 53 associated "mount_tag" property. Available mount tags can be 54 seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files. 55 56 Options 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 The mode can be specified as a bitmask or by using one of the 82 preexisting common 'shortcuts'. 83 The bitmask is described below: (unspecified bits are reserved) 84 85 ========== ==================================================== 86 0b00000000 all caches disabled, mmap disabled 87 0b00000001 file caches enabled 88 0b00000010 meta-data caches enabled 89 0b00000100 writeback behavior (as opposed to writethrough) 90 0b00001000 loose caches (no explicit consistency with server) 91 0b10000000 fscache enabled for persistent caching 92 ========== ==================================================== 93 94 The current shortcuts and their associated bitmask are: 95 96 ========= ==================================================== 97 none 0b00000000 (no caching) 98 readahead 0b00000001 (only read-ahead file caching) 99 mmap 0b00000101 (read-ahead + writeback file cache) 100 loose 0b00001111 (non-coherent file and meta-data caches) 101 fscache 0b10001111 (persistent loose cache) 102 ========= ==================================================== 103 104 NOTE: only these shortcuts are tested modes of operation at the 105 moment, so using other combinations of bit-patterns is not 106 known to work. Work on better cache support is in progress. 107 108 IMPORTANT: loose caches (and by extension at the moment fscache) 109 do not necessarily validate cached values on the server. In other 110 words changes on the server are not guaranteed to be reflected 111 on the client system. Only use this mode of operation if you 112 have an exclusive mount and the server will modify the filesystem 113 underneath you. 114 115 debug=n specifies debug level. The debug level is a bitmask. 116 117 ===== ================================ 118 0x01 display verbose error messages 119 0x02 developer debug (DEBUG_CURRENT) 120 0x04 display 9p trace 121 0x08 display VFS trace 122 0x10 display Marshalling debug 123 0x20 display RPC debug 124 0x40 display transport debug 125 0x80 display allocation debug 126 0x100 display protocol message debug 127 0x200 display Fid debug 128 0x400 display packet debug 129 0x800 display fscache tracing debug 130 ===== ================================ 131 132 rfdno=n the file descriptor for reading with trans=fd 133 134 wfdno=n the file descriptor for writing with trans=fd 135 136 msize=n the number of bytes to use for 9p packet payload 137 138 port=n port to connect to on the remote server 139 140 noextend force legacy mode (no 9p2000.u or 9p2000.L semantics) 141 142 version=name Select 9P protocol version. Valid options are: 143 144 ======== ============================== 145 9p2000 Legacy mode (same as noextend) 146 9p2000.u Use 9P2000.u protocol 147 9p2000.L Use 9P2000.L protocol 148 ======== ============================== 149 150 dfltuid attempt to mount as a particular uid 151 152 dfltgid attempt to mount with a particular gid 153 154 afid security channel - used by Plan 9 authentication protocols 155 156 nodevmap do not map special files - represent them as normal files. 157 This can be used to share devices/named pipes/sockets between 158 hosts. This functionality will be expanded in later versions. 159 160 directio bypass page cache on all read/write operations 161 162 ignoreqv ignore qid.version==0 as a marker to ignore cache 163 164 noxattr do not offer xattr functions on this mount. 165 166 access there are four access modes. 167 user 168 if a user tries to access a file on v9fs 169 filesystem for the first time, v9fs sends an 170 attach command (Tattach) for that user. 171 This is the default mode. 172 <uid> 173 allows only user with uid=<uid> to access 174 the files on the mounted filesystem 175 any 176 v9fs does single attach and performs all 177 operations as one user 178 clien 179 ACL based access check on the 9p client 180 side for access validation 181 182 cachetag cache tag to use the specified persistent cache. 183 cache tags for existing cache sessions can be listed at 184 /sys/fs/9p/caches. (applies only to cache=fscache) 185 ============= =============================================================== 186 187 Behavior 188 ======== 189 190 This section aims at describing 9p 'quirks' that can be different 191 from a local filesystem behaviors. 192 193 - Setting O_NONBLOCK on a file will make client reads return as early 194 as the server returns some data instead of trying to fill the read 195 buffer with the requested amount of bytes or end of file is reached. 196 197 Resources 198 ========= 199 200 Protocol specifications are maintained on github: 201 http://ericvh.github.com/9p-rfc/ 202 203 9p client and server implementations are listed on 204 http://9p.cat-v.org/implementations 205 206 A 9p2000.L server is being developed by LLNL and can be found 207 at http://code.google.com/p/diod/ 208 209 There are user and developer mailing lists available through the v9fs project 210 on sourceforge (http://sourceforge.net/projects/v9fs). 211 212 News and other information is maintained on a Wiki. 213 (http://sf.net/apps/mediawiki/v9fs/index.php). 214 215 Bug reports are best issued via the mailing list. 216 217 For more information on the Plan 9 Operating System check out 218 http://plan9.bell-labs.com/plan9 219 220 For information on Plan 9 from User Space (Plan 9 applications and libraries 221 ported to Linux/BSD/OSX/etc) check out https://9fans.github.io/plan9port/
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