exportfs, srvfs – network file server plumbing

exportfs [ options ]

srvfs [ –dR ] [ –p perm ] [ –P patternfile ] [ –e exportprog ] name path

Exportfs is a user level file server that allows Plan 9 compute servers, rather than file servers, to export portions of a name space across networks. The service is started either by the cpu(1) command or by a network listener process. An initial protocol establishes a root directory for the exported name space, optional use of aan(8), and type of encryption: clear (none), ssl (SSLv2), or tls. The connection to exportfs is then mounted, typically on /mnt/term. Exportfs then acts as a relay file server: operations in the imported file tree are executed on the remote server and the results returned. This gives the appearance of exporting a name space from a remote machine into a local file tree.

The options are:
A addressUse the network address to announce aan(8) connections, if requested by the initial protocol.
a        Authenticate the user with the p9any protocol before running the regular exportfs session; used when exportfs is invoked to handle an incoming network connection. Exportfs creates a new name space for each connection, using /lib/namespace by default (see namespace(6)). –B addressDial address, authenticate as a p9any client, and then serve that network connection. Requires setting the root of the name space with –r or –s. The remote system should run import –B to handle the call. See import(4) for an example.
d –f dbgfile
Log all 9P traffic to dbgfile (default /tmp/exportdb).
e 'enc auth'
Set the encryption and authentication algorithms to use for encrypting the wire traffic (see ssl(3)) if using SSLv2. The defaults are rc4_256 and sha1.
m msize   Set the maximum message size that exportfs should offer to send (see version(5)); this helps tunneled 9P connections to avoid unnecessary fragmentation.
N nsfile   Serve the name space described by nsfile.
n        Disallow mounts by user none.
P patternfile
Restrict the set of exported files. Patternfile contains one regular expression per line, to be matched against path names relative to the current working directory and starting with ./. For a file to be exported, all lines with a prefix + must match and all those with prefix – must not match. –
R        Make the served name space read only.
r root    Bypass the initial protocol, serving the name space rooted at root. A corresponding import(4) must use the –m option.
S service   Bypass the initial protocol, serving the result of mounting service. A separate mount is used for each attach(5) message, to correctly handle servers in which each mount corresponds to a different client (e.g., rio(4)). A corresponding import(4) must use the –m option.
s        equivalent to –r /; kept for compatibility.

The cpu command uses exportfs to serve device files in the terminal. The import(4) command calls exportfs on a remote machine, permitting users to access arbitrary pieces of name space on other systems.

Because the kernel disallows reads and writes on mounted pipes (as might be found in /srv), exportfs calls itself (with appropriate –m and –S options) to simulate reads and writes on such files.

Srvfs invokes exportprog (default /bin/exportfs) to create a mountable file system from a name space and posts it at /srv/name, which is created with mode perm (default 0600). The name space is the directory tree rooted at path. The –d, –P, and –R options, if present, are relayed to exportprog.

To export the archive of one user for one month, except for secrets,
cd /n/dump
echo '+ ^\.(/2003(/10..(/usr(/glenda/?)?)?)?)?' > /tmp/pattern
echo '– \.(aes|pgp)$' >> /tmp/pattern
exportfs –P /tmp/pattern

Use srvfs to enable mounting of an FTP file system (see ftpfs(4)) in several windows, or to publish a /proc (see proc(3)) with a broken process so a remote person may debug the program:
srvfs ftp /n/ftp
srvfs broke /mnt/term/proc

Use srvfs to obtain a copy of a service to be manipulated directly by a user program like nfsserver(8):
srvfs nfs.boot /srv/boot
aux/nfsserver –f /srv/nfs.boot

Use srvfs to spy on all accesses to a particular subtree:
srvfs –d spy /
tail –f /tmp/exportdb &
mount /srv/spy /n/spy
cd /n/spy; ls


dial(2), tls(3), import(4), aan(8), listen(8)

SSLv2 and RC4 are deprecated.
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