The NSLU2 causing trouble recently...

We've had two serious bugs on the NSLU2 recently that both caused the system not too boot anymore. The first one was related to initramfs-tools. Kevin Price reported that after upgrading to initramfs-tools 0.92 the system would hang during boot waiting for the root filesystem. When I booted my NSLU2 and looked at the output, I noticed that no root device was set. When I mentioned this to maks, the maintainer of the initramfs-tools package, he immediately knew what was wrong and uploaded a fix. On the NSLU2, the boot loader doesn't pass a root device to the kernel so we set one in the initramfs itself. The code that loads this config variable is not used by many devices so nobody noticed that this got broken in 0.92 until the package moved to testing.

The second problem, reported on Saturday by Paul Collins and diagnosed today with some help from Kevin Price is also related to the strange way the NSLU2 boots. The NSLU2 has 6 MB available for the ramdisk but due to a bug in APEX (the second stage loader used on the NSLU2 by Debian) only 4 MB are actually used. When you write a ramdisk that is larger than 4 MB but smaller than 6 MB, flash-kernel will happily write the full image, but APEX will only tell the kernel about the first 4 MB. As it turns out, everything works fine on arm with 2.6.25, but on armel some additional SCSI modules are enabled that result in the ramdisk becoming too large. The short term solution is to disable these modules, but really APEX should finally be fixed (patches have been available for quite a while thanks to Gordon Farquharson). Fortunately 2.6.25 hasn't moved to testing yet and this problem only occurs on armel, so few people were impacted.

The nice thing about the NSLU2 is that you can write a new flash image via the network, so you can flash a good image in case your machine no longer boots. Nevertheless, we have to make sure such serious bugs don't occur in the future or that they are at least caught very early. Special thanks go to testers like Kevin Price.

Installer finally working again on Linksys NSLU2

The release release team of Debian released 4.0r2 today which fixes the bug that kept the installer from working on ARM based systems, such as the Linksys NSLU2. This means that installations are finally possible again. I've updated my installation instructions accordingly.

I've also updated the tar ball used for the manual installation to 4.0r2 but I doubt many people are interested in this method now that the installer is working again.

Tips on reducing memory and running Linux on a flash device

David Härdeman has contributed two really valuable guides to my Debian on NSLU2 site that will be of great interest to many NSLU2 users:

• The first guide is for people running Linux on a flash device, such as a USB flash stick. Since flash only supports a limited number of writes, it is important to reduce the wear and tear on the underlying flash device. David's guide gives some practical advice of how to achieve this.
• The second guide gives a few tips and tricks that can be used to reduce the amount of RAM a system uses. This is particularly interesting to NSLU2 users since 32 MB of RAM is not a lot.

These guides mention Debian but most of the advice applies to other NSLU2 firmware flavours and to Linux in general.

NSLU2 tar ball for Debian 4.0r1

I updated the tar ball for the manual Debian/NSLU2 installation to Debian 4.0r1 (including the new 2.6.18-5 kernel) today. The proprietary NPE microcode from Intel is now included in the tar ball since the code no longer has a click-through license.