Notes:

  • The following configuration was employed on XenServer 6.0.2, but should work on XenServer 5.x as well (really based on guest OS, not hypervisor version)
  • The following was employed in a CentOS 5.8 VM. Due to version differences, implementing this on other versions of CentOS/RHEL may require modifications.
  • The solution has not been rigorously tested and is not supported by Citrix.
  • This article does not go into detail on how to use the Linux command line. Please refer to Linux documentation for further information if necessary.
  • This article does not go into detail on the installation of the RGS Receiver. Refer to HP’s documentation to accomplish this task.

Background:

Citrix has a fantastic presence in the desktop virtualization market with XenDesktop, but that only applies to Windows desktops. What if you wanted to deploy Linux desktops and use a remote display protocol to have your users reach them? Well, from a XenDesktop perspective, you can’t! ATM, ICA hasn’t been implemented on Linux, but there are a couple alternative options available, and the one I’ll be covering in this post is HP’s RGS protocol.

To be clear, I’ll explain how to install RGS into a paravirtual (PV) Linux VM running on XenServer. Not being an RGS expert, I believe there to be a couple of nuances with this approach (if you know otherwise, please correct me :-)):

  • RGS likes to use hardware acceleration. ATM, XenServer supports GPU passthrough to Windows VMs, but not Linux VMs. Therefore, we’re going to fake Linux out.
  • Due to the lack of GPU hardware in the VM, I would expect an increased load on the CPU, and therefore a decreased scalability. I have not gathered nor analyzed the statistics, so this is just my expectation.
  • This solution is just remote presentation of a Linux VM. It does not include any kind of desktop broker or management framework — the elements you really need in a true desktop virtualization solution.

Now, let’s get started!

Procedure:

Create a CentOS VM and install CentOS in the normal XenServer fashion. When I create VMs I typically create bare bones VMs that I convert to template, thereby allowing me to reuse the base install for any purpose. Making the assumption that you’ve created a generic CentOS VM with no package groups installed, you’ll first need to install the X Window System and the desktop of your choice (I chose Gnome):

yum groupinstall "GNOME Desktop Environment" "X Window System"

X Windows typically expects there to be a graphics card installed, but in a PV VM there isn’t a graphics card for X to use. Therefore, we need to trick it out by using a special “dummy” driver. This driver is typically used for development testing, but will allow us to configure X in our VM without having a real graphics card. Copy the following information into /etc/X11/xorg.conf:

xorg.conf
Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
    FontPath        "unix/:7100"
EndSection

Section "Module"
    Load           "dbe"
    Load           "extmod"
    Load           "type1"
    Load           "freetype"
    Load           "dri"
    Load           "glx"
#    Load           "vnc"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/input/mice"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from data in "/etc/sysconfig/keyboard"
    Identifier     "Keyboard0"
    Driver         "kbd"
    Option         "XkbLayout" "us"
    Option         "XkbModel" "pc105"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync   10.0 - 300.0
    VertRefresh 10.0 - 200.0
    #The following modeline is invalid (calculator overflowed):
    #Modeline "32000x32000@0" -38917.43 32000 32032 -115848 -115816 32000 32775 32826 33601
    Modeline "16384x8192@10" 2101.93 16384 16416 24400 24432 8192 8390 8403 8602
    Modeline "8192x4096@10" 424.46 8192 8224 9832 9864 4096 4195 4202 4301
    Modeline "5120x3200@10" 199.75 5120 5152 5904 5936 3200 3277 3283 3361
    Modeline "3840x2880@10" 133.43 3840 3872 4376 4408 2880 2950 2955 3025
    Modeline "3840x2560@10" 116.93 3840 3872 4312 4344 2560 2622 2627 2689
    Modeline "3840x2048@10" 91.45 3840 3872 4216 4248 2048 2097 2101 2151
    Modeline "2048x2048@10" 49.47 2048 2080 2264 2296 2048 2097 2101 2151
    Modeline "2560x1600@10" 47.12 2560 2592 2768 2800 1600 1639 1642 1681
    Modeline "1920x1200@10" 26.28 1920 1952 2048 2080 1200 1229 1231 1261
    Modeline "1920x1080@10" 23.53 1920 1952 2040 2072 1080 1106 1108 1135
    Modeline "1680x1050@10" 20.08 1680 1712 1784 1816 1050 1075 1077 1103
    Modeline "1600x900@20" 33.92 1600 1632 1760 1792 900 921 924 946
    Modeline "1440x900@20" 30.66 1440 1472 1584 1616 900 921 924 946
    Modeline "1360x768@20" 24.49 1360 1392 1480 1512 768 786 789 807
    #common resolutions for android devices (both orientations):
    Modeline "800x1280@20" 25.89 800 832 928 960 1280 1310 1315 1345
    Modeline "1280x800@20" 24.15 1280 1312 1400 1432 800 819 822 841
    Modeline "720x1280@25" 30.22 720 752 864 896 1280 1309 1315 1345
    Modeline "1280x720@25" 27.41 1280 1312 1416 1448 720 737 740 757
    Modeline "768x1024@25" 24.93 768 800 888 920 1024 1047 1052 1076
    Modeline "1024x768@25" 23.77 1024 1056 1144 1176 768 785 789 807
    Modeline "600x1024@25" 19.90 600 632 704 736 1024 1047 1052 1076
    Modeline "1024x600@25" 18.26 1024 1056 1120 1152 600 614 617 631
    Modeline "536x960@25" 16.74 536 568 624 656 960 982 986 1009
    Modeline "960x536@25" 15.23 960 992 1048 1080 536 548 551 563
    Modeline "600x800@25" 15.17 600 632 688 720 800 818 822 841
    Modeline "800x600@25" 14.50 800 832 880 912 600 614 617 631
    Modeline "480x854@25" 13.34 480 512 560 592 854 873 877 897
    Modeline "848x480@25" 12.09 848 880 920 952 480 491 493 505
    Modeline "480x800@25" 12.43 480 512 552 584 800 818 822 841
    Modeline "800x480@25" 11.46 800 832 872 904 480 491 493 505
    Modeline "320x480@50" 10.73 320 352 392 424 480 490 494 505
    Modeline "480x320@50" 9.79 480 512 544 576 320 327 330 337
    Modeline "240x400@50" 6.96 240 272 296 328 400 408 412 421
    Modeline "400x240@50" 6.17 400 432 448 480 240 245 247 253
    Modeline "240x320@50" 5.47 240 272 288 320 320 327 330 337
    Modeline "320x240@50" 5.10 320 352 368 400 240 245 247 253
    #resolutions for android devices (both orientations)
    #minus the status bar
    #38px status bar (and width rounded up)
    Modeline "800x1242@20" 25.03 800 832 920 952 1242 1271 1275 1305
    Modeline "1280x762@20" 22.93 1280 1312 1392 1424 762 780 783 801  
    Modeline "720x1242@25" 29.20 720 752 856 888 1242 1271 1276 1305
    Modeline "1280x682@25" 25.85 1280 1312 1408 1440 682 698 701 717
    Modeline "768x986@25" 23.90 768 800 888 920 986 1009 1013 1036
    Modeline "1024x730@25" 22.50 1024 1056 1136 1168 730 747 750 767  
    Modeline "600x986@25" 19.07 600 632 704 736 986 1009 1013 1036
    Modeline "1024x562@25" 17.03 1024 1056 1120 1152 562 575 578 591
    Modeline "536x922@25" 16.01 536 568 624 656 922 943 947 969
    Modeline "960x498@25" 14.09 960 992 1040 1072 498 509 511 523
    Modeline "600x762@25" 14.39 600 632 680 712 762 779 783 801
    Modeline "800x562@25" 13.52 800 832 880 912 562 575 578 591
    Modeline "480x810@25" 12.59 480 512 552 584 810 828 832 851
    Modeline "848x442@25" 11.09 848 880 920 952 442 452 454 465
    Modeline "480x762@25" 11.79 480 512 552 584 762 779 783 801
    Modeline "800x442@25" 10.51 800 832 864 896 442 452 454 465
    #32px status bar (no need for rounding):
    Modeline "320x448@50" 9.93 320 352 384 416 448 457 461 471
    Modeline "480x288@50" 8.75 480 512 544 576 288 294 297 303
    #24px status bar:
    Modeline "240x376@50" 6.49 240 272 296 328 376 384 387 395
    Modeline "400x216@50" 5.50 400 432 448 480 216 220 222 227
    Modeline "240x296@50" 5.02 240 272 288 320 296 302 305 311
    Modeline "320x216@50" 4.55 320 352 368 400 216 220 222 227
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "dummy"
    VendorName     "Dummy Device"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Viewport 0 0
#        Modes "32000x32000" "16384x8192" "8192x4096" "5120x3200" "3840x2880" "3840x2560" "3840x2048" "2048x2048" "2560x1600" "1920x1440" "1920x1200" "1920x1080" "1600x1200" "1680x1050" "1600x900" "1400x1050" "1440x900" "1280x1024" "1366x768" "1280x800" "1024x768" "1024x600" "800x600" "320x200"
        Modes "1280x1024" "1024x768"
        Depth       24
    EndSubSection
#    Option "SecurityTypes" "None"
EndSection

You can now test to make sure X doesn’t error out when started:

startx

Assuming everything is good, type ctrl-C to kill X.

Next you need to download the RGS software and your license and get them into the VM (I use scp), then navigate to the directory where you dropped it to install the RGS Sender:

mkdir RGS
cd RGS
tar xzvf ../RGS-Linux_5.4.8_tar.gz_Z7550-00538.tar.gz
cd lin64/sender/
./install.sh

Note: During install you will be asked if you want to configure the connection to a FlexLM server. If you haven’t set up a FlexLM server (the Citrix one doesn’t work properly — at least at first touch) you can install the license file on the server post-install using the following command:

cp ~/.lic /etc/opt/hpremote/rgsender/

Now you’re ready to test. Start GDM and then connect from an RGS Receiver on another machine:

gdm

Assuming everything works, you can stop GDM and modify the system to start at runlevel 5 (graphical mode):

gdm-stop
vi /etc/inittab

Change this:

id:3:initdefault:

To this:

id:5:initdefault:

Then reboot:

reboot

XenCenter Graphical Display:

If you also want the Graphical Display button to work in XenCenter (probably not, since any admin could see the user’s screen) you can uncomment the following two lines in /etc/X11/xorg.conf and either reboot or restart GDM:

Section "Module"
...
#    Load           "vnc"
EndSection

Section "Screen"
...
#    Option "SecurityTypes" "None"
EndSection

Note that this is NOT the preferred way of implementing VNC for use with XenCenter, and therefore there are a couple of annoyances when using the XenCenter-integrated graphical console (i.e. – VNC password prompts — just cancel them).