Create Debian sysroots

Introduction

We'll create Debian sysroots suitable for a GCC cross compiler.

Debootstrap machine

Everything below runs on the debootstrap machine as root:

sudo -i

Prerequisites

Debian or Ubuntu or any system that can run debootstrap, with a configured QEMU user emulator. In practice only Debian and Ubuntu will work.

Install debootstrap and associated tools

apt install -y binfmt-support qemu qemu-user-static debootstrap

Run debootstrap

mkdir -p /tmp/sysroots
cd /tmp/sysroots
arches="amd64,x86_64-linux-gnu arm64,aarch64-linux-gnu mips,mips-linux-gnu mips64el,mips64el-linux-gnuabi64 ppc64el,powerpc64le-linux-gnu"
for arch in $arches; do IFS=","; set $arch; qemu-debootstrap --arch "$1" --variant=buildd stable "$2" http://deb.debian.org/debian; unset IFS; done

Fix symlinks

Debootstrap will create absolute symlinks, fix absolute symlinks to refer to the sysroot dir by changing them into relative symlinks.

for arch in $arches; do IFS=","; set $arch; find "$2" -type l -lname '/*' -exec sh -c 'file="$0"; dir=$(dirname "$file"); target=$(readlink "$0"); prefix=$(dirname "$dir" | sed 's@[^/]*@\.\.@g'); newtarget="$prefix$target"; ln -snf $newtarget $file' {} \; ; unset IFS; done

Host machine

Create directories

cd $HOME
arches="x86_64-linux-gnu aarch64-linux-gnu mips-linux-gnu mips64el-linux-gnuabi64 powerpc64le-linux-gnu"
for arch in $arches; do mkdir -p $HOME/cross/sysroot/$arch/{lib,usr/{include,lib}}; done

Copy sysroots

for arch in $arches; do for dir in /lib/ /usr/{include,lib}; do rsync -a ubuntu.local:/tmp/sysroots/$arch/$dir/ $HOME/cross/sysroot/$arch$dir; done; done

Debootstrap machine (again)

Cleanup

Still as root:

rm -rf /tmp/sysroots

See also

• debootstrap
• Debian ports