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larch is a collection of scripts designed around the creation and use of live CD/DVD/USB-stick versions of Arch Linux.
One design aim was easy customization, so that even relatively inexperienced users could build personalized live CDs (etc.), containing whatever packages they wanted and with their own personal configurations. The resulting medium should also be usable for installation purposes, so that one has a customized Arch Linux installation/rescue medium. As the content can be chosen freely, a comfortable working environment is possible - in contrast to the rather Spartan standard Arch installation CD.
larch also offers a flexible approach to building your live media. You can use 'profiles' to determine what gets installed, and how it is configured. The advantage of this method is that all your specifications are kept together in a folder which can be used to rebuild the same or a similar system at a later date. Alternatively you can do a normal Arch Linux installation (if there is such a thing!) and then make a live medium from this. You can even 'livify' your existing installation (though it might be worth tidying it up a bit first ...).
Squashfs offers convenient compression of the data on the CD so that up to about 2 GB of code can be included on a 700 MB CD. aufs (a 'unification' file system, originally based on unionfs) offers the ability to write to all directories even though the CDROM is read-only, which allows such fancy stuff as installation of new software packages to the running live system. Using aufs you could do, say, 'pacman -S fluxbox' and fluxbox would be installed. The limit to the amount of overwriting is determined by the size of the available memory.
All this would normally be gone when you reboot as the changes are really only stored in memory. However, thanks to various technical wizardry, it is also possible (on suitable media) to save any changes you make while running the live system back to the medium on shutdown.
Hardware detection is provided by the same udev approach as is used in a standard Arch Linux system.
The larch project comprises several components. The scripts for building a larch live medium are in the larch package, which need not itself be installed in the live system, though it may be useful. Scripts and data for the live environment are provided in the larch-live package, which must be installed in the live system. There is also an optional installer (larchin, written in python and bash, with a GTK interface) which can install the live system to hard disk, providing a convenient way to install a ready-configured Arch Linux system.
I have tried to maintain the distribution-independence of the larch scripts, so that they can be used on other GNU/Linux systems - you shouldn't need an Arch Linux installation in order to build a larch live medium, the dependencies (e.g. bash, wget, mkisofs ) should be satisfied on pretty well any GNU/Linux system (and a static version of pacman can be downloaded). In other words, it should not be difficult to generate your own customized larch CD on pretty well any GNU/Linux system. But I must admit that this feature hasn't been tested much.
As with most stuff around Arch Linux it's not really designed for beginners - you should know your way around a GNU/Linux system (preferably Arch!), and have at least a minimal idea of running command-line stuff and editing configuration files. In any case, I hope that the documentation will be clear enough to help anyone who wants to exploit larch to the full (feedback is welcome!).
Requirement: You need quite a lot of space to create an Arch Linux live CD system - to build a 700MB CD image you'll need up to about 4GB. That is because a complete Arch Linux system is installed, then a compressed ('squashed') verion is made, and then a CD image (iso). Building for a USB-stick requires slightly less space, as the iso-image is not built.
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