Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm able to connect using Rexec with X11 forwarding from a Windows PC using Mocha, however I need to find a method of achieving the same from a Mac.

I doubt it makes any difference, but the remote host runs VMS.

Can anyone offer any pointers to get me up and running?

share|improve this question
up vote 3 down vote accepted

Well I'm not familiar with Rexec, but if it's a standard x11 program then this should hopefully work.

First you'll need to install X11 on your Mac. I don't think there's a stand alone installer available for download, but you should be able to install it from your Mac OS X Installation disk. Should say something like Optional Extras.

I personally just install the full Xcode developer tools package which installs a bunch of required software for installing software from source code.

Next you'll need to to ssh to the box that will be running the X11 app. Open Terminal (in Application > Utilities) and run the ssh command with the -Y flag (I used -Y instead of -X for security reasons. If this doesn't seem to work you can use ssh -X instead, but it's not recommended. See the man page on ssh.):

ssh -Y username@hostname

Once logged in you can run the app from the command line (if it's in your $PATH):


Hopefully that's all you need to do. You might have better luck doing those two commands from xterm (instead of Terminal). For more information on X11 forwarding from/to a Mac check out Configuring and Running X11 Applications on Mac OS X from Apple's website.

share|improve this answer
Thanks. I've added X11 from my install disk, unfortunately SSH isn't an option on the remote host. I can telnet into the host, but that won't give me X forwarding. I'm told the way to connect to get X forwarding to work is via rexec (512/TCP). Much like yourself, I'm not familiar with rexec at all. – Bryan Feb 27 '10 at 16:12
Why is SSH not an option? – grawity Feb 27 '10 at 17:47
@Grawity: The host is a part of a industrial control system. We can't simply make changes without going through lengthy approval processes and testing. If there was a requirement for a change, it isn't a problem, but asking to add SSH just so I can connect from my mac isn't going to be approved. I can connect via a windows PC, so it isn't a problem, it would just be nice not to have to use a Virtual Machine or to have to dig my laptop out. – Bryan Feb 28 '10 at 11:53
Bryan: You could try pushing SSH as a "security improvement" (which it is; rexec and the like are quite insecure)... Anyway. In Unix-like server systems, you could set the remote $DISPLAY variable to, say,, where was your own external IP -- then X11 connections would be made directly over TCP. On VMS, seems to have the answer. Don't forget to configure your X server (Mocha) and your router to accept X11 connections. – grawity Feb 28 '10 at 14:11

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.