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The new Amazon Kindle app for Android stores its books in the “kindle” directory on the phone’s SD card. I naively assumed that I could copy any non-Amazon but Kindle-compatible books into that directory and have the app recognize them. I tried this with a mobipocket Jane Austen collection (a .prc file) that works just fine on the Kindle, but the Android app crashed immediately after display the book’s title and author.

The trick to getting such a book to be recognized on Android is to use Amazon’s free personal documents service to convert the file to a DRM-ified .azw file.

First, I emailed the .prc file as an attachment to my free personal documents email address: EXAMPLE@free.kindle.com (obviously, you must replace EXAMPLE with your configured Kindle email address). Within a few minutes Amazon converted the file to a .azw (DRM-ified version of the original file), and replied with an email that included a download link for the converted file.

I saved the file to a temporary directory on my computer and renamed it by changing the .azw extension back to .prc. This renaming is very important; otherwise, the Android app won’t recognize the file.

Finally, I copied the file to the kindle directory on the phone’s SD card. The Kindle app can see the file and display its contents.

It looks like the upgrade to the latest Ubuntu is going to keep me busy solving problems for a while.

Today’s second problem has to do with the fingerprint reader in the ThinkPad X41. There’s a good source of information here, but there wasn’t a definitive set of instructions for Ubuntu 10.04 that actually worked. Most of the uproar about the fingerprint reader in Ubuntu 10.04 has to do with a bug where the Enter key has to be pressed after swiping your finger. I couldn’t even get to that point; the trouble was getting logins to prompt for a finger swipe.

As per the instructions at ThinkWiki, I installed and configured the required packages from the standard repository (no PPAs):

sudo apt-get install thinkfinger-tools libpam-thinkfinger
sudo /usr/lib/pam-thinkfinger/pam-thinkfinger-enable

Then I was able to use tf-tool --acquire and tf-tool --verify to show that the fingerprint device worked. But I was not able to use tf-tool --add-user USERNAME to create a fingerprint file for use by the authentication system; this build of tf-tool did not support that option. So I had to set things up manually, by acquiring the fingerprint file and placing it in the proper directory, with the proper name, and with the proper permissions:

sudo su    # login as root
cd /etc/pam_thinkfinger
tf-tool --acquire USERNAME.bir
chown USERNAME:root USERNAME.bir
chmod 400 USERNAME.bir

In all of these commands, substitute your ordinary user name for USERNAME. After this is done, authentication prompts, either in a terminal (e.g., with sudo) or in X (e.g., the login screen), should ask for either a password or a finger swipe. Due the known aforementioned bug, it may also be necessary to hit Enter after the swipe.

I have an old Logitech QuickCam for Notebooks that uses the pwc (Philips Web Cam) driver on Linux. This camera has always worked flawlessly on Linux Mint 6 (Ubuntu 8.10). But on Linux Mint 9, the camera only worked the first time it was plugged in; on subsequent plug-ins, no programs could read images from the camera. The fswebcam utility reported a timeout trying to read the frame buffer; other programs like Cheese or Skype simply displayed blank images.

The solution is to unplug the camera (if it is not already unplugged), then forcibly remove the pwc driver:

sudo modprobe -r pwc

Then the next time the camera is plugged in, the pwc driver will be loaded automatically and will work properly. This has to be done every time you unplug the camera. I’m not sure why this is necessary with recent Ubuntu releases.

My employer’s VPN system doesn’t allow more than one login at a time. But there are occasions when I’d like to be able to use the VPN from two different laptops simultaneously. The solution, most of which I found here, is to use iptables on the machine running the VPN to forward packets from the machine not running the VPN.

In my case, the Juniper VPN software (ncsvc) sets up a connection on the net device tun0, and the network address is 10.0.0.0. So after I start the VPN on one machine, I run the following script on that machine:

#!/bin/sh
# Share the VPN connection with other machines on the local net.
# The assumption here is the the VPN network is 10.0.0.0.
if [ `id -u` -ne 0 ] ; then
   echo "You are not root.  Rerunning with sudo..."
   sudo $0
else
   echo "1" > /proc/sys/net/ipv4/ip_forward
   iptables -A FORWARD -i eth0 -d 10.0.0.0/8 -j ACCEPT
   iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE
   sysctl net.netfilter.nf_conntrack_acct=1
fi

Be sure to replace the network address (10.0.0.0), VPN net device (tun0) and local net device (eth0) with the correct values for your system.

Then on the machine that is not running the VPN, I run the following script:

#!/bin/sh
sudo route add -net 10.0.0.0 netmask 255.0.0.0 gw VPNHOST
sudo cp /etc/resolv.conf.vpn /etc/resolv.conf

In this script, replace VPNHOST with the hostname of the machine that is running the VPN (i.e., the name of the machine that is running the first script above). I use static IP addresses on all of my machines, and have added entries for these addresses to /etc/hosts on all machines. I’m not sure how this would work with dynamic IP addresses (DHCP).

The last line of this script is the one new thing I’m doing differently from the scripts at the aforementioned link. It makes the non-VPN machine’s name resolution configuration file identical to that of the VPN machine. This allows the non-VPN machine to resolve hostnames residing on the VPN. In order for this to work, I had earlier copied /etc/resolv.conf from the machine running the VPN to the non-VPN machine, and renamed it to /etc/resolv.conf.vpn.