exportfs, srvfs – file server plumbing

exportfs [ –dsR ] [ –m msize ] [ –r root ] [ –P patternfile ] [ –S srvfile ]

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

Exportfs is a user level file server that allows Plan 9 cpu servers, rather than file servers, to export portions of a name space. It is usually started by other programs such as rcpu(1) after a secure channel has been established. 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:
d    Log all 9P traffic to standard error.
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
Serve the name space rooted at root.
S service
Serve 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)).
s    equivalent to –r /; kept for compatibility.
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.

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