While I haven’t tried pair programming I’m intrigued by the idea and would like to give it a shot some time. Rod Hilton recently blogged about his experiences with pair programming and despite vim (+command line) being my primary development environment I have to concede that it makes an interesting as well as entertaining read. As William Pietri noted in the comments the “insights on Programmer Man are both novel and keen” and well worth pondering even if you have no interest in pair programming per se.
I may not have said it outright, but I certainly implied that the primary form of orbital data available to operators for collision prediction purposes is Two-Line Elements (TLEs). Specifically the TLEs published by the US Air Force. There are of course other types of data, although they are either not publicly available or not comprehensive.
Here’s a rundown…
By “operator data” I mean whatever orbital data a satellite owner/operator uses for orbit control and/or prediction for its own spacecraft. This data is typically based on radiometric or GPS measurements and is much more accurate than TLE. The obvious shortcoming of operator data is that no such data exists for inactive spacecraft and debris orbiting Earth. Furthermore, satellite operators normally only have access to this information for their own spacecraft. Accurate knowledge of your own spacecraft’s orbit doesn’t really help much when you don’t have accurate information about all the other objects it might collide with.
In the geostationary realm, where the ratio of active spacecraft to debris is still relatively favorable, operators have recently started an effort to share data between themselves for purposes of collision avoidance. This is a unique cooperation among the otherwise very competitive telecommunication satellite owners (of which my employer, Intelsat, is one) and an important first step to safer satellite operations in the geostationary belt.
In lower orbits, such as those of Iridium 33 and Cosmos 2251, the ratio of operated spacecraft to debris is so small that sharing operator data would only marginally improve safety.
The US Air Force publishes a catalog of orbital data in the form of TLEs for the majority of Earth-orbiting objects through its space-track.org web site.
TLEs are based on measurements made by the US Space Surveillance Network (SSN). The measurements are fitted to a relatively simple analytical model (SGP4) by an undisclosed process. The accuracy of any given TLE is generally unknown, perhaps even to the Air Force. Factors affecting the orbit quality are:
- The amount and age of measurements used to generate the TLE,
- The applicability of the SGP4 model to the particular orbit and object properties,
- The presence of artificial disturbances (i.e. maneuvers) during or after the time when measurements were collected.
In general the accuracy of TLEs is thought to be on the order of kilometers. However, the TLE catalog also has other problems, notably that classified US spacecraft (and related debris) are purposefully omitted from the catalog and that certain classes of non-classified objects are omitted for technical reasons (e.g. inability to track them).
Special Perturbations (SP) data
SP data is the moniker for orbital data from a classified catalog maintained by the US Air Force. It is essentially equivalent to the TLE catalog but with higher accuracy data based on a more accurate orbital model. It also includes the classified US spacecraft. The accuracy of SP data isn’t publicly known but it is thought to be significantly better than that of the TLEs.
The SP data catalog is used routinely for collision prediction for the Air Force’s (and other DoD organizations’) satellites as well as NASA missions (notably human spaceflight). However, by virtue of being classified the SP data isn’t generally available to other satellite operators. There is a process through which satellite operators can request support from the Air Force to confirm isolated close approaches. This process currently requires the operator to first identify the risk of a close approach by another means (e.g. using TLEs) and then go through a few layers of bureaucracy before the Air Force will investigate the close approach. It works somewhat in the not-too-densely-populated geostationary realm but I cannot see that it would scale to the level of support e.g. Iridium would need.
One can only hope that the collision between Iridium 33 and Cosmos 2251 prompts the Air Force to increase the level of support it provides to satellite operators and streamline the processes involved.
The European Space Agency maintains the DISCOS database (Database and Information System Characterising Objects in Space) which is based primarily on data from the US Space Surveillance Network. I don’t know any details about that data, perhaps it is simply the TLEs that the US Air Force publishes?
Late last year ESA initiated a program to develop its own space tracking capabilities.
MIT Lincoln Laboratory
MIT’s Lincoln Laboratory offers a close approach prediction service to geostationary satellite operators. To my knowledge the data used in the predictions is collected by the laboratory’s own sensors and is comparable to SP data. It’s a good service but the cost for operators is pretty steep (though certainly nowhere near the cost of losing a satellite in a collision) which prevents its use from being ubiquitous.
International Scientific Optical Network
A relatively new player in this field is the International Scientific Optical Network (ISON) coordinated by the Keldysh Institute of Applied Mathematics in Moscow. ISON is a collaboration between 18 scientific institutions in 9 states with the objective of establishing and maintaining a comprehensive database of objects in high altitude orbits (including the geostationary belt). ISON has so far identified several hundred objects not included in the US Air Force’s TLE catalog (roughly half of which are classified US objects).
The quality of ISON’s orbital data seems to be significantly better than TLEs, but at present the networks focus is on tracking object not in the TLE catalog rather than providing comprehensive orbital data for collision prediction purposes. However, this is a player worth keeping an eye on if you are operating geostationary spacecraft.
There’s more to it…
As is obvious to anyone working with the problem of satellite close approach prediction and avoidance I done a lot of hand waving and sweeping generalizations in these posts. My intent was never to go into pain-staking detail or to expose every facet of the problems satellite operators face. I am certainly not aware of them all myself despite the problem being part of my everyday work (just today we decided to reschedule a maneuver on one of our satellites in order to maintain safe separation distance during an upcoming close approach with a spent rocket body).
In my previous post I discussed the difficulties satellite operators like Iridium face in attempting to predict collisions. I’ll talk more about orbital data in the future but in this post I want to revisit the question of whether it makes sense to point fingers at the Russians for having an “out of control” spacecraft (Cosmos 2251) on orbit? Well, one could turn the tables and argue that the finger should be pointed at Iridium, since their spacecraft (Iridium 33) had the capability to maneuver and also was an asset worth protecting. But, as I illustrated previously, it is extremely difficult for a satellite operator in this particular orbital regime (Low Earth Orbits) to predict collisions with high enough confidence to warrant action.
In fact, many satellites in Low Earth Orbits don’t even have a propulsion system, which means that even given perfect information regarding a future collision they would be unable to move out of the way. An example of such a satellite is the Swedish space observatory Odin which orbits Earth in a circular polar orbit roughly 600 km above sea level, or 180 km below the altitude at which Iridium 33 and Cosmos 2251 collided. Odin is built and operated by the Swedish Space Corporation, my former employer, and is particularly dear to me as I participated in its launch campaign at Svobodny Cosmodrome, Russia, in 2001.
About a year ago Dr T.S. Kelso told me that one day when he had been checking on the close approach predictions from his SOCRATES service he saw a miss distance significantly smaller than he had ever seen before. I don’t remember the exact number but I believe he said it was less than a meter, which is to say it is not a miss at all if the combined dimensions of the involved spacecraft are greater than a meter. One of the objects involved in the prediction was a piece of debris while the other was the still operational Odin. Even with the caveats regarding the inaccuracies of Two-Line Elements T.S. felt compelled to contact Odin’s, to him unknown, operator and warn them of the potential danger. After a fair bit of detective work he eventually got hold of a phone number to the Odin control center at Esrange in northern Sweden. He placed the call and explained the predicament only to find out that Odin did not have maneuvering capability and could do nothing to ameliorate the situation.
So how did it go? Well, since you haven’t heard of this before I don’t have to tell you there was no collision and Odin is still out there doing good science. But the example still serves to illustrate the inability to mitigate a predicted close approach, which would hold true even if the data behind the prediction was better. In light of the fact that many satellites don’t have a propulsion system by design (and consequently have no interest in, or can not benefit from, collision predictions) it appears unreasonable to place blame on Iridium for omission of action, or on the Russians for inability to act. These are just par for the course.
(Now, if there was such a thing as perfect information regarding collision prediction perhaps it would be worthwhile including a minimal propulsion system solely for the purpose of collision avoidance, even on spacecraft like Odin where a propulsion system is otherwise considered unnecessary. Alas, it is not so.)
The big news in my industry right now is the collision between the satellites Iridium 33 and Cosmos 2251. While the Cosmos spacecraft was reportedly non-operational since 1995 Iridium 33 was operational and in service.
In some of the press the choice of wording (e.g. “out of control” and “slammed into the Iridium craft”) has been such as to unfairly suggest that Cosmos 2251 was at fault. For example, from BBC News:
“A collision occurred between an Iridium 33 satellite and a Russian Cosmos 2251 military satellite,” Major General Alexander Yakushin said.
The satellite was launched in 1993 and ceased to function two years later, he said according to the AFP news agency.
Russia has not commented on claims the satellite was out of control.
The Russian Major General said that Cosmos 2251 ceased to function in (or around) 2005, so by definition it is “out of control,” which is to say it was orbiting the Earth as dictated by fairly well understood laws of physics. However, the term “out of control” is used by BBC (and others) in a way that implies that Cosmos 2251 is flying around all over the place in an unpredictable manner endangering other spacecraft left and right.
The truth is, it doesn’t really matter, this could just as well have happened between any two operational spacecraft. The key here is that in general, no one is looking. And even if you are looking, it is difficult to know what to do.
I first heard of the event about twelve hours after the fact from Dr T.S. Kelso at the Center for Space Standards & Innovation. Dr Kelso operates the venerable CelesTrak website and one of the services his site provides is SOCRATES (Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space). SOCRATES compares Two-Line Elements (parameters describing satellite orbits, hereafter referred to as TLEs) from the US Air Force in order to predict close approaches between objects in orbit around Earth. SOCRATES had predicted a close approach between Iridium 33 and Cosmos 2251 of 584 m at the time of collision. This highlights a significant problem: the data generally available to predict close approaches isn’t very accurate. The actual accuracies of any given TLEs are not well known, perhaps not even to the Air Force. In this case the data was obviously off by about 584 m (the satellites themselves may be up to tens of meters large).
So, should Iridium and other satellite operators look out for, and maneuver their satellites to avoid, anything that comes within a given distance of their own spacecraft? Apparently a 584 m predicted miss distance is not safe so for the sake of argument let’s assume that we use that as a safety threshold. Searching for “IRIDIUM” in SOCRATES right now returns 16 close approaches with distances less than 584 m over seven days:
|Time of Closest Approach (UTC)||Object 1||Object 2||Min Range (km)|
|2009 Feb 13 14:38:21||IRIDIUM 16||COSMOS 1275 DEB||0.137|
|2009 Feb 16 05:47:41||IRIDIUM 97||CBERS 1 (ZY 1A)||0.184|
|2009 Feb 13 03:22:09||IRIDIUM 16||FENGYUN 1C DEB||0.213|
|2009 Feb 15 23:59:47||IRIDIUM 45||SL–8 DEB||0.251|
|2009 Feb 12 19:38:39||IRIDIUM 24||COSMOS 1275 DEB||0.274|
|2009 Feb 12 07:19:35||IRIDIUM 26||NOAA 6||0.315|
|2009 Feb 12 14:18:32||IRIDIUM 36||CZ–4 DEB||0.348|
|2009 Feb 18 18:08:06||IRIDIUM 59||COSMOS 990||0.363|
|2009 Feb 16 00:12:50||IRIDIUM 54||THORAD AGENA D DEB||0.373|
|2009 Feb 17 07:48:07||IRIDIUM 38||DELTA 1 DEB||0.417|
|2009 Feb 17 06:36:02||IRIDIUM 50||ARIANE 40 R/B||0.483|
|2009 Feb 12 17:16:04||IRIDIUM 21||SL–8 DEB||0.490|
|2009 Feb 18 01:35:15||IRIDIUM 54||OPS 5058 (DMSP 5B F2)||0.491|
|2009 Feb 15 03:23:34||IRIDIUM 11||SL–18 DEB||0.495|
|2009 Feb 12 12:41:48||IRIDIUM 81||COSMOS 1190||0.555|
|2009 Feb 16 11:51:54||IRIDIUM 4||TITAN 3C TRANSTAGE DEB||0.578|
Note that none of the above include debris originating from the Iridium 33/Cosmos 2251 collision - most likely because the Air Force hasn’t begun to publish that data yet. And we’re only looking at close approaches involving the 92 Iridium spacecraft, while there are over 10000 known objects out there. Check out the SOCRATES Top 10 listings at any given time for even closer approaches. The point is that services like SOCRATES predict lots of close approaches where the miss distance is significantly below the known to be unsafe 584 m, but actual collisions are still extremely unlikely and (to date) extremely rare.
Now, from the point of the satellite operator it should be understood that maneuvering a satellite to avoid a conjunction generally carries a quantifiable monetary cost with it. If the available information is so inaccurate you don’t even know for sure if you’ll be improving the situation by maneuvering (which is often the case when the information is TLEs) chances are you’ll do nothing and hope for the best. Indeed, there is a good chance you won’t even bother looking.
What is needed to make it operationally feasible to react to predicted close approaches is better data. Operators like Iridium have to know that if the data says the miss distance is, say, 100 m they are safe, and that for the infrequent cases where the miss distance is less the risk is so high that it is worth doing the analysis and spending the fuel necessary for an avoidance maneuver.
I have more to say on this topic but it’s getting late. In the mean time, check out some visualizations courtesy of Analytical Graphics, Inc.
For background refer to my previous post.
Now I’m going to go into some detail of the Arch Linux (hereafter referred to as Arch) installation and configuration process, or at least how it played out for me. I won’t be addressing those parts where the Beginners Guide was crystal clear and everything went as expected. I will be addressing the parts where I got confused or alarmed or where things just weren’t working as I would have expected.
I should start off by mentioning the rather significant detail that I decided to install Arch as a guest OS running in VirtualBox under Windows XP. When I started out this seemed like a good idea; I wouldn’t have to worry about repartitioning the drive I currently had Windows XP on, I would be able to familiarize myself with Arch and how well it functions on the EEE PC before committing to it, it would be fun to try out VirtualBox, and if everything was hunky dory I hoped I could just take my VirtualBox disk image and clone it to a physical partition and be done. At that point I’d turn the tables and run Arch as my main OS while booting Windows XP as a VirtualBox guest OS on and as-needed basis.
Turns out I was naive. As I worked my way through the installation and configuration I realized that I’m failing to test how well Arch runs on the EEE PC. The stuff I would expect to be most problematic or difficult to configure doesn’t really come into play when running as guest OS. Video (including “compressed” 1024x768), sound, network cards, wifi, webcam, multi-touch trackpad, power management (including “Super Hybrid Engine”); all these are either not applicable or free-riding on the Windows drivers. I still have no idea how well all these things would work without Windows XP behind the scenes. In addition my Arch installation is configured for the mock hardware interfaces that VirtualBox exposes to it; for all I know it probably won’t run at all outside of VirtualBox!
Even had I realized the above I suspect I would still have chosen to install in VirtualBox first to try things out. Or perhaps I would have opted to try out another distro with a Live CD (or, more specifically, live thumb drive). Anyway, back to the Arch installation process…
It turned out the mistake that I was referring to in my previous post wasn’t as fatal as I feared. I was in the Configure the System section of the Beginners Guide and believe I had made my way through initramfs and was about to select /etc/rc.conf in the menu when I inadvertently hit the ESC key. This exited the menu and a bunch of processing commenced, entirely prematurely. I had just skipped the steps where the guide said (with emphasis as it appears in the guide):
Closely following and understanding these steps is of key importance to ensure a properly configured system.
and, a few paragraphs further down:
Note: It is very important at this point to edit, or at the very least, to verify by opening, every configuration file. The installer script relies on your input to create these files on your installation. A common error is to skip over these critical steps of configuration.
I was fully expecting to have to wipe everything out and restart the installation procedure from scratch. However, once the configuration was done I was returned to the main menu and, lo and behold, I could back up one step and chose to reconfigure. This I did, following the guide closely, and as far as I can tell all is well. Sometimes you get lucky.
General installation process
I decided to install off the most recent core ISO (archlinux–2008.06-core-i686.iso). The relative merits of core vs FTP were unclear at the time but I believe if you use the FTP ISO you’ll end up with an up to date system from the start, while I ended up with eight month old packages.
I’m not particularly fond of the fuzzy compressed mode or scrolling the screen so I chose
vga=771 to get 800x600 resolution instead of
vga=773 and 1024x768. I imagine that without VirtualBox the scrolling and compressed mode wouldn’t have been available at all in which case
vga=773 would be a very poor choice.
The first point of confusion arose when partitioning the hard drive. In the cfdisk interface a partition could be flagged as “bootable,” which sounds like it would be a desirable property for the partition with /boot filesystem. However, there is no mention of the flag in the Beginners Guide and in the example no flags are set on the partitions. I stayed true to the guide and didn’t set the flag and everything has worked fine. So while there isn’t an error per se in the guide it would be nice if it explicitly mentioned that the flag doesn’t need to be set. It certainly would have saved me some angst.
For the record I didn’t want to deal with deciding what is an appropriate size for all the file systems so I just went with one for / and a separate swap partition. It’s probably ridiculously easy to resize partitions after the fact but I wasn’t in a mood to investigate at the time.
At first I disabled crond in /etc/rc.conf but later realized I was missing out on good stuff like updatedb (necessary for locate to work) so I re-enabled it.
Setting up sound with alsa had me scratching my head for a while until I realized I had to enable sound for the guest in the VirtualBox settings.
I skipped part IV of the guide since I had already decided to use xmonad as my window manager. This was readily accomplished by
pacman -S xmonad and I continued with other packages: vim, texlive, firefox…
The first “discrepancy” I noticed occurred when pacman was “updating kernel-headers” after installing cairo. It reported the rather disconcerting message:
error: scriptlet failed to execute correctly
I don’t mean to imply that the message itself is terribly scary, scriptlet even has a cutesy ring to it, but I’d imagine its not good to have stuff going wrong when messing with your kernel. Anyway, I have no idea what that means or what the scriptlet that failed was supposed to do. The error didn’t show up in /var/log/pacman.log so I presumed it must have come from a build script external to pacman or something along those lines. The next time I saw a scriptlet fail was when updating shadow:
Fixing gshadow file... add group 'uucp' in /etc/gshadow ?grpck: the files have been updated error: scriptlet failed to execute correctly
Again not sure what that meant, nor what to do about it. Hoping it was nothing.
VirtualBox Guest Additions: Take One
At some point I realized that to get decent video drivers supporting the native 1024x600 resolution of the EEE PC I had to install the VirtualBox Guest Additions. I had the option of installing from the ISO that came with VirtualBox, but there were no instructions specifically for Arch. I saw mention in some forum of a virtualbox-ose-additions community package. Doing a
pacman -Si virtualbox-ose-additions revealed that it was version 2.0.4–1 while my installation of VirtualBox is 2.1.2. The build date was 2008–11–12 so I decided to try my luck hoping not much would have changed between the two versions, especially given that the ISO is an auxiliary part of VirtualBox. Well, I was stopped short by pacman:
error: failed to prepare transaction (could not satisfy dependencies) :: virtualbox-ose-additions-modules: requires kernel26<2.6.28>
I checked my kernel26 and it was version 184.108.40.206–1 which certainly seemed to comply with the stated requirement. However, a
pacman -Si virtualbox-ose-additions-modules revealed the following requirement:
Depends on : kernel26>=2.6.27 kernel26<2.6.28>
OK, my kernel26 didn’t fulfill the requirements, although the requirement reported wasn’t the one that was violated.
By now I was thinking maybe I should upgrade my kernel26. In fact, I was mildly surprised that pacman didn’t go ahead and do that for me. I checked with pacman and saw that the latest version of kernel26 is 220.127.116.11–1. It dawned upon me that the reason pacman reported the requirement
kernel26<2.6.28 was because that was the one that would have been violated had the kernel26 been upgraded to the latest version. Makes sense I guess but would have been nice if the error message was more explicit about it.
I decided to hit the AUR site to see if it could shed any additional light on these packages and indeed, there I saw that virtualbox-ose-additions had been flagged as out of date! I can’t help but wish that a pacman would reveal this rather important piece of information;
pacman -Si loses a lot of its appeal if I have to double-check each package on the web before installing. (One could argue that pacman implicitly “knows” this particular package is out of date by virtue of its dependencies being unsatisfiable, but I believe this is a special case; other packages may have been flagged e.g. for security reasons even though there dependencies are satisfiable.)
Recommendation: Always check package status in AUR before installing, especially before deciding to “try your luck.”
(I later realized that I was using the PUEL VirtualBox and not VirtualBox OSE so the packages in question may never have been applicable in the first place.)
Upgrading all packages
Given that the VirtualBox Guest Additions seem to be particular about the kernel version I decided that it would be a good idea to update the kernel and all my other packages before proceeding. A
pacman -Su identified 76 packages needing upgrades and started downloading (these are presumable the packages that were installed from the eight months old core ISO). Upon completion of the downloads pacman complained:
error: failed to commit transaction (conflicting files)
and listed a mass of files in /usr/lib/klibc/include/asm. A quick google revealed an announcement and fix for this:
rm /usr/lib/klibc/include/asm. Having removed the symlink all 76 packages upgraded just fine.
VirtualBox Guest Additions: Take Two
Back to the VirtualBox Guest Additions; it seemed my only option now was to install them from the ISO. I could either use the ISO provided with my Windows version of VirtualBox or I could install the virtualbox-additions package which to my understanding would just download the same ISO for me; I’d still have to mount it and install the actual software myself. I decided to go with the ISO that came with my VirtualBox.
I mounted the ISO in the VirtualBox Media Manager but when attempting to
mount /media/cdrom in Arch I was told that the cdrom was missing from /etc/fstab. This was perfectly true; the EEE PC has no optical drive so during Arch configuration I had left the cdrom commented out. At the time I hadn’t fully internalized the distinction between installing straight to the EEE PC vs installing on VirtualBox, and it hadn’t occurred to me that VirtualBox provided emulated optical drives. I uncommented the cdrom in /etc/fstab and it mounted without further drama.
The installation instructions for the VirtualBox Guest Additions were conflicting and confusing between the wiki, forums, and VirtualBox manual. The VirtualBox manual recommended installing dkms first, but the dkms package in AUR was flagged as out of date. I tried my luck with the instructions on the ArchWiki’s VirtualBox page instead; verify gcc and make are installed and
sh /media/cdrom/VBoxLinuxAdditions-x86.run. The wiki warned of “errors about init scripts and run levels and what not” but to my great surprise everything built and installed with nary a complaint.
I rebooted, and then shutdown. After the shutdown Arch wouldn’t start; it would switch resolution to 800x600 but get stuck there with a black screen. I rebooted in fallback mode, removed
vga=771 from /boot/grub/menu.lst and retried. Now that the boot process stayed in 640x480 I could see what was going wrong, although I little idea what it meant:
Code: Bad EIP value. EIP: [<00000000>] 0x0 SS:ESP 0068:c042fdf4 Kernel panic - not syncing: Fatal exception in interrupt
I guess someone doesn’t like zeroes. Restarted in fallback mode: same error this time! Normal mode: same error. Rebooted the EEE PC completely (this had helped previously with another VirtualBox problem): same error in both modes. I noted that there seemed to be some variation in when in the boot process the kernel panic occurred, although it was always very early. I had recently unplugged the EEE PC at which time it switched to its “Auto Power-Saving” mode with lower (and probably variable) clock speed. I speculated that maybe this mode was causing some random timing error (“not synching,” remember?) in the early bootup process. I changed to the “Super Performance” mode, rebooted Arch, and lo and behold, it worked! Once the boot was complete I switched back to the Auto Power-Saving mode.
I’ve had these kernel panics several times since. Also in Super Performance mode and with AC connected. They’re more frequent when power is disconnected and CPU throttled and I’ve rarely had two in a row with AC connected. I don’t think I had any of these before installing the VirtualBox Guest Additions.
Recommendation: Do not change the resolution of your fallback installation.
Recommendation: If you get kernel panics during bootup disable CPU throttling and if possible connect AC.
VirtualBox Guest Additions: Configuration
I added rc.vboxadd to /etc/rc.conf. During bootup the message
Starting VirtualBox host to guest time synchronization
is printed to the console which I presume means that rc.vboxadd-timesync is started by rc.vboxadd without having to be added individually to the daemons in /etc/rc.conf.
When shutting down Arch I noticed the error message:
/etc/rc.d/functions: line 167: /etc/rc.d/vboxadd-timesync: No such file or directory
The correct file name should be /etc/rc.d/rc.vboxadd-timesync. I tried to figure out what was the problem but wasn’t familiar enough with rc.d to be able to figure it out. In fact, I couldn’t even locate where the stop_daemon function where the error occured was called from.
Update 2009–02–20: Alan Savage figured this one out and submitted a patch for it.
/etc/rc.d/rc.vboxadd-timesync start (or
stop) from the command line resulted in:
/etc/rc.d/rc.vboxadd-timesync: line 226: begin: command not found
begin() function was indeed missing from the code block that defined functions for Arch so I copied the one from the Gentoo block and inserted it at line 169.
Update 2009–02–14: A better place to copy
begin() from is the Arch-specific definition in rc.vboxadd. I’ve submitted a patch for this to the vbox-dev mailing list.
Here are the contents of the xorg.conf file that VirtualBox Guest Additions installed:
# Default xorg.conf for Xorg 1.5+ without PCI_TXT_IDS_PATH enabled. # # This file was created by VirtualBox Additions installer as it # was unable to find any existing configuration file for X. Section "Device" Identifier "VirtualBox Video Card" Driver "vboxvideo" EndSection
My impression was that Xorg was supposed to use hal to discover the video modes that the “VirtualBox Video Card” supported, and that the X screen resolution would seamlessly follow the VirtualBox window size. This didn’t work for me and I was stuck with 640x480 with no other modes available according to xrandr. I had to add the following to /etc/xorg.conf to get additional resolutions:
Section "Screen" Identifier "Default Screen" Device "VirtualBox Video Card" SubSection "Display" Modes "1024x600" "800x600" "640x480" "1024x768" EndSubSection EndSection
(As an aside I also tried generating an xorg.conf using hwd but when it didn’t use the vboxvideo driver (opting instead for vesa) I didn’t pursue that avenue further.)
The only other problem I’ve had with Xorg is that switching modes with
Ctrl+Alt+Keyopad-Plus/Minus was unreliable at best at rendered the session unusable at worst. I disabled these keys with the
DontZoom option as described in the xorg.conf manpage:
Section "ServerFlags" Option "DontZoom" "true" # Disable mode-switching keys. EndSection
Instead I use xrandr to switch modes, e.g:
xrandr --output VBOX1 --mode 1024x768
I have set up aliases for this, e.g.:
alias 1024x768='xrandr --output VBOX1 --mode 1024x768'
It’s a wrap!
That pretty much sums it up. Most everything seems to be in working order now and it’s trivial to install additional software with pacman as needed. The one thing I know I’ll want to figure out sooner or later is how to how to “hotswap” keyboard layouts but I’m in no hurry.
I’m a long-time (as in since the Motorola 68030 and System 7 days) Mac user and currently own a PowerBook G4 going on it’s fifth year. However, I’ve been following the emergence of netbooks heralded by the EEE PC with a fair amount of interest and in November finally bought myself an EEE PC 900HA (which I may do a mini-review of some day).
I wasn’t thrilled by the prospect of having Windows XP on it but I do live with Windows everyday at work, and given that I spend most of my time in a web browser or terminal window I figured it wouldn’t matter too much. I also told myself I’d install Linux on it fairly immediately. Well, now it’s February. I’ve been putting off the Linux install, struggling along with Cygwin instead. I’d have to say the upside of this was that I’ve had two months to try out Google Chrome. My impression is that Google got a lot of things right and managed to streamline the browsing experience quite a bit; now I’m not at all so content with Firefox and Safari…
Anyway, back on topic, today I decided to take some time to get Linux on the EEE PC. I’ve been deliberating for some time which distro to use; on the one hand there’s Ubuntu which I imagine is friendly as can be and probably a great distro all over, on the other hand I’m eager to try using xmonad as my window manager and drawn towards choosing a similarly bare bones distro to run it on. I’ve finally settled on the latter with Arch Linux; the main selling points, in my perception, being:
- Excellent Haskell support.
- The rolling release system.
- The package system. I’ve had a good experience with MacPorts, and Arch Linux’s pacman/ABS appears to be similar.
- The bare-bonesiness. If nothing else I hope to learn quite a bit from installing and configuring Arch Linux. I also imagine that by limiting the installation to what I use and need there’ll be less noise and more signal when I inevitably have to trouble-shoot something.
I’m working my way through the installation process as I type, and it is indeed a rather arduous process. The Beginners Guide to installing and configuring Arch Linux prints to a hefty 53 pages, not counting the 18 page appendix.
Ouch! It would appear I just screwed up by hitting the ESC key at an inopportune moment in the installer (my motor memory must have thought I was in vi). This appears to have bypassed steps which the guide prefaces by repeated italicized notes regarding their importance. Oh well, I guess that’s as good an excuse as any to cut off this post early and go to bed.
At a later date I’ll comment in more detail on the installation experience; what confused me, what worked, and what didn’t.