Klaus Knopper answers your Linux questions
Ask Klaus
Klaus Knopper is the creator of Knoppix and co-founder of LinuxTag expo. He currently works as a teacher, programmer, and consultant. If you have a configuration problem, or if you just want to learn more about how Linux works, send your questions to: klaus@linux-magazine.com
Overlay Partitions
Klaus: Knoppix 7.0.5 has a new experimental feature, allowing an overlay on a separate partition of a USB flash disk. Can you explain how it works?
Most Live distros use a (ram)disk overlay nowadays to allow virtual write access to files on a read-only medium. Before overlay filesystems like UnionFS and Aufs came into existence, you had to copy all directories that needed to be writable for configuration and storage of intermediate data (e.g., subdirectories of /var, /home, and /etc) to the ramdisk, and create symlinks on the ramdisk back to the read-only parts located on CD or DVD to keep RAM usage down.