[9fans] exportfs and import options: short guide with examples

[9fans] exportfs and import options: short guide with examples

[mycroftiv]

So, what's all this about exportfs/import, in brief?  It's easy to
understand with examples.  In all these examples, "listen" could be
either done with aux/listen and a service file or aux/listen1directly.

Default exportfs server with authentication (port 17007 standard):

	listen exportfs -a
	# authenticates clients, then lets them choose a subtree

Client mounts with:

	import server /remote/path /mount/point
	# import uses /remote/path to request a given sub-tree

exportfs server with no authentication

	listen exportfs

client mounts with:

	import -A server /remote/path /mount/point
	# the -A flag tells import to skip authentication

exportfs server with root selection

	listen exportfs -r /serve/this/path/only
	# exportfs now skips the tree request part of the protocol

client mounts with:

	srv tcp!server!port srvname /mount/point
	# no auth, no tree selection is a non-authed 9p server

exportfs server with authentication and root selection

	listen exportfs -a -r /serve/this/with/auth
	# exportfs now will auth clients, but skip tree negotiation

client mounts with:

	UNMOUNTABLE CURRENTLY
	# mc hammer says "cant touch this"

proposal:

	import -m cpu /mount/point
	# auths to server, skips tree request, and mounts successfully

This proposed additional option to import allows exportfs -a -r (and
exportfs -a -S which has the identical issue) to be useful as a
listener.  It has no affect on existing users and configurations.  If
this option isn't relevant to you, it can be completely ignored with
zero changes.  It allows those who wish to import and export using
this protocol variant (auth but no tree request) to do so with no
disruption to existing systems. The -B variant is also unaffected.

A patch(1) for this change has been submitted to sources.  The patch
used the -z flag, but apparently some existing users have this
modification already, and use the -m flag to import for "skip tree
request."

If this change is accepted, there is no change needed to any local
configuration, but users should be aware that some servers might begin
using this protocol variant, and know which flag is needed to connect
properly.

Ben Kidwell
"mycroftiv"

gridterm: ps |grep exportfs |wc -l
    306