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diff --git a/build_tools/clarch/larch/docs/html/larch_live_system.html b/build_tools/clarch/larch/docs/html/larch_live_system.html deleted file mode 100644 index 5cd6f40..0000000 --- a/build_tools/clarch/larch/docs/html/larch_live_system.html +++ /dev/null @@ -1,155 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> -<html> -<head> - <meta content="text/html;charset=UTF-8" http-equiv="Content-Type"> - <title>larch live system structure</title> - <meta content="gradgrind" name="author"> -</head> - -<body> - -<table style="text-align: left; width: 100%;" border="1" cellpadding="2" cellspacing="2"> - <tbody> - <tr> - <td><a href="larch_profiles.html">Previous: Profiles</a></td> - - <td><a href="larch_docindex.html">Table of Contents</a></td> - - <td><a href="larch_fstab.html">Next: /etc/fstab</a></td> - </tr> - </tbody> -</table> - -<br /> - -<h1><big>larch</big> -– -a do-it-yourself live <em>Arch Linux</em> CD</h1> - -<img style="border: 0px solid ; width: 320px; height: 320px;" alt="" src="larch1.jpg" - name="graphics1" align="right" hspace="10" vspace="10" /> -<br /><br /> - -<h2>Structure of a <em>larch</em> live CD</h2> - -<p>The vast majority of the code that runs in a live CD/USB system is exactly -the same as in a normal system running from hard disk. -The main differences arise through the live CD/USB system being based on -a read-only root file-system, so various adjustments are necessary to -make the areas that must be writable appear to be so. I say 'appear to be' -because in general any changes will be lost when the system shuts down, -the actual changes being made only in a RAM-based filesystem (but see -<a href="larch_sessionsave.html">"Session saving"</a>). -</p> - -<h3><a name="Squashfs_and_Unionfs"></a>squashfs and aufs</h3> - -<p>In <em>larch</em>, as in many other live CD/USB systems, the ability to (apparently) -write to a read-only file-system is provided by <em>aufs</em> (originally -derived from <em>unionfs</em>). -The file-system is also compressed, using <em>squashfs</em>, so as to fit more data -onto the storage device (normally about 2GB of uncompressed code and data -can be squeezed onto a 700MB CDROM using this approach). A custom -<em>Arch Linux</em> installation (you can choose which packages are installed) is -compressed into a <em>squashfs</em> file-system in the file -<strong>system.sqf</strong>, which is placed in the root directory of the boot device. -</p> - -<p>For use in a live CD/USB system a few changes must be made to some files in the -installation. In <em>larch</em> this is (at first) not done directly, the installed -system is left in a 'clean' state. Instead of that, an additional <em>union</em> layer -is created, in the archive <strong>mods.sqf</strong>, -containing all the modified files (except those in /etc, which are placed in the -top, writable, <em>union</em> layer, which is saved in the <strong>overlay.ovl</strong> archive. -The user is free to include (pretty well) any customizations (s)he wants in these -overlay files. These files are also placed in the root directory of the boot device. -</p> - -<p>These system archives are combined when the live CD/USB system -boots. They are mounted as branches of a <em>union</em> file-system with -the overlay above the 'standard' system, so that files in the overlay have -priority over the original ones. The top layer of the <em>union</em> is a <em>tmpfs</em> -writable layer (thus, effectively, making the whole system writable), -into which the archive <strong>overlay.ovl</strong> is unpacked during booting. -As the changes are only stored in RAM, they will, however, be lost when the system shuts -down (unless using the <a href="larch_sessionsave.html">session saving</a> feature). -</p> - -<h3><a name="initramfs"></a><em>initramfs</em> and <em>mkinitcpio</em></h3> - -<p>It is, in general, not possible to boot directly into a live CD/USB system. -Some form of 'initrd' or 'initramfs' is required, in order to find the boot -device, get hold of the file-system and prepare it for running. -Many modern <em>GNU/Linux</em> systems use initrd/initramfs (the former being now deprecated) -as a matter of course, for loading the necessary kernel modules, and -<em>Arch Linux</em> is no exception, a modular initramfs system (<em>mkinitcpio</em>) -being the standard way to boot <em>Arch Linux</em>, and <em>larch</em> also takes -advantage of it, although some additions need to be made to boot live CD/USB systems. -</p> - -<h3><a name="rc_files"></a>/etc/inittab, /etc/rc.sysinit and /etc/rc.shutdown</h3> - -<p>The initial boot script and the shutdown script must be customized for use -in a larch live environment. There are numerous ways of achieving that and -<em>larch</em> has tried out several. In version 5.3.2 a method was introduced which -involves replacing the original /etc/rc.sysinit and /etc/rc.shutdown scripts -by modified versions which are fully equivalent to the official scripts but -split off certain parts into functions which can be overridden when used in a -<em>larch</em> live system. The 'larch-live' package provides the files -/etc/larch-sysinit and /etc/larch-shutdown which provide the new versions -of these functions for live use. -<p>The need to overwrite certain system files is a bit messy, and means that -the initscripts package should not be updated in the live system, but I -hope the official package will sometime itself contain suitable versions of the -'/etc/rc.sysinit' and '/etc/rc.shutdown' files which separate out the -relevant functions so that larch doesn't need to overwrite them. -</p> -<p>Although it is not strictly necessary (because the substituted files are -fully equivalent to the official ones), larch saves the originals as -'/etc/rc.sysinit.larchsave' and '/etc/rc.shutdown.larchsave', so that these -can be restored on installation by <em>larchin</em> (this might avoid later -confusion). -</p> - -<p>It is possible to use a customized version of '/etc/inittab', by -putting the new version in the <em>profile</em> (in 'rootoverlay') - for -example one could customize the handling of the first terminal, e.g. to -allow automatic login. -The original <em>inittab</em> is saved as '/etc/inittab.larchsave', -so that it can be restored if the system is installed using <em>larchin</em>. -</p> - -<p>One addition in the <em>larch</em> version of the initscripts is the -automatic generation of a new '/etc/fstab' (using the script -<strong>gen_fstab</strong>, which -bases the result on the devices which are detected in the system). Otherwise -it behaves much the same as the version in -a normal <em>Arch Linux</em> system. However, the remount of the root-filessystem and -file-system checks have been left out as they are not relevant in a live-CD -environment. No partitions are mounted and, by default, swap is not enabled. -The reason is primarily that for use as an installation CD, it is better not -to have any partitions mounted, because it is quite likely that the partitions -will be edited in preparation for the installation. Passing boot parameter -'swap' will enable swap if there is a suitable partition (or it can be done -manually using 'swapon -a'). -</p> - -<p>'/etc/rc.shutdown' is adapted by -adding code to deal with session-saving (writing changes back to the boot medium) -and to eject the live-CD. Unlike in the normal version, the hardware clock is not reset. -</p> - -<table style="text-align: left; width: 100%;" border="1" cellpadding="2" cellspacing="2"> - <tbody> - <tr> - <td><a href="larch_profiles.html">Previous: Profiles</a></td> - - <td><a href="larch_docindex.html">Table of Contents</a></td> - - <td><a href="larch_fstab.html">Next: /etc/fstab</a></td> - </tr> - </tbody> -</table> - -</body> -</html> |