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.TH U9FS 4

.SH NAME

u9fs \- serve 9P from Unix

.SH SYNOPSIS

.B u9fs

[

.B -Dnz

]

[

.B -a

.I authtype

]

[

.B -A

.I autharg

]

[

.B -l

.I logfile

]

[

.B -m

.I msize

]

[

.B -u

.I onlyuser

]

.I fsroot

.SH DESCRIPTION

.I U9fs

is

.I not

a Plan 9 program.  Instead it is a program that

serves Unix files to Plan 9 machines using the 9P protocol

(see

.IR intro (5)).

It is typically invoked on a

Unix machine by

.B inetd

with its standard input and output connected to a

network connection, typically TCP on an Ethernet.

It typically runs as user

.B root

and multiplexes access to multiple Plan 9 clients over the single wire.

It assumes Plan 9 uids match Unix login names,

and changes to the corresponding Unix effective uid when processing requests.

Characters in file and directory names unacceptable to Plan 9 are translated

into a three-character sequence:

.L \e

followed by two hexadecimal digits.

.I U9fs

serves both 9P1 (the 9P protocol as used by

the second and third editions of Plan 9) and 9P2000.

.PP

The options are:

.TF "\fL-A \fIautharg"

.PD

.TP

.B -D

Write very chatty debugging output to the log file (see

.B -l

option below).

.TP

.B -n

Signals that

.I u9fs

is

.I not

being invoked with a network connection

on standard input and output, and thus should

not try to determine the remote address of the connection.

This is useful when

.I u9fs

is not invoked from

.I inetd

(see examples below).

.TP

.B -z

Truncate the log file on startup.  This is useful mainly when debugging

with

.BR -D .

.TP

.BI -a " authtype

Sets the authentication method to be used.

.I Authtype

should be

.BR rhosts ,

.BR none ,

or

.BR p9any .

The default is

.BR rhosts ,

which uses the

.I ruserok

library call to authenticate users by entries in

.B /etc/hosts.equiv

or

.BR $HOME/.rhosts .

This default is discouraged for all but the most controlled networks.

Specifying

.B none

turns off authentication altogether.

This is useful when

.I u9fs

is not invoked from

.I inetd

(see examples below, or

.I srvssh

in

.IR srv (4)).

Specifying

.B p9any

uses the fourth edition Plan 9 authentication mechanisms.

The file

.BR /etc/u9fs.key ,

or

.I autharg

if specified

(see the

.B -A

option),

is consulted for the authentication data

and should be suitably protected.

This file must contain exactly three lines:

.I secret

(plaintext password),

.I u9fs-user

(user id),

and

.I plan9-auth.dom

(authentication domain).

.RS

.LP

Finally,

.I factotum

must be taught a key of the form:

.LP

.EX

.B

key proto=p9sk1 dom=\fIplan9-auth.dom\fP user=\fIu9fs-user\fP !password=\fIsecret\fP

.EE

.RE

.TP

.BI -A " autharg

Used to specify an argument to the authentication method.

See the authentication descriptions above.

.TP

.BI -l " logfile

Specifies the file which should contain debugging output

and other messages.

The out-of-the-box compile-time default is

.BR /tmp/u9fs.log .

.TP

.BI -m " msize

Set

.I msize

for 9P2000

(see

.IR open (5)).

.TP

.BI -u " user

Treat all attaches as coming from

.IR user .

This is useful in some cases when running without

.IR inetd ;

see the examples.

.PP

If

.I fsroot

is specified,

.I u9fs

will serve only that tree; othwise, it will serve the entire Unix

file system.

.SH EXAMPLES

.PP

Plan 9 calls 9P file service

.B 9fs

with TCP port number 564.

Set up this way on a machine called, say,

.BR kremvax ,

.I u9fs

may be connected to the name space of a Plan 9 process by

.IP

.EX

9fs kremvax

.EE

.PP

For more information on this procedure, see

.IR srv (4)

and

.IR bind (1).

.PP

By default,

.I u9fs

serves the entire file system of the Unix machine.

It forbids access to devices

because the program is single-threaded and may block unpredictably.

Using the

.B attach

specifier

.B device

connects to a file system identical to the usual system except

it only permits device access (and may block unpredictably):

.IP

.EX

srv tcp!kremvax!9fs

mount -c /srv/tcp!kremvax!9fs /n/kremvax device

.EE

.PP

(The

.B 9fs

command

does not accept an attach specifier.)

Even so,

device access may produce unpredictable

results if the block size of the device is greater than 8192,

the maximum data size of a 9P message.

.PP

The source to

.I u9fs

is in the Plan 9 directory

.BR /sys/src/cmd/unix/u9fs .

To install

.I u9fs

on a Unix system with an ANSI C compiler, copy the source to a directory on that system

and run

.BR make .

Then install the binary in

.BR /usr/etc/u9fs .

Add this line to

.BR inetd.conf :

.IP

.EX

9fs     stream  tcp     nowait  root   /usr/etc/u9fs   u9fs

.EE

.PP

and this to

.BR services :

.IP

.EX

9fs     564/tcp       9fs  # Plan 9 fs

.EE

.LP

Due to a bug in their

IP software, some systems will not accept the service name

.BR 9fs ,

thinking it

a service number because of the initial digit.

If so, run the service as

.B u9fs

or

.BR 564 .

.PP

On systems where listeners cannot be started,

.IR execnet (4)

is useful for running

.I u9fs

via other network mechanisms; the script

.I srvssh

in

.IR srv (4)

provides this for the

.I ssh

protocol.

.SH SOURCE

.B /sys/src/cmd/unix/u9fs

.SH DIAGNOSTICS

Problems are reported to the

log file specified with the

.B -l

option (default

.BR /tmp/u9fs.log ).

The

.B -D

flag enables chatty debugging.

.SH SEE ALSO

.IR bind (1),

.IR execnet (4),

.IR srv (4),

.IR ip (3),

.IR nfsserver (8)

.SH BUGS

The implementation of devices is unsatisfactory.

.LP

Semantics like remove-on-close or the

atomicity of

.B wstat

are hard to provide exactly.