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diff --git a/build_tools/larch7/larch0/docs/html/larch_live_system.html b/build_tools/larch7/larch0/docs/html/larch_live_system.html deleted file mode 100644 index 1f7bbeb..0000000 --- a/build_tools/larch7/larch0/docs/html/larch_live_system.html +++ /dev/null @@ -1,220 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/xhtml1-strict.dtd"> -<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> - -<html> -<head> -<meta http-equiv="Content-type" content="text/html; charset=utf-8" /> -<title>Structure of a larch live system</title> -<!-- (en) Add your meta data here --> - -<link href="css/larchdocs.css" rel="stylesheet" type="text/css"/> -<!--[if lte IE 7]> -<link href="css/yaml/core/iehacks.css" rel="stylesheet" type="text/css" /> -<![endif]--> -</head> - -<body> -<!-- skip link navigation --> -<ul id="skiplinks"> - <li><a class="skip" href="#col1">Skip to main content (Press Enter).</a></li> -</ul> - -<div class="page_margins"> - <div class="page"> - <div id="top"><div id="tm"></div></div> - <!-- begin: #col1 --> - <div id="col1" role="main"> - <div id="col1_content"> - <div id="header" role="banner"> - <h1><span><em>live Arch Linux</em> builder</span></h1> - </div> - - <!-- begin: #col3 navigation column --> - <div id="col3" role="complementary"> - <div id="col3_content"> - <img class="indent2" alt="larch logo" src="css/screen/larch150x.png" width="150" height="150" /> - <div class="vlist"> - <ul> - <li><a href="index.html"><h6>Table Of Contents</h6></a></li> - <li><a href="larch_sessionsave.html"><h6>Next:</h6> - <div class="indent1">Saving a session back to the boot device (or even somewhere else)</div></a></li> - <li><a href="profiles.html"><h6>Previous:</h6> - <div class="indent1">Profiles</div></a></li> - </ul> - </div> - </div> - </div> - <!-- end: #col3 --> - -<div class="larchdocs"> -<h2 id="pagetitle" level="1">Structure of a <em>larch live</em> system</h2> - -<p>The vast majority of the code that runs in a <em>live</em> CD/USB system -is exactly the same as in a normal system running from hard disk. -The main differences arise through the <em>live</em> system being based on -a read-only root file-system, so various adjustments are necessary to -make the areas that must be writeable 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 <em>live</em> 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. 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 'larch' directory of the boot device. -</p> - -<p>For use in a <em>live</em> system a few changes must be made to some files -in the installation. In <em>larch</em> this is usually 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. The user is free to include (pretty well) -any customizations (s)he wants in this overlay file, which is also placed -in the 'larch' directory of the boot device. -</p> - -<p>Using <em>larch</em>'s merge-overlay feature it is possible to -rebuild the 'mods.sqf' archive to incorporate subsequent changes to the -system. When this is done an additional <em>union</em> layer -(<strong>filter.sqf</strong>) will be created. For further details see the -<a href="larch_sessionsave.html">session saving page</a>. -</p> - -<p>These system archives are combined when the <em>live</em> system -boots. They are mounted as branches of a <em>union</em> (<em>aufs</em>) -file-system with the overlay above the 'standard' system, so that files in -the overlay have priority over the original ones. A further, <em>tmpfs</em>, -layer is placed on top of these, which effectively makes the whole system -writeable. When <a href="larch_sessionsave.html">session saving</a> is being -used this top layer is initialized during the boot sequence, by copying the -contents of a compressed archive (<strong>overlay.tar.lzo</strong>) into it. -<em>lzo</em> compression is used here because of its speed ('lzop' is a -dependency of the 'larch-live' package). -</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 <em>live</em> -system. -Some form of 'initrd' or 'initramfs' is required, in order to find the boot -device, prepare the <em>union</em> 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 <em>live</em> systems. -</p> - -<p><em>larch</em> adds several 'hooks' (code plug-ins) to the -<em>Arch Linux mkinitcpio</em> system (they are in the 'larch-live' package). -The first, 'larch1', is concerned with finding the boot device. -It can select a device on the basis -of UUID, partition label, partition name ('/dev/sdb1', etc.) or else it can -search all available devices for the file '/larch/larchboot'. A simple -validity check is made by testing the existence of the '/larch/system.sqf' -archive. -</p> - -<p>The second hook comes in two flavours - one for <em>aufs</em> and one -for <em>unionfs</em> - it just sets some variables according to which -unioning file-system is being used (at the moment only <em>aufs</em> -is properly supported). -</p> - -<p>The third hook, 'larch3', performs the actual preparation of the -<em>larch</em> root file-system, combining the system and overlay archives -with a <em>tmpfs</em> upper layer in a <em>union</em> and carrying out -various other initializations. -</p> - -<p>In order to generate the special <em>initramfs</em> a customized -'/etc/mkinitcpio.conf' is used, prepared during the build process from the -template '/etc/mkinitcpio.conf.larch0' and saved as -'/etc/mkinitcpio.conf.larch'. If you want to customize this, you need to -edit '/etc/mkinitcpio.conf.larch0' in 'rootoverlay' in the profile (the -gui has a button for this). -</p> - -<p>There is also a customized <em>mkinitcpio</em> preset in '/etc/mkinitcpio.d', -also working with a template - 'larch.preset0' is used to produce 'larch.preset' -during the build operation. In addition this preset replaces the standard -preset belonging to the kernel, so that subsequent kernel updates (etc.) -will regenerate a correct <em>initramfs</em> for the <em>larch</em> system. -If you want to revert to the normal <em>Arch Linux mkinitcpio</em> behaviour -(for example, if you are installing the system) you will need to replace -the preset by the original, which gets saved with '.larchsave' appended. -</p> - - -<h3><a name="rc_files"></a>/etc/rc.sysinit and /etc/rc.shutdown</h3> - -<p>The initial boot script and the shutdown script must be customized for use -in a <em>larch live</em> environment. This is achieved by using hooks in the -standard /etc/rc.sysinit and /etc/rc.shutdown scripts. The file -'etc/rc.d/functions.d/larch-hooks', in the 'larch-live' package, defines these. -During startup the main tweaks are to the content of /etc/mtab and /etc/fstab. -During shutdown we probably want to disable writing to the hardware clock, but -the main addition is the session saving code. If booting from CD/DVD we will -want to eject this just before shutting down. -</p> - -<h3><a name="fstab"></a>/etc/fstab</h3> - -<p>If the file '/etc/fstab.larch' exists this will be used as a persistent -'/etc/fstab', being copied there during the boot process (in the 'larch3' -hook in the initramfs system). Otherwise a very minimal '/etc/fstab' will -be generated at each boot. It includes entries for any existing swap -partitions, but these are commented out unless the 'swap' boot parameter -is specified (the default <em>larch</em> behaviour is to mount nothing -automatically). -</p> - -<p>The 'x10d_fstab' script in the 'larch-live' package allows the very basic -/etc/fstab generated by the initramfs system ('larch3' hook) to be extended -automatically, but '/etc/fstab' will only be changed if '/etc/fstab.larch' -doesn't exist. -This script adds entries for the partitions it detects, and also mount points -in '/mnt' for them. The entries are such that the partitions are not mounted -automatically. -</p> - -<h3><a name="aufs"></a>[<em>unionfs as an alternative to aufs</em>]</h3> - -<p>In principle, <em>unionfs</em> can be used instead of <em>aufs</em>, -but as <em>aufs</em> is supported by current <em>Arch Linux</em> kernels -it is obviously the first choice. Indeed the current <em>larch</em> code -probably won't work with <em>unionfs</em>, as it hasn't been tested - but -the framework to support it is in place. -</p> - - -</div> - - - <div class="topref"><a href="#top">Top</a></div> - </div> - <!-- begin: #footer --> - <div id="footer"> - <div id="footer-content" role="contentinfo">© 2010 Michael Towers<br /> - Page layout assisted by <a href="http://www.yaml.de/">YAML</a> and - <a href="http://www.kuwata-lab.com/tenjin/">pyTenjin</a> - </div> - </div> - <!-- end: #footer --> - </div> - <!-- end: #col1 --> - <div id="bottom"><div id="bl"><div id="bm"></div></div></div> - </div> -</div> -<!-- full skiplink functionality in webkit browsers --> -<script src="css/yaml/core/js/webkit-focusfix.js" type="text/javascript"></script> -</body> -</html> |