Package: debian-installer-manual Severity: normal
This is a first attempt at documenting the auto mode and auto-install It also updates the stuff about network preseeding to reflect the fact that you can chain into network preseeding by setting preseed/url in an earlier preseed, as long as you're not trying a stand-alone networkless install, obviously. Related to this, we should probably have a section that includes the preseed_aliases file amd documents it, so that we can add references to that section where needed. Cheers, Phil. Index: en/appendix/preseed.xml =================================================================== --- en/appendix/preseed.xml (revision 42292) +++ en/appendix/preseed.xml (working copy) @@ -48,9 +48,7 @@ <firstterm>network</firstterm>. Initrd preseeding will work with any installation method and supports preseeding of more things, but it requires the most preparation. File and network preseeding each can be used with -different installation methods. With file and network preseeding the first -few installer questions cannot be preseeded because the preconfiguration -file is only loaded after they have been asked. +different installation methods. </para><para> @@ -71,7 +69,8 @@ <entry>CD/DVD</entry> <entry>yes</entry> <entry>yes</entry> - <entry>no</entry> + <entry>yes<footnote id='apx-ps-net'><para> + but only if you have network access, and set preseed/url appropriately</para></footnote></entry> </row><row> <entry>netboot</entry> <entry>yes</entry> @@ -81,12 +80,12 @@ <entry>hd-media <phrase condition="bootable-usb">(including usb-stick)</phrase></entry> <entry>yes</entry> <entry>yes</entry> - <entry>no</entry> + <entry>yes<footnoteref linkend='apx-ps-net'/></entry> </row><row condition="supports-floppy-boot"> <entry>floppy based (cd-drivers)</entry> <entry>yes</entry> <entry>yes</entry> - <entry>no</entry> + <entry>yes<footnoteref linkend='apx-ps-net'/></entry> </row><row condition="supports-floppy-boot"> <entry>floppy based (net-drivers)</entry> <entry>yes</entry> @@ -113,19 +112,28 @@ </para><para> -In practical terms this means for file and network preseeding that the -questions about language, country and keyboard selection will already have -been asked. For network preseeding add to that any questions related to -network configuration. Some other questions that are only displayed -at medium or low priority (like the first hardware detection run) will -also already have been processed. +In order to facilitate preseeding of the questions that would normally +appear before the file or network preseeding occur, one can start the +installer in <quote>auto</quote> mode by entering +<userinput>auto</userinput> and parameters to indicate the source of +the preseed file, as required, at the boot prompt. This sets +auto-install/enabled=true for you, which results in questions that +would normally be asked too early for preseeding (i.e. language, +country and keyboard selection) to be delayed until after the network +comes up, thus allowing them to be preseeded then. Of course, if you +need to set the up network with static IP address, that will still +need to be done either by hand, or by specifying these settings via +one of the methods that are available before the network is used (at +the boot prompt, or via initrd, file preseeding or perhaps via DHCP). +<quote>auto</quote> mode also sets debconf/priority=critical for you. </para><para> Obviously, any questions that have been processed before the -preconfiguration file is loaded cannot be preseeded. -<xref linkend="preseed-bootparms"/> offers a way to avoid these -questions being asked. +preconfiguration file is loaded cannot be preseeded (this will include +questions that are only displayed at medium or low priority, like the +first hardware detection run). <xref linkend="preseed-bootparms"/> +offers a way to avoid these questions being asked. </para> </sect2> @@ -324,8 +332,9 @@ </para><para> -While you're at it, you may want to add a boot parameter -<userinput>priority=critical</userinput>. This will avoid most +While you're at it, you may want to take advantage of <xref +linkend="preseed-auto"/>, which adds a boot parameter +<userinput>priority=critical</userinput> for you. This will avoid most questions even if the preseeding below misses some. </para> @@ -368,6 +377,108 @@ </para> </sect2> + <sect2 id="preseed-auto"> + <title>Auto mode</title> +<para> + +There are several features of Debian-installer that combine to allow +fairly simple command lines at the boot prompt to result in +arbitrarily complex customised automatic installs. To illustrate +this, here are some examples that can be used at the boot prompt: + +<informalexample><screen> + auto url=autoserver +</screen></informalexample> + +This relies on there being a DHCP server that will get the machine to +the point where <literal>autoserver</literal> can be resolved by DNS, +perhaps after adding the local domain if that was provided by DHCP. +If this was done at a site where the domain is +<literal>example.com</literal>, and they have a reasonably sane DHCP +setup, it would result in the preseed file being retrieved from +<literal>http://autoserver.example.com/d-i/etch/./preseed.cfg</literal>. +The the path segment of that comes from +<literal>auto-install/defaultroot</literal>, which includes the +directory <literal>etch</literal> by default to allow future versions +to specify their own codename to let people migrate forwards in a +controlled manner. The <literal>/./</literal> bit is used to indicate +a root relative to which subsequent paths can be anchored (for use in +preseed/include and presseed/run). This allows files to be specified +either as full URLs, paths starting with / that are thus anchored, or +even paths relative to the location where the last freseed file was +found. This can be used to construct more portable scripts where an +entire hierarchy of scripts can be moved to a new location without +breaking it, for example copying the files onto a USB stick when they +started out on a web server. In this example, if the preseed file +sets <literal>preseed/run</literal> to +<literal>/scripts/late_command.sh</literal> then the file will be +fetched from +<literal>http://autoserver.example.com/d-i/etch/./scripts/late_command.sh</literal>. + +</para><para> + +Of course, if there is no local DHCP or DNS infrastructure, or if you +do not want to use the default path to the preseed.cfg, one can still +use an explicit url, and if you don't use the <literal>/./</literal> +element it will be anchored to the start of the path (i.e. the third / +in the URL). Here is an example that requires minimal support from +the local network infrastructure: + +<informalexample><screen> + auto url=http://192.168.1.2/path/to/mypreseed.file +</screen></informalexample> + +The way this works is that if the URL is missing a protocol, http is +assumed, if the hostname section had no full-stops, it has the domain +derived from DHCP appended to it, and if there's no /'s after the +hostname, then the default path is added. + +</para><para> + +In addition to specifying the url, one can also specify settings that +do not directly affect the behavior of debian-installer itself, but +can be passed through to any scripts that might be specified +preseed/run settings in the loaded preseed file. At present, the only +example of this is <literal>auto-install/classes</literal>, which has +an alias <literal>classes</literal>. This can be used thus: + +<informalexample><screen> + auto url=hands.com classes=xen3 +</screen></informalexample> + +refer to http://hands.com/d-i/ for more details how this example +works. If you want to come up with other paradigms, it is reasonable +to use the auto-install namespace for this, so one might have +something like <literal>auto-install/style</literal> which is then +used in your scripts. If you feel the need to do this, please mention +it to the debian-boot mailing list so that we can avoid namespace +conflicts, and perhaps add a preseed_alias for you. + +</para><para> + +The <literal>auto</literal> boot label is not yet definied on all +architectures. The same effect may be achieved by simply adding the +two settings <literal>auto=true priority=critical</literal> to the +kernel command line yourself to achieve the same effect. The +<literal>auto</literal> is an alias for +<literal>auto-install/enabled</literal> and controls the delay of the +locale and keyboard questions until after there has been a chance to +preseed them, while <literal>priority</literal> is an alias for +<literal>preseed/priority</literal> and setting it to +<literal>critical</literal> stops any questions with a lower priority +from being asked. + +</para><para> + +Additional options that may be of interest while attempting to +automate an install while using DHCP are: <literal>interface=auto +netcfg/dhcp_timeout=60</literal> which makes the machine choose the +first viable NIC and be more patient about getting a reply to it's +DHCP query. + +</para> + </sect2> + <sect2 id="preseed-bootparms"> <title>Using boot parameters to supplement preseeding</title> <para> @@ -388,9 +499,12 @@ </para><para> -Note that some variables that are frequently set at the boot prompt have a -shorter alias. If an alias is available, it is used in the examples in -this appendix instead of the full variable. +Note that some variables that are frequently set at the boot prompt +have a shorter alias. If an alias is available, it is used in the +examples in this appendix instead of the full variable. In +particular, the <literal>preseed/url</literal> variable has been +aliased as <literal>url</literal> and has some extra magic to allow +shortened urls to be used. </para><para> @@ -1226,7 +1340,7 @@ </para> <informalexample><screen> -# More that one file can be listed, separated by spaces; all will be +# More than one file can be listed, separated by spaces; all will be # loaded. The included files can have preseed/include directives of their # own as well. Note that if the filenames are relative, they are taken from # the same directory as the preconfiguration file that includes them. @@ -1249,6 +1363,19 @@ d-i preseed/run string foo.sh </screen></informalexample> +<para> + +It is also possible to chainload from the initrd or file preseeding +phase, into networking preseeding by setting preseed/url in the earlier +files. This will cause network preseeding to be performed when the +network comes up. One needs to be careful in one's assumptions when +doing this, since there will be two distinct runs at preseeding, +meaning for example that one gets another chance to run the +preseed/early command, the second one happening after the network +comes up. + +</para> + </sect2> </sect1> </appendix> -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
