20110512-2213
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charles forsyth
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864baf1d4f
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.TH U9FS 4
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.SH NAME
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u9fs \- serve 9P from Unix
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.SH SYNOPSIS
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.B u9fs
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[
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.B -Dnz
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]
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[
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.B -a
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.I authtype
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]
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[
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.B -A
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.I autharg
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]
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[
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.B -l
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.I logfile
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]
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[
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.B -m
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.I msize
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]
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[
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.B -u
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.I onlyuser
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]
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.I fsroot
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.SH DESCRIPTION
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.I U9fs
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is
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.I not
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a Plan 9 program. Instead it is a program that
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serves Unix files to Plan 9 machines using the 9P protocol
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(see
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.IR intro (5)).
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It is typically invoked on a
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Unix machine by
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.B inetd
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with its standard input and output connected to a
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network connection, typically TCP on an Ethernet.
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It typically runs as user
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.B root
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and multiplexes access to multiple Plan 9 clients over the single wire.
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It assumes Plan 9 uids match Unix login names,
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and changes to the corresponding Unix effective uid when processing requests.
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Characters in file and directory names unacceptable to Plan 9 are translated
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into a three-character sequence:
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.L \e
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followed by two hexadecimal digits.
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.I U9fs
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serves both 9P1 (the 9P protocol as used by
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the second and third editions of Plan 9) and 9P2000.
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.PP
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The options are:
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.TF "\fL-A \fIautharg"
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.PD
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.TP
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.B -D
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Write very chatty debugging output to the log file (see
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.B -l
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option below).
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.TP
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.B -n
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Signals that
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.I u9fs
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is
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.I not
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being invoked with a network connection
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on standard input and output, and thus should
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not try to determine the remote address of the connection.
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This is useful when
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.I u9fs
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is not invoked from
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.I inetd
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(see examples below).
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.TP
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.B -z
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Truncate the log file on startup. This is useful mainly when debugging
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with
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.BR -D .
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.TP
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.BI -a " authtype
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Sets the authentication method to be used.
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.I Authtype
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should be
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.BR rhosts ,
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.BR none ,
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or
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.BR p9any .
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The default is
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.BR rhosts ,
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which uses the
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.I ruserok
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library call to authenticate users by entries in
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.B /etc/hosts.equiv
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or
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.BR $HOME/.rhosts .
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This default is discouraged for all but the most controlled networks.
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Specifying
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.B none
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turns off authentication altogether.
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This is useful when
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.I u9fs
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is not invoked from
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.I inetd
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(see examples below, or
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.I srvssh
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in
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.IR srv (4)).
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Specifying
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.B p9any
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uses the fourth edition Plan 9 authentication mechanisms.
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The file
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.BR /etc/u9fs.key ,
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or
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.I autharg
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if specified
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(see the
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.B -A
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option),
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is consulted for the authentication data
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and should be suitably protected.
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This file must contain exactly three lines:
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.I secret
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(plaintext password),
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.I u9fs-user
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(user id),
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and
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.I plan9-auth.dom
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(authentication domain).
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.RS
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.LP
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Finally,
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.I factotum
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must be taught a key of the form:
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.LP
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.EX
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.B
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key proto=p9sk1 dom=\fIplan9-auth.dom\fP user=\fIu9fs-user\fP !password=\fIsecret\fP
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.EE
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.RE
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.TP
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.BI -A " autharg
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Used to specify an argument to the authentication method.
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See the authentication descriptions above.
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.TP
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.BI -l " logfile
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Specifies the file which should contain debugging output
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and other messages.
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The out-of-the-box compile-time default is
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.BR /tmp/u9fs.log .
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.TP
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.BI -m " msize
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Set
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.I msize
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for 9P2000
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(see
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.IR open (5)).
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.TP
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.BI -u " user
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Treat all attaches as coming from
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.IR user .
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This is useful in some cases when running without
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.IR inetd ;
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see the examples.
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.PP
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If
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.I fsroot
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is specified,
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.I u9fs
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will serve only that tree; othwise, it will serve the entire Unix
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file system.
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.SH EXAMPLES
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.PP
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Plan 9 calls 9P file service
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.B 9fs
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with TCP port number 564.
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Set up this way on a machine called, say,
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.BR kremvax ,
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.I u9fs
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may be connected to the name space of a Plan 9 process by
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.IP
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.EX
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9fs kremvax
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.EE
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.PP
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For more information on this procedure, see
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.IR srv (4)
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and
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.IR bind (1).
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.PP
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By default,
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.I u9fs
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serves the entire file system of the Unix machine.
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It forbids access to devices
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because the program is single-threaded and may block unpredictably.
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Using the
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.B attach
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specifier
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.B device
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connects to a file system identical to the usual system except
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it only permits device access (and may block unpredictably):
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.IP
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.EX
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srv tcp!kremvax!9fs
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mount -c /srv/tcp!kremvax!9fs /n/kremvax device
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.EE
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.PP
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(The
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.B 9fs
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command
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does not accept an attach specifier.)
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Even so,
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device access may produce unpredictable
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results if the block size of the device is greater than 8192,
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the maximum data size of a 9P message.
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.PP
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The source to
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.I u9fs
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is in the Plan 9 directory
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.BR /sys/src/cmd/unix/u9fs .
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To install
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.I u9fs
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on a Unix system with an ANSI C compiler, copy the source to a directory on that system
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and run
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.BR make .
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Then install the binary in
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.BR /usr/etc/u9fs .
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Add this line to
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.BR inetd.conf :
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.IP
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.EX
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9fs stream tcp nowait root /usr/etc/u9fs u9fs
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.EE
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.PP
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and this to
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.BR services :
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.IP
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.EX
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9fs 564/tcp 9fs # Plan 9 fs
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.EE
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.LP
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Due to a bug in their
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IP software, some systems will not accept the service name
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.BR 9fs ,
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thinking it
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a service number because of the initial digit.
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If so, run the service as
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.B u9fs
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or
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.BR 564 .
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.PP
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On systems where listeners cannot be started,
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.IR execnet (4)
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is useful for running
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.I u9fs
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via other network mechanisms; the script
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.I srvssh
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in
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.IR srv (4)
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provides this for the
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.I ssh
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protocol.
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.SH SOURCE
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.B /sys/src/cmd/unix/u9fs
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.SH DIAGNOSTICS
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Problems are reported to the
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log file specified with the
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.B -l
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option (default
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.BR /tmp/u9fs.log ).
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The
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.B -D
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flag enables chatty debugging.
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.SH SEE ALSO
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.IR bind (1),
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.IR execnet (4),
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.IR srv (4),
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.IR ip (3),
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.IR nfsserver (8)
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.SH BUGS
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The implementation of devices is unsatisfactory.
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.LP
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Semantics like remove-on-close or the
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atomicity of
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.B wstat
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are hard to provide exactly.
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