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