The instructions for installing an NSLU2 are designed for using a Windows box - but it’s easy enough to set it up using any OS. Just use the web server built in, and use an address of 192.168.1.77 and username/password of admin/admin.
Following the NSLU2-Linux instructions on unslinging is easy too, except I didn’t know what to do after unslinging and rebooting - ie I cannot telnet back into the box! What you need to do is change the password after connecting the disk but before rebooting:
# passwd
[enter new password twice]
# cp /etc/passwd /share/hdd/conf/passwd
# ln -sf /share/hdd/conf/passwd /etc/passwd
Then you need to reboot (or maybe you don’t, I did just to test the password stuck!), re-enable telnet login, and you can begin to install packages.