Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.astro.louisville.edu/software/xmtel/archive/xmtel-5.1/REMOTE Дата изменения: Thu Oct 29 22:03:13 2009 Дата индексирования: Mon Oct 1 20:55:16 2012 Кодировка: Поисковые слова: arp 220

Using X11 remotely
==================

SecureShell (SSH) will securely transport an X-windows graphical user interface
across the network. The command to use this feature is

ssh -Y user@remoteserver

if SSH is configured to support it (see below). The "-Y" flag is used for
trusted host connections. A similar "-X" flag is available. Use "man ssh" for
more information.

This technique works well only on a gigabit network with low latency. Over long
distances, regardless of the network capacity, the lag between command and
response (latency) due to transit time becomes unacceptable. Therefore unless
this software is being used on a high speed local area network, we recommend
running indiserver on a computer at the telescope, and clients on the
observer's computer. The server and the clients communicate with XML, are
tolerant of latency, and do not require a high speed connection.

If you are controlling the server from a remote location for this purpose it is
recommended that you do NOT transport X over the connection used to run the
server. You will connect to the server (telescope) computer with a command such
as the one described below:

ssh -L 7624:localhost:7624 user@remoteserver

On a high speed local area network if you also want to transport X you may
connect with

ssh -Y -L 7624:localhost:7624 user@remoteserver


Configure SSH without passwords
===============================

On the computer you are connecting from

ssh-keygen -t dsa

generated two files in $HOME/.ssh

-rw------- id_dsa
-rw-r--r-- id_dsa.pub

id_dsa is the private key and id_dsa.pub is the public key. Note the differences
in the default permissions.

Copy and append id_dsa.pub to

$HOME/.ssh/authorized_keys

on the system you are connecting to. This may be accomplished by the command
line

ssh-copy-id ./ssh/id_dsa.pub user@host

Note that id_dsa is the private key and id_dsa.pub is the public key. You
should copy only the public key to the remote system.


For reciprocal passwordless login, do this on both machines.


It may be necessary as root user or sudo to configure the file
/etc/ssh/ssh_config to have the entry

ForwardAgent yes

By default in Suse /etc/ssh/sshd_config will have

PubkeyAuthentication yes

so you won't have to change that, nor restart sshd.

If you are connecting from an observer's computer to a telescope computer that
is not on a local area network, you may also need to change the firewall
settings to enable SSH. For OpenSuse there is a YAST utility to manage the
firewall that will do this for you. Other distributions may use
/etc/hosts.allow and /etc/hosts.deny for access control.

Secure shell is very secure! However, once you open your computer to SSH
access, it is likely that someone will try to take advantage of the open
port and attempt to log in remotely. The simple technique of using a secure
password is usually all that is needed to protect your system. It is of course
much safer to include lines in the system /etc/hosts files to enable
access only from known IP addresses. Here's an example of how that would look.


hosts.deny hosts.allow
---------- -----------
ALL : ALL ssh: 192.168.1.1

The telescope computer's hosts.allow file would include the IP addresses for all
allowed remote users. Each remote user would include in their hosts.allow file
the IP address of the telescope computer. By using ALL in the hosts.deny file
you insure that only systems in hosts.allow are permitted to connect to this
computer.

These controls apply to incoming communications, not to outgoing communications.
The telescope and camera software require bidirectional transfer and therefore
systems at both ends of the connection must be properly configured.

Test the connection by "ssh user@remotehost" and it should not prompt for a
password when the contents of the user's .ssh and the system etc/ssh/ files
are correctly set. If a connection fails completely for ssh, it is likely the
problem is in the firewall or hosts files.


Server Port
===========

The XmCCD camera controller runs as an INDI device.
It will accept remote commands on port 7624.
To tunnel this port through SSH, initiate a passwordless session
from the client to the server with this command line:

ssh -L 7624:localhost:7624 user@remoteserver

Other ports may be opened at the same time, for example:

ssh -L 7624:localhost:7624 -L 6791:localhost:6791 user@remoteserver


Start the server
================

Apply power to the camera and telescope. For the SBIG camera when its fan has
started, the camera has loaded its firmware. You may check this with lsusb
from the command line to see the status of the usb interface. Once the camera
is powered on, start the indiserver with the camera driver using the
commandline:

indiserver ccd &

If you are using xmtel as well, start both camera and telescope drivers at
the same time:

indiserver tel ccd &

If you are running other indi devices, the command line would be, for example,

indiserver tel ccd dome guider &



Start the clients xmccd, xmtel, xmdome, xmguider and xephem
==========================================================

As a separate process on the local computer start xmccd with

xmccd &

The xmccd control panel will appear and the image display program ds9
will start automatically. Enable remote operation on the control panel.

For controlling your telescope xmtel and xephem are compatible with xmccd and
use the INDI protocol. The control panel available in xephem will also allow
you to control all aspects of the camera operation. Each may be started in a
separate request:

xmtel &
xephem &


Configure xephem
================

To use XEphem with INDI add the following to your configuration, either in
/etc/XEphem or in your home directory's .xephem/XEphem file:

XEphem*INDIConfig*GotoDecValue.value: tel.target_2000.dec
XEphem*INDIConfig*GotoRAValue.value: tel.target_2000.ra
XEphem*INDIConfig*SkyDecValue.value: tel.telescope_2000.dec
XEphem*INDIConfig*SkyRAValue.value: tel.telescope_2000.ra

These values may also be set in XEphem's telescope configuration menu in
under skyview. If you do it that when, when you close XEphem you will have
an option of saving the new configuration to your .xephem/XEphem file. If
you make the change by editing the /etc/XEphem file, it will be available to
all users by default.