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.

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.

In the past, I’ve used unetbootin to create bootable USB keys. When I did this with the Linux Mint 9 ISO image, the resulting USB key booted up just fine, but the installer application hung when trying to run the partition editor. I narrowed this down to an assertion failure in libparted. Apparently it doesn’t like the geometry on some USB keys. This is a known bug.

Fortunately, the ThinkPad R61 has a CD drive, so I created a CD from the ISO image and booted that. Then after installing Mint 9 on the hard disk and booting that, I was able to create a bootable USB key that didn’t crap out in the installer. I did this by using Mint 9’s built-in Startup Disk Creator, which is in the main Menu under Administration. I told it to erase the entire USB key, which apparently reconfigured its partition table into a form that libparted liked. I verified this by rebooting the R61 with the USB key and running gparted.

The next set of problems came when I tried booting an older ThinkPad R50p with the USB key. As in all recent ThinkPads, you can choose the boot device by pressing the blue ThinkVantage or Access IBM button at startup, then pressing F12. But on the R50p, the USB key wasn’t shown as a boot device. I ran Setup (IBM’s term for BIOS configuration), and in the Startup screen I tried to enable the USB HDD device. This didn’t work; the machine just beeped at me. After a long bout of head-scratching, I finally figured out that Setup doesn’t allow more than eight boot devices to be enabled. I disabled a couple of useless boot devices (e.g., HDD1 and USB Floppy), and then I could enable the USB key.

Finally the USB key would start to boot on the R50p. But after the Linux Mint logo came up, the machine hung with the hard disk light on solid. I rebooted from the USB key and selected the recovery mode boot option in Grub (I forget the exact name for it). Then I was able to see the last error message at the hang. It was an I/O error accessing the fd0 device, which is the floppy. More headscratching and Google searching revealed that I needed to disable the floppy device in Setup.

Now I was able to get past the hang on booting from the USB key, but then X refused to run, displaying a dialog box saying that it was going to run in low graphics mode. This turned out to be a problem with the kernel mode setting (KMS) feature of recent Ubuntu releases. Apparently this is a very bleeding-edge method of determining graphics card type, and it doesn’t appear to work on older machines. The fix was to provide the nomodeset kernel parameter when booting. I did this by hitting Enter when the Grub menu came up, then hitting Enter again to edit the kernel command line. I add the nomodeset parameter and pressed Enter a couple of more times to boot. This time the system was able to boot to a good desktop, though the Mint logo didn’t appear during the early boot stages.

The solution is to download and build the HP printer package (known as hplip) from source. The complete instructions are here. I had to install the following extra packages before the configure and make steps would succeed: libjpeg-dev, libsnmp-dev, libcups2-dev, libusb-dev, python-dev, libsane-dev, and libcupsimage2-dev.

sudo modprobe visor

But when I switched to a different laptop running Linux Mint 7, pilot-xfer never seemed to be able to connect with the Centro for the second and subsequent attempts after a reboot. Some poking around revealed that the problem is apparently due to the visor module setting up an incorrect symbolic link for the device /dev/pilot. Normally, after you connect the Centro to the computer with a USB cable and press the hotsync button, /dev/pilot should become a symlink that points to ttyUSB1. But I was seeing it point to ttyUSB0, which is the wrong device file for the Centro.

I couldn’t find an elegant way to fix the problem, so I was forced to come up with a brute force method: before connecting the Centro with the USB cable, remove the visor module and the device symlink:

sudo rmmod visor
sudo rm /dev/pilot

Then after connecting the Centro, load the visor module again:

sudo modprobe visor

Note 1: Immediately after you load the visor module, /dev/pilot will point to ttyUSB0. That’s OK. After you press the hotsync button, the visor module should change the symlink to point to ttyUSB1. If it doesn’t, you’ll have to use the brute force “unplug and unload” method I described above.

Note 2: You should always press the hotsync button on the Centro before running pilot-xfer.

Note 3: You can eliminate the need to use the -p option with pilot-xfer by setting the environment variable PILOTPORT to /dev/pilot. Putting this line in your ~/.bashrc (if your shell is bash) will do the trick:

export PILOTPORT=/dev/pilot

To get started with maildrop on Linux Mint or Ubuntu, install the maildrop and courier-authdaemon packages. It’s not strictly necessary, but for safety you can also disable postfix by doing this:

sudo service postfix stop
sudo chkconfig postfix off

Now you need to configure fetchmail to use maildrop. Simply add the following line to your ~.fetchmailrc:

mda "/usr/bin/maildrop"

The quotes aren’t necessary; I had them there because I had been experimenting with passing options to maildrop. The fetchmail man page recommends the options “-d %T”, but these aren’t required in this simple, single-user setup.

The next step is to write some mail filtering rules for maildrop. These go into the file ~/.mailfilter. The mailfilter man page describes the filtering language, but doesn’t give many examples. Here’s my ~/.mailfilter (with a bogus address replacing a real one):

DEFAULT="$HOME/Maildir/inbox"
LINUS="$HOME/Maildir/linus"
WOTD="$HOME/Maildir/wotd"

logfile "$HOME/maildrop.log"

if (/^From:.*torvalds@linux\.com/)
{
  to $LINUS
}

if (/^From:.*word@m-w\.com/)
{
  to $WOTD
}

to $DEFAULT

In this example, I’m filtering mail to three different maildir directories; all messages that aren’t caught by the two filters get delivered to the default maildir. If these directories didn’t already exist, they would need to be created with the maildirmake program. maildrop also allows delivering mail to mbox files, but I consider mbox evil and don’t use it any more.

Now whenever you run fetchmail, it should hand off the mail to maildrop for delivery. Check the log file, ~/maildrop.log, to make sure your filtering works as expected.

fetchmail: connection to localhost:smtp [::1/25] failed: Connection refused.


The error was caused by fetchmail attempting to make an IPV6 connection to postfix on the local machine. Postfix refused the connection, so fetchmail then attempted an IPV4 connection, which was successful. The mail was delivered, but the error message was annoying.

As usual, I tried several solutions I found with Google, including an attempt to disable IPV6 on a system-wide basis. The thing that finally worked was to comment out the following line in /etc/hosts:

#::1 localhost ip6-localhost ip6-loopback


The problem isn’t fixed by making bash the login shell for a particular user, because some programs (such as Ruby) invoke /bin/sh, which is a symlink to /bin/dash. The fix for this problem is to make bash the default shell on a system-wide basis. The following command does that:

sudo dpkg-reconfigure dash

When you are asked whether to install dash as /bin/sh, answer No. This will update the symlink, among other things.

First, install the Microsoft TrueType fonts:

sudo aptitude install msttcorefonts

Then, if you are using an LCD monitor (e.g., a laptop), enable anti-aliasing (smoothing). On Linux Mint, start the Control Center from the main menu, then select Appearance. (On Ubuntu, I believe this is done using System > Preferences > Appearance.) Click the Font tab, and under Rendering, select Subpixel Smoothing.

You’ll see an immediate change in all fonts used in Gnome, but you may need to restart Firefox get it to see the new fonts and use smoothing.

One of the things I wanted to do with the V30 was scan books and convert them to plain text (for personal use; I’m not a pirate). For this I used Tesseract, an open-source OCR package that was developed at HP in the 90s and is now being maintained by Google. (The package name in Mint / Ubuntu is “tesseract-ocr”.) This program has a slightly funky command line interface (only reads TIFF files; the input filename must end in “.tif”, not “.tiff” or anything else; the output filename must be given without an extension). But it works surprisingly well, and I was able to integrate it into xsane (a decent scan utility) by writing a wrapper shell script that makes its command line interface identical to the gocr program that xsane uses by default.

I experimented with varying the dots per inch when scanning a book, to see how that affected tesseract’s error rate. At 100 DPI, the output was gibberish. At 200 DPI, the output was nearly perfect, with only about four errors per page that needed to be corrected manually. At 300 DPI, the output was marginally better, with perhaps one or two fewer errors per page. As I mentioned, this seems remarkably good. After I scan a page and convert it to text, I’ll fix the obvious errors and remove any end-of-line hyphenation. Then I’ll run aspell on the text to find additional errors. The most common errors are missing spaces (”ofthe”) and “l” change to “1″.

Another approach to OCR is to buy the commercial, closed-source Vuescan. I owned a copy six years ago, when xsane was not quite up to snuff, and it worked beautifully. I’m trying the latest trial version, and it has a number of improvements. The most interesting new feature is the integration of tesseract-ocr. This saves several steps in the process of scanning text, and the speed-up may be worth the price.