There are detailed installation instructions made by Martin Michlmayr.
Here are my short notes:
1. Install firmware upload tool upslug2 to host system. Upslug2 is available in Ubuntu repositories.
# sudo apt-get install upslug2
2. Download and extract latest stable installer image (unofficial version with proprietary code). At the moment of writing this, the 6.0 Beta2 release does not appear to install properly. Device reboots when performing hardware detection. Latest stable 5.0.4 works fine.
http://www.slug-firmware.net/d-dls.php
3. Boot NSLU2 to upgrade mode by pressing reset button for 10 sec while switching power on. Have all disks disconnected.
4. Upload firmware to NSLU2
# sudo upslug2 -i di-nslu2.bin
5. After installer installation is finnish, log in to the installer with password install. The IP address depens on your DHCP settings.
# ssh installer@192.168.1.101
6. Insert flash disk (USB Memory stick or SD card) and start installer.
7. In disk partition phase, select manual partition. Allocate both ext2 and swap partitions. Select noatime option and set mount point /
8. Once installation is ready, configure your setting and do some optimization for flash and low memory use.
Network settings /etc/network/interfaces
iface eth0 inet static address 192.168.1.20 network 192.168.1.0 netmask 255.255.255.0 gateway 192.168.1.1