Synchrony Frequently Asked Questions

Questions

  1. Can the server and client be using different operating systems?
  2. What does "Cannot initialize hook library" mean?
  3. What security/encryption does synchrony provide?
  4. What should I call my screens in the configuration?
  5. Can synchrony share the display in addition to the mouse and keyboard?
  6. My client can't connect. What's wrong?
  7. Linking fails on Solaris. What's wrong?
  8. I get the error 'Xlib: No protocol specified'. Why?
  9. The cursor goes to secondary screen but won't come back. Why?
  10. The cursor wraps from one edge of the screen to the opposite. Why?

Answers

  1. Can the server and client be using different operating systems?

    Yes. The synchrony network protocol is platform neutral so synchrony doesn't care what operating systems are running on the server and clients.

  2. What does "Cannot initialize hook library" mean?

    This error can occur on a synchrony server running on a Microsoft Windows operating system. It means that synchrony is already running or possibly was not shut down properly. If it's running then first end the synchrony task. If it's not then try logging off and back on or rebooting then starting synchrony again.

  3. What security/encryption does synchrony provide?

    Synchrony provides no built-in encryption or authentication. Given that, synchrony should not be used on or over any untrusted network, especially the Internet. It's generally fine for home networks. Future versions may provide built-in encryption and authentication.

    Strong encryption and authentication is available through SSH (secure shell). Run the SSH daemon (i.e. server) on the same computer that you run the synchrony server. It requires no special configuration to support synchrony. On each synchrony client system, run SSH with port forwarding:

            ssh -f -N -L 24800:server-hostname:24800 server-hostname
    

    where server-hostname is the name of the SSH/synchrony server. Once ssh authenticates itself, start the synchrony client normally except use localhost or 127.0.0.1 as the server's address. SSH will then encrypt all communication on behalf of synchrony. Authentication is handled by the SSH authentication.

    A free implementation of SSH for Linux and many Unix systems is OpenSSH. For Windows there's a port of OpenSSH using Cygwin.

  4. What should I call my screens in the configuration?

    You can use any unique name in the configuration file for each screen but it's easiest to use the hostname of the computer. That's the computer name not including the domain. For example, a computer with the fully qualified domain name xyz.foo.com has the hostname xyz. There should also be an alias for xyz to xyz.foo.com. If you don't use the computer's hostname, you have to tell synchrony the name of the screen using a command line option, or the startup dialog on Windows.

    Some systems are configured to report the fully qualified domain name as the hostname. For those systems it will be easier to use the FQDN as the screen name. Also note that a Mac OS X system named xyz may report its hostname as xyz.local. If that's the case for you then use xyz.local as the screen name.

  5. Can synchrony share the display in addition to the mouse and keyboard?

    No. Synchrony is a KM solution not a KVM (keyboard, video, mouse) solution. However, future versions will probably support KVM. Hopefully, this will make synchrony suitable for managing large numbers of headless servers.

  6. My client can't connect. What's wrong?

    A common mistake when starting the client is to give the wrong server host name. The last synchronyc command line option (Unix) or the "Server Host Name" edit field (Windows) should be the host name (or IP address) of the server not the client's host name. If you get the error connection failed: cannot connect socket followed by the attempt to connect was forcefully rejected or connection refused then the server isn't started, can't bind the address, or the client is connecting to the wrong host name/address or port. See the troublshooting page for more help.

  7. Linking fails on Solaris. What's wrong?

    Did you add

            --x-includes=/usr/openwin/include --x-libraries=/usr/openwin/lib
    

    to the configure command line? Solaris puts the X11 includes and libraries in an unusual place and the above lets synchrony find them.

  8. I get the error 'Xlib: No protocol specified'. Why?

    You're running synchrony without authorization to connect to the X display. Typically the reason is running synchrony as root when logged in as non-root. Just run synchrony as the same user that's logged in.

  9. The cursor goes to secondary screen but won't come back. Why?

    Your configuration is incorrect. You must indicate the neighbors of every screen. Just because you've configured 'Apple' to be to the left of 'Orange' does not mean that 'Orange' is to the right of 'Apple'. You must provide both in the configuration.

  10. The cursor wraps from one edge of the screen to the opposite. Why?

    Because you told it to. If you list 'Orange' to be to the left of 'Orange' then moving the mouse off the left edge of 'Orange' will make it jump to the right edge. Remove the offending line from the configuration if you don't want that behavior.