Sunday, March 17, 2013

Chromebook Tips, Tricks & Errata

1. If, like me, you ever choose to clone partitions from your SSD/HDD to external media and then boot from that media - you'll swear someone slipped a hallucinogen into your coffee!  Be sure to complete the process by assigning the clone a new UUID like this:
$ sudo cgpt add -i 3 -u $(uuidgen) /dev/sdb
and avoid taking the trip to Wonderland all together.


2. To identify the current rootfs & kernel partitions: 
$ rootdev -s
will return the partition mounted as / like this:
where # is 3, 5, or 7. So, just subtract 1 from # to identify the current kernel partition.


3. Interestingly, the Acer C7 seems unable to boot from an SD card in the on-board card reader.  I have successfully created bootable SD cards using the slot, but must move them to an external USB reader to boot from them.  The only conclusion I can draw is that the firmware can only boot from a device connected via USB and that the card reader slot is, in fact,  not USB.


4. To fix the erratic trackpad behavior in Ubuntu:

sudo gedit /usr/share/X11/xorg.conf.d/50-synaptics.conf

after MatchIsTouchPad "on" in the file, insert these lines:

Option "FingerLow" "4"
Option "FingerHigh" "10"

Reboot and the problem should be resolved.  However, it's possible that a system upgrade (i.e. 12.04 to 12.10) may wipe out this change, so keep that in mind.


5. Another factor to consider regarding Linux Distros on Chromebooks is the version of kernel that the distro ships with.  Since Google's current CrOS kernel is version 3.4.0, I've generally stuck to distros that included kernel 3.4.0 or earlier.  While the CrOS kernel apparently incorporates some features of later kernels, for optimal compatibility, 3.4.0 seems like a good logical target.

Postscript - 05/30/13 - Just ran across this excellent explanation of the issue:
I was merely speculating based on reasoning and experience.


  1. Hi. I've been running Ubuntu on my Acer C7 since March myself, and I have a seemingly uniqe problem with my trackpad. It works perfectly all the time, except in bright light. Especially under fluorescent light. I've tried the fix listed here, and I've tried changing the sensitivity settings in Ubuntu, but no change. This is the ONLY thing keeping me from using Ubuntu full-time on my chromebook. Have you heard of this before?

    1. I think so - I seem to recall someone describing such a problem on the ChrUbuntu blog & they may have decided that it had something to do with grounding (electrical). But, I abandoned that ship months ago & these days my memory is about as reliable as Windows 95.

    2. OK, thanks for your reply. I'm going to try the Crouton route because this is irritating.

    3. I understand. I don't know if the trackpad issues exist in a chroot or not, since I haven't spent much time there. However, I can tell you the issues DO exist with other distros and that, at least once, the fix I describe here did not work.

      Crouton requires a substantial STATEful partition (#1) for Ubuntu, so you might need to shift some space back to it. Good luck!

    4. The fluorescent/bright light scenario makes no sense, unless the light in question is sending out crazy amounts of electrical interference. Still, I'd suspect it to affect the monitor before the trackpad...

      Having said that, I'm having my own unique trackpad issues. The main issue is two-finger scrolling. It's mostly unresponsive unless I touch the laptop body or port with my other hand. I've demonstrated this constantly with my unit and my wife's identical Acer C7.

      To ratchet up the maddening factor, my laptop worked fine when plugged in to the adapter, hers did not.

      Also, mine appeared to be fixed after I installed extra RAM. Installing extra on the wife's had no effect. But mine is now back to its original state of malfunction after upgrading from 12.04 to 12.10.

    5. That's why we call it "erratic behavior," because it doesn't seem to make sense (in contrast with consistant behavior.) That usually only means that the cause is obscure.

      Does the issue occur in Chrome OS? If not, then logically, either the problem isn't hardware or it can be corrected in software.