A Chromebook… for $199

I picked up an Acer C720 Chromebook a few days ago to see what all the rage was about. After all, I spend most of my time in the browser already, where I create, read, update, and delete things. Do I really need all the excess of a full-fledged operating system? Can I get by with a $199 laptop that is cheap enough and light enough that I can take it traveling everywhere? I won’t go into details on the hardware – there are plenty of reviews already – but I did want to lay down some thoughts on the experience. I used Code Jam as a litmus test for Chromebooks as a simple development machine, and this is how it turned out:

  • This thing is fast. When I hear “Celeron”, I think machines made by Compaq or eMachines sitting next to CRTs that are dog-slow and will probably break in 3 months. This Celeron, however, is Haswell microarchitecture, and with minimal requirements of Chrome OS, makes the machine feel fast. It also helps that Chromebooks come with flash storage. This means excellent boot times (far faster than any Mac/Windows machine), and general snappiness.
  • This thing is light. It only has an 11″ screen, but compared to my unibody Macbook Pro 15″, it’s a much better travel companion. And the battery really does last all day (it’s rated for 8.5 hours, and that’s pretty much what I get).
  • The screen sucks. The TN panel has terrible viewing angles. The HP Chromebook 11 is the only budget Chromebook with an IPS display right now, but its processor is roughly half as fast.
  • Some things are really hard that are trivial on the conventional OS’s:
    • Try remapping the caps lock key to control on an external keyboard. In Chrome OS, you can easily do that with the internal keyboard, but not for external keyboards. It took me about two hours of reading through bug reports to find a hack.
    • Unzipping files – Chrome OS has built-in functionality that mounts zip files as ejectable drives – but it doesn’t work with all zip formats. For example, Code Jam solutions. The workaround for this was downloading and unzipping on my server and using a remote text editor to read the file.
    • Transferring files to/from remote servers – you can’t use TeamViewer (there’s no app), you can’t use SFTP (there’s an app but it costs money). In Code Jam, my workaround for the input/output files was copy and paste. Less than ideal.
  • Some issues are unique to the architecture of Chrome OS:
    • Flaky internet makes Chrome OS suck – you’re in some purgatory between good internet and no internet at all, which means that many apps are spinning around trying to connect rather than going into their (reduced functionality) offline modes.
    • The NaCl SSH client is sometimes insufficient. For example, Koding requires an SSH proxy server, and Chrome OS can’t do that. The workaround is to use Koding’s web terminal interface.
  • And some issues are just because Chrome OS is younger and not as polished:
    • I had frequent bluetooth disconnects for my headset and mouse. For my headset, the only solution was often to reboot (resetting the bluetooth power didn’t help).
    • While you can set “natural scrolling” for the trackpad, you can’t for an external mouse.
    • Scrolling with a bluetooth mouse was often quite jumpy scrolling pages at a time, even at the lowest sensitivity settings.
  • But it does work. My Code Jam “stack” consisted of a Koding VM and a Zed text editor client on Chrome set up to work with remote files on the VM. Pretty simple, and it worked pretty well (aside from the occasional Zed save hiccups that didn’t push the last character I typed).

Ultimately, this Chromebook is not something that I’d want as a development replacement machine. Chrome OS is just a wee bit too limiting. I sorely miss some of the niceties I have on Mac OS X – TotalTerminal, Alfred, Transmit, and Adium to name a few. Maybe in a few months we’ll see Haswell+ Chromebooks with an IPS display, and I’ll have a nice travel companion (assuming where I travel to has good internet).

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Compiling rippled on Ubuntu

There are instructions for compiling rippled on Ubuntu, but they’re not entirely clear. Sometimes you just want a script to do everything for you. Here’s something I cobbled together for Ubuntu 12.04 (you may want to modify the tag for whatever the current release of rippled is):

#!/bin/bash
set -e
sudo apt-get update; sudo apt-get -y upgrade
sudo apt-get install -y git scons ctags pkg-config protobuf-compiler libprotobuf-dev libssl-dev python-software-properties
sudo apt-add-repository -y ppa:boost-latest/ppa
sudo apt-get update
sudo apt-get install -y libboost1.55-all-dev
git clone https://github.com/ripple/rippled.git
cd rippled
git checkout tags/0.23.0
sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install -y gcc-4.8 g++-4.8
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.6 60 --slave /usr/bin/g++ g++ /usr/bin/g++-4.6
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 40 --slave /usr/bin/g++ g++ /usr/bin/g++-4.8
sudo update-alternatives --set gcc /usr/bin/gcc-4.8
scons

Alternatively, you can just pull down the binary I compiled and install the associated dependencies:

#!/bin/bash
set -e
sudo apt-get update; sudo apt-get -y upgrade
sudo apt-get install -y protobuf-compiler libprotobuf7 python-software-properties
sudo apt-add-repository -y ppa:boost-latest/ppa
sudo apt-get update
sudo apt-get install -y libboost1.55-all
sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install -y gcc-4.8 g++-4.8
curl -O "https://secure.dustin.li/rippled/rippled"
chmod +x rippled
./rippled -u

Someone also submitted a package to Debian, but that will take a while to trickle downstream.

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Seagate 2TB Backup Plus Portable Drive disassembly

Seagate has developed a new 2.5″ laptop drive with a 2 TB capacity. Previous 2 TB laptop drives had a thickness of 15 mm, making them unsuitable for placement in most laptops. In contrast, the new Seagate/Samsung Spinpoint M9T ST2000LM003 (HN-M201RAD/AVN) has a thickness of only 9.5mm. However, this drive is not yet being sold through normal consumer sales channels. However, these drives are being sold as part of the Seagate Backup Plus line, inside a nice little USB 3.0 enclosure. These Backup Plus drives are also much cheaper (about 50% less) than the drives on eBay (step 3: profit?). Note, however, that you get no warranty (Seagate warranty validation: “The product you identified was sold as a system component”). The only tricky part is actually getting the drive out of the enclosure, especially if you’re trying not to damage the case.

The top of the case is made of stamped metal, and is held on by a combination of double sided tape and small clips.

Top of Seagate Backup Plus case

Because there is more tape near the USB plug, it is easiest to begin prying the case off from the other end. Start by jamming something thin under the edge of the top of the case (see photo below). To avoid damage, you’ll probably want to use a nylon spudger (while screwdrivers work fine they will probably cause some cosmetic damage to the case). You can slide the spudger around the edge of the case, releasing the two clips at the end.

Spudger in Seagate Backup Plus Portable Drive

I ended up jamming the spudger further into the top of the case (on top of the hard drive) and prying gently, which also released two of the side clips (but being careful not to deform to the top too much).

Samsung Backup Plus - clips released

After that, you just have to work the spudger around releasing the rest of the clips, and the top will come off. The drive itself is held into the bottom part of the case by two plastic pegs that protrude slightly from the case into the screw holes of the drive on the side away from the USB plug. They can be easily released with a little gentle prying.

Seagate Backup Plus - bottom case

Success! A 2TB internal laptop drive at last!

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Backporting packages – bandwidthd on Precise

bandwidthd is a great tool to graph traffic on your network interfaces, especially when you’re acting as an ISP for the better part of the city. Unfortunately, bandwidthd on Ubuntu Precise Pangolin (12.04) stopped getting updated at 2.0.1+cvs20090917-4.1. This package contains a pretty serious bug that causes bandwidthd to lose all data every 6 hours or so. Fortunately, there’s a more recent package (2.0.1+cvs20090917-5) with the fix committed, but it’s only available for Ubuntu 12.10+. (NB: 2.0.1+cvs20090917-7 has a dependency on a higher version of Apache than 12.04 has, so we’re ignoring it.) Solution: backport! (Here’s a dpkg that you can just dpkg -i if you don’t want to do it yourself.)

It’s actually not very difficult to do a backport, but it’s not trivial the find the correct instructions.

  • Grab all sources from LaunchPad: .orig.tar.gz, .debian.tar.gz, .dsc
  • dpkg-source -x *.dsc
    cd bandwidthd-2.0.1+cvs20090917
    dpkg-buildpackage -rfakeroot -uc -b
    cd ..
    dpkg -i bandwidthd_2.0.1+cvs20090917-5_amd64.deb
  • Done!

You will probably also need to install build dependencies, but just apt-get whatever you need.

This could potentially all be automated with backportpackage, but I haven’t investigated yet.

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Getting Kali Linux on a Cubieboard

Here’s an abbreviated tutorial for getting Kali Linux (1.0ish) running on a Cubieboard. (In case you’re wondering, Kali is the successor to BackTrack.) I use Berryboot as the bootloader, which allows us to multiboot and use compressed file systems (>50% compression, saving ~2 GB for a full install of Kali), and also makes it easy to swap around and play with different operating systems.

Installing the quick and dirty way

Do step 1 below.

Download one of these:

Now skip to step 10 below.

Installing the dirtier way

What you’ll need: a USB flash drive (~4 GB), Debian/Ubuntu Linux (e.g. Kali on VMware works great).

  1. Begin by installing Berryboot onto a microSD card. The easiest way is to empty the microSD slot, boot into the built-in Android system on the Cubieboard NAND, download the Berryboot APK, and follow the instructions.
  2. Install some tools on your Linux box:
    apt-get -y install squashfs-tools kpartx
  3. Now we need to build a squashfs image of the rootfs that Berryboot can boot form. We’ll do this the easy way: by modifying the Kali Raspberry Pi image. Download the image onto your Linux box (you do have a Linux box, don’t you?):
    curl -O "http://cdimage.kali.org/kali-images/kali-linux-1.0-armel-raspberrypi.img.gz"
  4. Unzip the Kali Raspberry Pi image:
    gunzip kali-linux-1.0-armel-raspberrypi.img.gz
  5. Mount the image:
    kpartx -av kali-linux-1.0-armel-raspberrypi.img
    mount /dev/mapper/loop0p2 /mnt
  6. Modify the mount point:
    sed -i 's/^\/dev\/mmcblk/#\0/g' /mnt/etc/fstab
  7. We need to configure the kernel modules that will be loaded. Note that Berryboot ships its own kernel modules, so we don’t need the actual blobs themselves. Create or overwrite these files (these are borrowed from the Cubieboard hwpack):
    /mnt/etc/modules:

    # /etc/modules: kernel modules to load at boot time.
    #
    # This file contains the names of kernel modules that should be loaded
    # at boot time, one per line. Lines beginning with "#" are ignored.
    
    #For SATA Support
    sw_ahci_platform
    
    #Display and GPU
    lcd
    hdmi
    ump
    disp
    mali
    mali_drm
    8192cu

    /mnt/etc/modprobe.d/8192cu.conf:

    # Workaround for dropping connections because power save
    options 8192cu rtw_power_mgnt=0 rtw_enusbss=0
  8. Now we need to package up the rootfs we customized into a squashfs image:
    mksquashfs /mnt ~/kali-on-cubie.img -comp lzo -e lib/modules
  9. Clean up:
    umount /mnt
    kpartx -d kali-linux-1.0-armel-raspberrypi.img
  10. Now we need to get the image onto the microSD card so that Berryboot can use it. Copy your new image (kali-on-cubie.img) to a USB flash drive.
  11. Boot your Cubieboard with Berryboot (i.e. the microSD card inserted). Click “Edit Menu”. Click (and hold) “Add OS”, and you’ll get a dropdown menu; select “Install from USB stick”, and choose the kali-on-cubie.img we just created.
  12. Close the menu editor. Boot Kali.
  13. Eat cake to celebrate.

Installing the unicycle caving way

Instead of using the prebuilt ARM image for Raspberry Pi, we’ll build the rootfs “from scratch” (kind of). This lets us use the armhf architecture, which Google tells me is better than armel (Cubieboard has a more modern processor that supports the faster armhf instructions, whereas Raspberry Pi only supports armel). Also, we can customize the image, leaving out packages which we might not need in a memory/storage constrained environment.

Basically, all we need to do is to build the rootfs following the instructions that are conveniently laid out in the Kali docs. For posterity, I preserve the scripts below.

After building the rootfs, we resume at step 6 above, of course substituting the actual path of our new rootfs for /mnt (which is the path of the rootfs that would have been mounted from the prebuilt image).

apt-get install debootstrap qemu-user-static

# define which packages you want here. If you want everything, add "kali-linux-full". See also this kali.list.chroot for ideas.
export packages="xfce4 kali-menu wpasupplicant kali-defaults initramfs-tools uboot-mkimage nmap openssh-server"
export architecture="armhf"

cd ~
mkdir -p arm-stuff
cd arm-stuff/
mkdir -p kernel
mkdir -p rootfs
cd rootfs

debootstrap --foreign --arch $architecture kali kali-$architecture http://archive.kali.org/kali
cp /usr/bin/qemu-arm-static kali-$architecture/usr/bin/

cd ~/arm-stuff/rootfs
LANG=C chroot kali-$architecture /debootstrap/debootstrap --second-stage

cat << EOF > kali-$architecture/etc/apt/sources.list
deb http://http.kali.org/kali kali main contrib non-free
deb http://security.kali.org/kali-security kali/updates main contrib non-free
EOF

echo "kali" > kali-$architecture/etc/hostname

cat << EOF > kali-$architecture/etc/network/interfaces
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
EOF

cat << EOF > kali-$architecture/etc/resolv.conf
nameserver 8.8.8.8
EOF

export MALLOC_CHECK_=0 # workaround for LP: #520465
export LC_ALL=C
export DEBIAN_FRONTEND=noninteractive

mount -t proc proc kali-$architecture/proc
mount -o bind /dev/ kali-$architecture/dev/
mount -o bind /dev/pts kali-$architecture/dev/pts

cat << EOF > kali-$architecture/debconf.set
console-common console-data/keymap/policy select Select keymap from full list
console-common console-data/keymap/full select en-latin1-nodeadkeys
EOF

cat << EOF > kali-$architecture/third-stage
#!/bin/bash
dpkg-divert --add --local --divert /usr/sbin/invoke-rc.d.chroot --rename /usr/sbin/invoke-rc.d
cp /bin/true /usr/sbin/invoke-rc.d

apt-get update
apt-get install locales-all
#locale-gen en_US.UTF-8

debconf-set-selections /debconf.set
rm -f /debconf.set
apt-get update
apt-get -y install git-core binutils ca-certificates initramfs-tools uboot-mkimage
apt-get -y install locales console-common less nano git
echo "root:toor" | chpasswd
sed -i -e 's/KERNEL\!=\"eth\*|/KERNEL\!=\"/' /lib/udev/rules.d/75-persistent-net-generator.rules
rm -f /etc/udev/rules.d/70-persistent-net.rules
apt-get --yes --force-yes install $packages

rm -f /usr/sbin/invoke-rc.d
dpkg-divert --remove --rename /usr/sbin/invoke-rc.d

rm -f /third-stage
EOF

chmod +x kali-$architecture/third-stage
LANG=C chroot kali-$architecture /third-stage

cat << EOF > kali-$architecture/cleanup
#!/bin/bash
rm -rf /root/.bash_history
apt-get update
apt-get clean
rm -f cleanup
EOF

chmod +x kali-$architecture/cleanup
LANG=C chroot kali-$architecture /cleanup

umount kali-$architecture/proc
umount kali-$architecture/dev/pts
umount kali-$architecture/dev/

cd ..

These instructions were adapted from BerryBoot’s docs.

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MagTool is now open source!

MagTool, my erstwhile magnetic stripe project, is now open source. Go forth and fork. =)

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HBS-700 sound quality on Mac OS X

I was recently looking for a pair of Bluetooth headphones to isolate myself from the world without a cord tethering me to my laptop. I ended up settling on LG’s HBS-700 headphones due to spectacular reviews on Amazon. The cost of selecting the HBS-700, rather than its newer cousin, the HBS-730, was missing out on the apt-X codec, which is reportedly much better than the standard SBC codec that most Bluetooth devices use. But the HBS-730 noted terrible range and poor reliability, which really doesn’t work for me when I’m shipping these headphones 12 timezones away from the retailer. So I chose the HBS-700.

Despite the occasional typo in the user manual (yes, I do read user manuals for fun), first impressions of the device were pretty good. The device is light, well-built, and comes with a charge. The only problem I noticed was that sound quality was substantially lower than my cheapo Acoustic Research ARE-09s. Turns out that there is an easy fix for this; disconnect the headset, open Terminal and run this:

defaults write com.apple.BluetoothAudioAgent "Apple Bitpool Min (editable)" 53

For the HBS-700, 53 is the highest bitpool supported. By default my headset had previously negotiated a much lower bitpool, which corresponds a much lower bitrate. Interestingly, setting the minimum bitpool to 51 actually resulted in worse performance, because of the mismatch of sampling rates between the encoded audio I was listening to (at 48 kHz) and the SBC encoding (at 44.1 kHz). You can examine the negotiated bitrate using this command:

defaults read com.apple.BluetoothAudioAgent

According to the A2DP specs you can get a rough idea of how bitpools correspond to bitrates using the following table:

Table 4.7: Recommended sets of SBC parameters in the SRC device
SBC encoder settings* Middle Quality High Quality
Mono Joint Stereo Mono Joint Stereo
Sampling frequency (kHz)
44.1 48 44.1 48 44.1 48 44.1 48
Bitpool value
19 18 35 33 31 29 53 51
Resulting frame length (bytes)
46 44 83 79 70 66 119 115
Resulting bit rate (kb/s)
127 132 229 237 193 198 328 345
*Other settings: Block length = 16, Allocation method = Loudness, Subbands = 8

Happy listening!

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A theory about UAE’s internet connectivity

Ever wondered why internet in the UAE sucks? I have a theory…

  1. Etisalat runs a Great Firewall of UAE for HTTP traffic, and is overloaded and/or buggy.
  2. Commonly accessed files are sometimes cached by the Great Firewall, and can be delivered/inspected/passed through quickly. However, less common files need to be fetched by the Great Firewall before being delivered to the end user. Because the Great Firewall is overloaded or buggy, it can sometimes inspect and deliver the first bytes of a file quickly before slowing to a crawl. For example, this could manifest as downloading a file at 300 KBps for a few seconds before dropping down to 50 KBps for the remainder of the file, or producing a sawtooth-like bandwidth graph. If it’s a large file, it could end up taking hours. Sometimes the Great Firewall is unable to do any caching due to cache settings on the web server, in which case it has to inspect the file each time it is downloaded (you will see this with the results from speedtest.net).
  3. Encrypted data cannot be inspected and seems to be ignored by the Great Firewall. This suggests a few ways around the firewall: the most commonly used one is to VPN out. Another way is to use HTTPS. This is particularly useful with Google Maps, for example (http://maps.google.com/ vs. https://maps.google.com/). You can also see a pronounced difference when using Speedtest over an encrypted connection or not (https://dustin.li/tmp/st/ vs. http://dustin.li/tmp/st/ - this is my server in North Virginia). In my own testing, direct encrypted (e.g. HTTPS) connections outperform VPN encrypted connections, which in turn outperform unencrypted HTTP connections. We’re talking almost an order of magnitude – 4.83 Mbps HTTPS vs. 0.64 Mbps HTTP.
  4. Etisalat’s DNS service occasionally slows to a crawl, which introduces non-bandwidth related latency. I have sometimes worked around this when I am at home by switching to Google’s DNS servers or my personal DNS server.
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UMNR 2012

We’re organizing the 1st UAE Meeting on Neurorehabilitation (UMNR) here at Khalifa University! Come hang out with all the cool people. It’s on March 9-10, 2011.

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Scooba: meh

After correcting a minor incident of exploding capacitors, I was able to charge my Scooba 330 and set it free on the tile floors of my new apartment. In short: meh. While it’s really cool from a geeky perspective, it just doesn’t do a great job. For example, it gets stuck on the transition from the tile to the marble. It doesn’t do a good job sucking the water back up (probably a defect/maintenance issue), leaving behind puddles as if someone had cleaned the floor with a dripping mop, getting an optimistic 30% of the water it layed down. It doesn’t self dock, requiring you to manually plug it in every time. It doesn’t do a great job of picking up hair off the floor. It looses traction quite a bit. There are no infrared sensors on its bumpers, causing it to slam into things at full speed. Its bumpers aren’t terribly sensitive, making it bash into things and spin its wheels, not realizing that it’s not moving. It requires maintenance of the brushes, vacuum port, and filter after every cleaning, and rinsing of both the dirty and clean tanks. I’ll keep using it because I’d never mop my own floors, but they could do much better… iRobot has released an updated Scooba but the reviews are also universally “meh”. In comparison, my Roomba 535 is awesome – requires almost no maintenance, and always gets back to its docking station on its own.

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