Emdebian Multistrap information
[ Multistrap overview ] [ Secure Apt ] [ Example configurations ] [ Using multistrap for pbuilder chroots ] [ Multiple repositories ] [ Cascading configuration ] [ Cross building support ] [ Multistrap Wiki page ]
Cascading configuration means sharing common configuration settings between similar variants of bootstraps. This allows multiple variants, all using the same basic settings - no point writing the same script multiple times to do the same thing for different setups. A configuration file for multistrap could be defined as base and another as variant. The variant declares an includes field which specifies the base file to use for the rest of the settings.
Variant would include only those settings from [General] that differ between variants and then a number of sections, like Grip, GripUpdate, Debian, Local etc.
Base would include the core settings that don't change and maybe one section for the base packages.
The current configuration files for pdebuild-cross use cascading multistrap configurations to organise the various cross-building toolchains with more general purpose package building support.
Variant configuration file
[General] include=/usr/share/multistrap/crosschroot.conf omitrequired=false configscript= setupscript=/usr/share/multistrap/setcrossarch.sh debootstrap=Debian Base Toolchains aptsources=Debian Toolchains tarballname=pdebuild-cross.tgz [Toolchains] packages=g++-4.2-arm-linux-gnueabi linux-libc-dev-armel-cross reinstall=binutils-multiarch source=http://www.emdebian.org/debian keyring=emdebian-archive-keyring suite=stable
General cross-building chroot configuration
[General] arch= directory= cleanup=true noauth=false unpack=true debootstrap=Debian Base aptsources=Debian [Base] packages=gcc-4.2-base source=http://ftp.uk.debian.org/debian keyring=debian-archive-keyring suite=stable [Debian] packages=dpkg-dev binutils-multiarch build-essential dpkg-cross source=http://ftp.uk.debian.org/debian keyring=debian-archive-keyring suite=unstable
Settings from [General] in the variant would override those in base. (i.e. the value in base is ignored and the variant used instead.) Lists in [General] in the variant will append values from lists in base. Sections in the variant would replace those defined in base, if any. New sections in the variant would be put alongside those in base.
The variant file would need a new config key: Include: /path/ where /path/ is an absolute or relative path to the base config file (relative to the location of the variant config file).
A Variant file could act as a Base file for another config, under the above rules but I won't recommend nesting any deeper than that.
i.e. the cascade starts with the specifics and gets more general. This allows the variant to decide which base files to include, rather than trying to embed logic into a base file that could be included by many variants.
Back to the Emdebian Project homepage.