mypapers/debconf-install/debconf-install.html

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  10
  11     <h1>Automated installations in Skolelinux
  12       <br>using debian-installer and base-config</h1>
  13
  14     <p>Skolelinux is a Debian-based Linux distribution with simple
  15       installation and preconfigured services targeted for schools.
  16       The presentation will present how the standard debian
  17       installation system is customised for this purpose.</p>
  18
  19     <p><tt><a href="http://www.hungry.com/~pere/mypapers/debconf-install/debconf-install.html">http://www.hungry.com/~pere/mypapers/debconf-install/debconf-install.html</a></tt></p>
  20
  21     <div class="presenter">Petter Reinholdtsen
  22       <br>pere@hungry.com
  23       <br>Debconf3, 2003-07-20</div>
  24
  25     <h2>Skolelinux</h2>
  26     <ul>
  27       <li>Based on Debian/Woody (to get security updates)
  28       <li>Simple installation
  29
  30       <li>Translated to several local languages
  31       <li>Includes all the software needed in primary schools
  32
  33       <li>Preconfigured services (syslog, dns, ntp, dhcp, ssh, ldap,
  34           nfs, smb, smtp, imap, ipp, http, web-proxy, ltsp and more)
  35
  36       <li>No license administration
  37       <li>Admin friendly
  38       <li>Scalable
  39     </ul>
  40
  41     <h2>The Skolelinux architecture</h2>
  42
  43     <p><img src="http://developer.skolelinux.no/arkitektur/network-arch_en.jpg">
  44
  45     <h2>The skolelinux install</h2>
  46     <ul>
  47       <li>Simple (two questions and the root password)
  48       <li>Automatic
  49       <li>Using debian-installer (d-i) and base-config (b-c)
  50       <li>Complete (everything work out of the box)
  51       <li>Very little skolelinux-specific code (two udebs and three
  52         config packages).
  53       <li>Rewriting the config of other packages to get the services
  54         preconfigured out of the box (against policy?)
  55
  56     </ul>
  57
  58     <h2>The two stages of the Debian installation</h2>
  59     <h3>First stage (debian-installer)</h3>
  60     <ul>
  61       <li>Booting from cd/floppy/net/whatever
  62       <li>Installing base system
  63       <li>Making HD bootable
  64     </ul>
  65     <h3>Second stage stage (base-config)</h3>
  66     <ul>
  67       <li>Booting from HD
  68       <li>Installing and configuring the non-base system
  69     </ul>
  70
  71     <h2>The first stage (debian-installer)</h2>
  72     <ul>
  73       <li>Modular
  74       <li>Extendible
  75       <li>Using debconf to ask questions
  76       <li>Can be mostly automatic
  77       <li>Very Flexible
  78     </ul>
  79
  80     <h2>debian-installer structure</h2>
  81     <ul>
  82       <li>Selector for installer modules (udebs)
  83       <li>Select language and region
  84       <li>Autodetect hardware
  85       <li>Locate APT source (CD, Net or floppy)
  86       <li>Load the rest of the installer modules
  87       <li>Partition hard-drive
  88       <li>Make filesystems or swap
  89       <li>Mount filesystems
  90       <li>Install base system
  91       <li>Install kernel
  92       <li>Install boot loader
  93       <li>Reboot
  94     </ul>
  95
  96     <h2>debian-installer hooks</h2>
  97     <ul>
  98       <li>Include or exclude d-i modules
  99       <li>Running script at install system boot time
 100       <li>Include or excluding packages going into the HD
 101       <li>Running scripts before reboot from HD
 102       <li>Partitioning
 103     </ul>
 104
 105     <h2>The second stage (base-config)</h2>
 106     <ul>
 107       <li>Executed from init on first boot
 108       <li>Modular (reading /usr/lib/base-config)
 109       <li>Able to adjust the order of the scripts on the fly using
 110         return codes.
 111       <li>Partly using debconf for configuration decisions.
 112     </ul>
 113
 114     <h2>base-config structure</h2>
 115     <ul>
 116       <li>Generate locale if needed
 117       <li>Start terminal emulator (for non-ascii installs) if needed
 118       <li>Load variables based from first stage (/root/dbootstrap_settings)
 119       <li>Turn off screen saver
 120       <li>Show intro screen
 121       <li>Set up console keyboard
 122       <li>Set up time zone
 123       <li>Configure /etc/passwd, root password and local user
 124       <li>Enable ppp?
 125       <li>Configure APT sources
 126       <li>Select packages to install
 127       <li>Fetch packages
 128       <li>Configure exim
 129       <li>Disable ppp?
 130       <li>Show "successful install" screen
 131       <li>Rewrite /etc/inittab to not start base-config on next boot
 132     </ul>
 133
 134     <h2>base-config hooks</h2>
 135       <ul>
 136         <li>Add scripts to /usr/lib/base-config/
 137         <li>Update debconf database
 138       </ul>
 139     </ul>
 140
 141     <h2>Skolelinux specific code</h2>
 142     <h3>First stage</h3>
 143     <ul>
 144        <li>Shorter language list
 145        <li>Set debconf priority limit to high to get automatic install
 146        <li>Ask about profile and do automatic partitioning for this
 147         profile
 148        <li>Reorder d-i module order using dependencies and menu-item value
 149        <li>Install extra packages into the HD
 150        <li>Pass info to second stage using /root/dbootstrap_settings
 151         and /etc/skolelinux/config
 152     </ul>
 153     <h3>Second stage</h3>
 154     <ul>
 155        <li>Set debconf frontend to non-interactive (most of the time)
 156        <li>Preload debconf answers based on profile choice
 157        <li>Automatically install packages for the given profiles
 158        <li>Rewrite/replace config files based on profile and language
 159        <li>Configure XFree86
 160        <li>Restart servers (except kdm)
 161        <li>Check installation
 162        <li>Restart kdm
 163     </ul>
 164
 165     <h2>Some solved problems</h2>
 166     <ul>
 167
 168       <li>Preloading debconf answers need a dummy question template
 169
 170       <li>Packages with insufficient install configuration support
 171         get their config files rewritten using cfengine.
 172
 173       <li>Selecting packages to install using meta-packages.
 174
 175     </ul>
 176
 177     <h2>Conclusion</h2>
 178
 179     <ul>
 180       <li>The current debian-installer is extendible and can do
 181         automated installation, with the hooks needed by Skolelinux.
 182
 183       <li>The current base-config is is flexible enough for
 184         Skolelinux, but could use more hooks to reduce the amount of
 185         Skolelinux specific code.
 186     </ul>
 187
 188     <h2>References</h2>
 189
 190     <ul>
 191
 192       <li><a href="http://www.skolelinux.no/">Skolelinux web site</a>
 193       <li><a href="http://developer.skolelinux.no/">Skolelinux
 194           developers web site</a>
 195       <li><a href="http://developer.skolelinux.no/arkitektur/arkitektur.html.en">The Skolelinux architeture description</a>
 196       <li><a href="http://people.debian.org/~pere/debian-installer/">debian-installer web page</a>
 197       <li><a href="http://people.debian.org/~pere/debian-installer/hooks.html">Available hooks in debian-installer</a>
 198     </ul>
 199
 200     <h2>Thank you very much</h2>
 201
 202     <h3>Questions?</h3>
 203
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