UML Home Page: user-mode-linux.sourceforge.net
UML Wiki: uml.harlowhill.com/index.php/Chroot
Rusty Russell's Comprehensive User-Mode Linux HOWTO: user-mode-linux.sourceforge.net/UserModeLinux-HOWTO.html
Nagafix Ltd.'s download site, where you can obtain root filesystem images, maintained with current security patches, for a variety of Linux distributions: uml.nagafix.co.uk
David Cannings' excellent article “Networking UML Using Bridging”: edeca.net/articles/bridging
Michael McCabe and Demetrios Dimatos' article “Installing User Mode Linux”, which includes a root filesystem-creation procedure: www.clarkson.edu/class/cs644/kernel/setup/uml/uml.html
Tom Fawcett's Linux Bootdisk HOWTO. Of particular relevance here is Section 4, “Building a Root Filesystem”: www.tldp.org/HOWTO/Bootdisk-HOWTO