Knoppix, or KNOPPIX is a Linux distribution based on Debian designed to be run directly from a CD / DVD. Knoppix was developed by Linux consultant Klaus Knopper. When starting a program it is loaded from the optical disc and decompressed into a RAM drive. The decompression is transparent and on-the-fly.

 Although Knoppix is primarily designed to be used as a Live CD, it can also be installed on a hard disk like a typical operating system. Computers that support booting from USB devices can load Knoppix from a live USB flash drive or memory card. There are two main editions of Knoppix: the traditional Compact Disc (700 megabytes) edition and the DVD (4.7 gigabytes) "Maxi" edition. Each of these main editions has two language-specific editions: English and German. Knoppix mostly consists of free software, but also includes proprietary software.

 Usage

 Knoppix can be used to back up files easily from hard drives with inaccessible operating systems. To quickly and more safely use Linux software the Live CD can be used instead of installing another OS.

 Contents

 More than 1000 software packages are included on the CD edition and more than 2600 are included on the DVD edition. Up to 9 gigabytes can be stored on the DVD in compressed form. These packages include:

• Part of KDE, the default desktop environment, including the Konqueror web browser and the KMail e-mail client. Knoppix is also packaged with several other window managers, including, Fluxbox, twm, IceWM, and GNUstep.
• XMMS, with MP3 audio, and Ogg Vorbis audio playback support
• Internet access software, including the KPPP dialer and ISDN utilities
• The Iceweasel web browser (based on Mozilla Firefox)
• K3b, for CD (and DVD) authoring and backup
• GIMP, an image manipulation program
• Tools for data rescue and system repair
• Network analysis and administration tools
• OpenOffice.org, a comprehensive office suite
• Many programming and development tools
  

Requirements

Requirements to run Knoppix:

• Intel-compatible processor (i486 or later)
• 32 MB of RAM for text mode, at least 96 MB for graphics mode with KDE (at least 128 MB of RAM is recommended to use the various office products)
• Bootable CD-ROM drive, or a boot floppy and standard CD-ROM (IDE/ATAPI or SCSI)
• Standard SVGA-compatible graphics card
• Serial or PS/2 standard mouse or IMPS/2-compatible USB-mouse
  

Saving changes in the environment

Prior to Knoppix 3.8.2, any documents or settings a user created would disappear upon reboot. This lack of permanence made it necessary to save documents explicitly to a hard drive partition, over the network, or to some removable medium, such as a USB flash drive.

It was also possible to set up a "persistent home directory", where any documents or settings written to the user's home directory would automatically be redirected to a hard drive or removable medium, which could be automatically mounted on bootup. What is stored there physically is a file called knoppix.img. The file is used to simulate a file system into which files are written for later use. This is transparent for the user. What the user perceives is that it is possible to write files to the home directory.

Union mount support was added in version 3.8.1 through UnionFS. This was later replaced in 5.1.0 by Aufs to improve stability. The union mount allows virtual updates to the data on the read-only CD/DVD medium by storing changes on a separate writable medium and then representing the combination of the two as single storage device. The writable medium can be memory (ramdisk), a hard disk, USB flash drive, etc. This means that the user can modify the software installed on the Knoppix system, such as by using APT to install or update software. The storage device containing the changes needs to be present whenever Knoppix is started else only the original data from the disc will be used.

By default Knoppix will scan available storage devices for a persistent home directory, but you can override this scan and provide a specific location with a boot option (see below) such as: home=/dev/hda1/knoppix.img

By carrying a Knoppix CD and a USB flash drive, a user can have the same environment, programs, settings, and data available on any computer that is Knoppix-compatible.

Boot options

When using Knoppix as a Live CD, one can use boot options, also known as 'cheatcodes', to override a default setting or automatic hardware detection when it fails. For example, the user may wish to boot into a plain console, or proceed without SCSI support. For this, Knoppix allows the user to enter one or more cheat codes at the prompt before booting. If the user doesn't enter a cheat code, or doesn't press any key before the timeout, Knoppix will boot with its default options. For example, to set the language to French rather than the default, one would type:

knoppix lang=fr

Popularity

Knoppix was one of the first Live CD Linux distributions to gain popularity.[4] There are several factors that contribute to the popularity of Knoppix:

• Knoppix was one of the first Live CDs available, and is known as the "original" Debian-based Live CD
• Its extensive hardware detection allows most systems to start Knoppix without any configuration
• Its ability to automatically connect to most kinds of networks
• Its utilities for system repair and troubleshooting
  

Knoppix works on a fairly high number of PCs or laptops, but not all. The automatic hardware detection cannot cope with all hardware, and sometimes the drivers used will not be optimal. Knoppix has difficulty recognizing some cards made before 1998, or motherboards with BIOS made before 2002. (In some cases, manual configuration with codes entered at boot time can overcome problems with automatic detection.

If a PC does not have enough RAM to run KDE and other included programs, Knoppix boots up a very limited twm session instead. The only window running in the twm session by default is xterm.