Editing Live CD (section)

== Creation ==


A read-only [[file system]], such as on a CD-ROM has the drawback of being unable to save any current working data. For this reason, a read-only file system is often merged with a temporary writable file system in the form of a [[RAM disk]]. Often the default Linux [[file directory|directories]] "<code>/home</code>" (containing users' personal files and [[configuration file]]s) and "<code>/var</code>" (containing variable [[data (computing)|data]]) are kept in ramdisk, because the system updates them frequently. Puppy Linux and some other live CDs allow a configuration and added files to be written and used in later sessions.

In modern live CDs, a read-only file system is merged with a [[RAM drive]] using [[transparency (human-computer interaction)|transparent]] techniques such as [[UnionFS]], [[AuFS]] or [[Enhanced Write Filter|EWF]]. Boot loaders like syslinux can boot ISO files from USB memory devices.

Live CDs have to be able to detect and use a wide variety of hardware (including [[network card]]s, [[graphic card]]s etc.) in realtime, often using facilities such as [[udev]], [[hotplug (software)|hotplug]], hal, udisk etc.. which are a common part of all distributions based on [[Linux kernel]] 2.6.