Machine variants

emsandbox supports a set of customisation routines for each combination of machine and variant, allowing the rootfs to be customised to specific variants of a specific machine. Configuration data is stored in the machine subdirectory of your Emdebian work directory. Using the -m option to emsandbox loads packages.conf from the $WORK/machine/$MACHINE/default subdirectory prior to starting debootstrap. Once the first stage install is complete, emsandbox calls setup.sh from the same directory, passing the location and architecture of the tarball, so that other fine tuning can take place prior to creating the tarball. At this stage, any operations inside the rootfs must not try to execute any binaries within the rootfs. Immediately before creating the tarball, config.sh is copied into the /machine/$MACHINE/default/ directory of the rootfs, ready to be called when emsecondstage has completed the second stage of the debootstrap process.

Skeleton versions of packages.conf, setup.sh and config.sh are available in /usr/share/emdebian-tools/machine/.

packages.conf is intended to be the principal place for adjusting the emsandbox tarball to suit the needs of specific machine variants. setup.sh and config.sh can fine tune the results but in order to avoid reinventing the wheel, if more than a few machines need similar adjustments to the same files, future versions of packages.conf will collate those into a single configuration parameter available to all.

packages.conf supports:

INCLUDE

Add a comma separated list of package names to the list of packages added to the tarball and installed in the second stage. Currently, debootstrap has problems with multiple repositories so either upload this package to the same repository as your other packages or create an apt-proxy that can serve as a local repository, set it in PROXY and specify a usable mirror for the device in MIRROR.

debootstrap can sometimes fail to pick up deeper dependencies of included packages. Check the output of debootstrap during the emsandbox logs and ensure that all the dependencies needed by your included packages are actually downloaded. It may be easier to customise /usr/lib/emdebian-tools/emdebian.crossd and pass that to the SCRIPT parameter in this file. If there are a lot of extra packages it is probably best to use a new script anyway so that the script can produce useful output instead of appearing to stall.

DEFAULT: empty

SCRIPT

Overrides the default emsandbox suite-script that debootstrap uses to determine the base and required packages and the all important sequence in which the packages can be installed. SCRIPT can be overridden on the emsandbox command line.

DEFAULT: /usr/lib/emdebian-tools/emdebian.crossd

MIRROR

Overrides the default emsandbox mirror. This repository will be set in /etc/apt/sources.list and will also be used by debootstrap to obtain all packages for the tarball unless PROXY is also set.

DEFAULT: http://buildd.emdebian.org/emdebian/

PROXY

Specifies a separate repository to pass to debootstrap that may be local or otherwise not intended for use once the tarball is installed. Use MIRROR to set the same value in debootstrap and /etc/apt/sources.list. If PROXY is specified without MIRROR, the default emsandbox MIRROR (http://buildd.emdebian.org/emdebian/) will be written into /etc/apt/sources.list.

DEFAULT: empty

TARBALL_NAME

Overrides the default name (emdebian-$ARCH) of the tarball. Do not specify a path here, just a filename with the .tgz suffix.

DEFAULT: emdebian-$ARCH.tgz where $ARCH is specified to emsandbox or as the dpkg-cross default architecture.

SUITE

Not recommended to be changed.

DEFAULT: unstable

Due to limitations in the current debootstrap support, the only way of adding packages to the first stage is by providing a customised suite script. Even if emsandbox migrates to using a tool from Stag to overcome shortcomings in debootstrap, support for packages.conf, setup.sh and config.sh will remain.

Automating rootfs builds

This snippet demonstrates a possible method of automating the builds of rootfs packages - what is lacking is any ability to detect which packages do not need a rebuild. This functionality is available in the emtargetcmp script in emdebian-tools (>= 0.4.3) so it should be possible to merge this perl code with the snippet and then merge into an autobuilding mechanism such as wanna-build.

try_autobuild()
{
    . /usr/lib/debootstrap/functions
    SCRIPT=/usr/lib/emdebian-tools/emdebian.crossd
    . $SCRIPT
    work_out_debs
    requiredX=$(echo $(echo $required | tr ' ' '\n' | sort | uniq))
    baseX=$(echo $(echo $base | tr ' ' '\n' | sort | uniq))
    echo "Trying to automate rebuilds of rootfs packages:"
    echo $requiredX $baseX | fold -s
    if [ -z $sources ]; then
        echo "$PROG: no source list found in $SCRIPT"
    fi
    sourcesX=$(echo $(echo $sources | tr ' ' '\n' | sort | uniq))
    for pkg in $sourcesX; do
        src=`apt-cache showsrc $pkg | grep Package`
           emsource -b $pkg
    done
}

SHELL variables

Note that the Debian chroot program from coreutils expects you to want the same shell outside the chroot as you want to use inside the chroot. The typical Debian default shell in /etc/passwd is bash which is not present in the Emdebian rootfs so chroot needs the /bin/sh option.