.TH IMPORT 4
.SH NAME
import \- import a name space from a remote system
.SH SYNOPSIS
.B import
[
.I options
]
.I system
.I file
[
.I mountpoint
]
.PP
.B import
.B -m
[
.I options
]
.I system
.I mountpoint
.PP
.B import
.B -B
[
.I options
]
.I mountpoint
[
.I cmd
[
.I args ...
]
]
.SH DESCRIPTION
.I Import
allows an arbitrary
.I file
on a remote
.I system
to be imported into the local name space.
Usually
.I file
is a directory, so the complete
file tree under the directory is made available.
.PP
A process is started on the
remote machine, with authority of the user of
.IR import ,
to perform work for the local machine using the
.IR exportfs (4)
service.
The default port used is TCP 17007.
If
.I mountpoint
is omitted
.I import
uses the name of the remote
.I file
as the local mount point.
.PP
The options are:
.TF "-s namexxx"
.PD
.TP
.B -a -b -c -C
Control the construction of union directories, as in
.I mount
and
.IR bind (1).
Only valid when 
.I file
is a directory.
.TP
.B -A
Skip the authentication protocol.
This is useful for connecting to foreign systems like Inferno.
.TP
.B -B
Run in ``backwards'' mode, described below.
.TP
.B -E \fIenc
Push an authentication protocol on its network connection.
The supported protocols are
.B clear
(the default, no protocol)
and
.BR ssl .
There are plans to make
.B tls
available.
.TP
.B -e '\fIenc auth\fR'
Specify the encryption and authentication algorithms to use for
encrypting the wire traffic
(see
.IR ssl (3)).
The defaults are
.B rc4_256
and
.BR sha1 .
.TP
.B -k \fIkeypattern
Use
.I keypattern
to select a key to authenticate to the remote side
(see
.IR auth (2)).
.TP
.B -o -O
These equivalent flags run
.I import
in a pre-9P2000 compatibility mode to import from ancient servers.
.TP
.B -p
Push the
.IR aan (8)
filter onto the connection to protect against
temporary network outages.
.TP
.B -s \fIname
Post the connection's mountable file descriptor as
.BI /srv/ name\fR.
.PD
.PP
The
.B -m
option mounts a file exported by
.IR exportfs (4)
with its
.B -r
or
.B -S
options, which skip the part of its protocol that allows the importer to specify
the
.I file
to export.
Instead, the file or name space is selected by
.IR exportfs ,
and
.I import
mounts it on
.I mountpoint
as guided by the other
.IR options .
.PP
The 
.B -B
option runs
.I import
in ``backwards'' mode.
In this mode,
.I import
runs a
.I p9any
authentication (as server) over its file descriptor 0
(expected to be an incoming network connection from
.B exportfs
.BR -B ),
mounts the connection onto
.IR mntpt ,
and optionally runs
.I cmd
.IR args .
.SH EXAMPLES
Assume a machine
.B kremvax
that has IP interfaces for the company intranet and the global
internet mounted on
.I /net
and
.I /net.alt
respectively.
Any machine inside the company can get telnet out to the global
internet using:
.IP
.EX
import -a kremvax /net.alt
telnet /net.alt/tcp!ucbvax
.EE
.PP
Suppose that the machine
.B moscvax
has access to a private file server containing public web pages
that need to be served by the less-trusted server
.BR webvax .
.B Webvax
runs the following listener 
(see
.IR listen (8))
on TCP port 999:
.IP
.EX
#!/bin/rc
import -B -s rowebfs /usr/web /bin/restarthttpd
.EE
.PP
When
.B moscvax
boots, it runs
.IP
.EX
exportfs -R -r /usr/web -B tcp!webvax!999
.EE
.PP
to serve a read-only copy of
.B /usr/web
to
.BR webvax .
When
.B webvax
gets the call, 
.B import
mounts the served tree onto its own
.B /usr/web
and then runs
.B /bin/restarthttpd
to restart
.IR httpd (8).
.SH SOURCE
.B /sys/src/cmd/import.c
.SH SEE ALSO
.IR bind (1),
.IR ssl (3),
.IR exportfs (4),
.IR srv (4),
.IR aan (8),
.IR listen (8),
.B cs
in
.IR ndb (8)