89 lines
3.8 KiB
Text
89 lines
3.8 KiB
Text
Polystrap is a tool to create a foreign architecture rootfs without
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needing superuser privileges by using multistrap, fakeroot, fakechroot
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and qemu user mode emulation from the qemu-user-static package.
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The proper qemu-*-static binary must be properly configured
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(eg. /etc/qemu-binfmt/arm pointing to /usr/arm-linux-gnueabi/ with
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xapt-installed libc and possibly other packages); package
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binfmt-support (which is only a "Recommends" of qemu-user-static) must
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also be installed.
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While I wanted to build without superuser privileges, multistrap would never
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offer mechanisms that would allow me to do so. Hence I wrote this script which
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wraps multistrap. Since I wanted to keep it as simple as possible, a fully
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functional polystrap will need nothing more than a multistrap.conf, a hooks
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directory and a rootfs tree skeleton. Stuff like packages directory, and config
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file are optional and can be replaced by editing multistrap.conf and passing
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commandline options. Without comments the scripts is currently around 120 lines
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and I have no intention to make it much more complex.
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Polystrap is invoked as such:
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./polystrap.sh PLATFORM
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PLATFORM is a directory that at least contains a multistrap.conf. The
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multistrap.conf may contain variables from polystrap.sh.
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In the normal case PLATFORM will contain some additional bits.
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PLATFORM/config - A file that is sourced by ./polystrap.sh and
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contains variable declarations like:
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SUITE - stable, testing, unstable
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ARCH - armel, armhf, amd64, i386
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ROOTDIR - where the rootfs is created
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MIRROR - debian mirror to use for packages
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The file is not strictly needed because the options
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can also be set by commandline arguments and the
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script will fall back to ./default/config.
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Correct settings for ARCH and ROOTDIR are necessary
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for proper operation, whereas other parameters are
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only used if your multistrap.conf references them.
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PLATFORM/debconfseed.txt - as the name suggests
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PLATFORM/hooks - A directory that contains files that are sourced by
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polystrap after packages are installed.
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PLATFORM/packages - Contains files with one debian package per line.
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Grouping packages by that allows easier selection.
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PLATFORM/root - Contains a rootfs tree that is copied to the target
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directory after packages are unpacked by multistrap.
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Reasonable examples of how those pieces look like can be found in the defaults
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directory.
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Everything from the PLATFORM/config file can be overwritten by commandline
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options:
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-s suite
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-a arch
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-d rootdir
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-m mirror
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Additionally the following option allows to specify a list of packages that is
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then used instead of the contents of the PLATFORM/packages directory:
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-p packages
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How the script works:
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*) re-execute itself in fakeroot
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*) source default/config
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*) source PLATFORM/config
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*) determine package selection by PLATFORM/packages or commandline argument
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*) create multistrap.conf in /tmp from PLATFORM/multistrap.conf
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*) run multistrap
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*) copy contents of PLATFORM/root
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*) copy qemu usermode binary
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*) set debconf selections
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*) run preinst scripts
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*) configure packages
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*) source PLATFORM/hooks
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*) cleanup
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*) generate tarball
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When creating a directory for a new target one can either just copy the defaut
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directory or use the ./newtarget.sh script which will use symlinks where it
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makes sense, will not copy the whole package selection and will set hostname
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according to the target name.
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Example config and multistrap.conf for usage of armhf is given in the default
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directory as config.armhf and multistrap.conf.armhf. Some fakechroot bugs
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(#611156) is unfortunately blocking this functionality right now.
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