On 1/9/2012 5:20 AM, Mark Wendt wrote: > On 01/08/2012 06:27 PM, Kent A. Reed wrote: >> I had a few minutes this afternoon and decided to try another experiment >> with this board---still running Ubuntu 10.04LTS with the 2.6.32-122-rtai >> kernel. >> >> I disabled Gnome (which shut down X) on the board by running the following >> from the command line: >> >> sudo service gdm stop >> >> (I disabled a few other services too, like Apache, but I don't think this is >> relevant. The stock Ubuntu/EMC2 install starts up far too many services for >> my taste. When I want a controller, that's all I want, not a desktop >> computer.) >> >> Then I logged out and disconnected keyboard/mouse/monitor (well, actually I >> just set my KVM switch to another computer; possibly it still imposes some >> electrical levels at the motherboard connectors.) >> >> Finally, I logged into the board via Ethernet from another computer using >> ssh -Y and again ran the latency-test for 15 minutes with approximately the >> same level of stress as before (2 copies of glxgear, web browsing, listing >> the directories of an external USB drive, etc.). >> >> Bottom line: the latency numbers got even better. Max jitter fell to >> 3211ns/3222ns. >> >> For some time I have envisioned running my tabletop mill with a headless >> controller and a networked operator console. If anything, the present result >> says this would be the preferred mode. Of course, I could make it cleaner by >> stripping down the distribution some more, possible even install RTAI and >> EMC2 over a Ubuntu server distribution to avoid the Gnome/X-server stuff >> altogether, since there's the usual niff-naff about booting Ubuntu desktop >> edition without a monitor attached, etc. >> >> I'm curious if anyone has tried this experiment with other boards and, if >> so, what results were obtained. >> >> And, yes, I realize I am chasing after diminishing returns. The latency on a >> stock board is already good enough for practical purposes. Let's just say my >> home situation causes a form of ADHD were I work furiously on very >> short-term projects. >> >> Regards, >> Kent >> > Kent, > > Just curious, while headless, which runlevel were you at? You're still > going to have to run some form of X to get a remote display, and to do > that you need to be at either runlevel 5 or kick off startx. You can > run "init 3" to bring it down to a non-X runlevel, but you won't be able > to run Axis remotely without X running on the headless system. > > Mark > Mark:
For me, runlevels are tricky---every Unix variant seems to come with its own idea of what's what, and recent Ubuntu distributions replace the traditional init approach with the goings-on of a package called Upstart. Unmodified, my system reports the current runlevel is "2" and the previous runlevel is "N" (meaning, there was no previous runlevel recorded in the utmp record). In the end, runlevels are just a convenient way to manage the starting and stopping of services. For my test I decided to kill the service(s) I didn't want running using the "service" command (alternatively, I could have downloaded and used the rcconf tool). The runlevel remained "2". Remember, X11 apps are perfectly happy to run on a headless machine if they are talking to a remote X11-server. Their only requirement is the local presence of appropriate libraries (assuming the apps are dynamically linked, that is). X11's intrinsic network-communication model is massive overkill for single-machine applications but it's there precisely to support multi-machine environments. Regards, Kent ------------------------------------------------------------------------------ Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
