Setting up a RootFS

For AArch64 hosts you are required to have an x86-64 rootfs. With or without 32bit compatibility libraries.

This isn't strictly required for testing on x86-64 host environments but is useful for ensuring correct behaviour there.

Prereqs

An x86-64 PC OR qemu for chrooting

Getting Started

The easiest way to get started is to just download a prebuilt x86-64 rootfs from your favourite distribution and extract it to where you want.

Ubuntu - http://cdimage.ubuntu.com/ubuntu-base/releases/
Debian Debootstrap guide - https://wiki.debian.org/Debootstrap

Using chroot you can then enter the rootfs and install applications that you desire for testing purposes

Cross architecture chroot

If you don't have binfmt_misc setup to run x86/x86-64 binaries on your AArch64 host, then you need to install and copy over qemu-static to the rootfs.

sudo apt-get install qemu-user-static
cp /usr/bin/qemu-x86_64-static ${ROOTFS}/usr/bin/
sudo chroot ubuntu_rootfs qemu-x86_64-static /bin/bash

Additional TmpFS folders

Depending on what you're doing in the chroot, you may need or want some tmpfs folders that applications are expecting

sudo mount -t proc /proc ${ROOTFS}/proc/
sudo mount --rbind --make-rslave /sys ${ROOTFS}/sys/
sudo mount --rbind --make-rslave /dev ${ROOTFS}/dev/

You may or may not need another /dev/pts location as as well

sudo mount --rbind --make-rslave /dev/pts ${ROOTFS}/dev/pts/

Then of course, make sure to unmount these partitions when you're done

sudo umount ${ROOTFS}/proc/
sudo umount -R ${ROOTFS}/sys/
sudo umount -R ${ROOTFS}/dev/
sudo umount -R ${ROOTFS}/dev/pts/

Additional Steps

Running under WSL1

/etc/hosts and /etc/resolv.conf change on the host side. You'll need to copy those over to the rootfs if you want network functionality to work.

Ubuntu rootfs bad ld link

Ubuntu has a link at /lib64/x86_64-linux-gnu/ld-linux-x86-64.so.2 that is an absolute path link to /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2. This link needs to be changed to a relative link to the ld-linux-x86-64.so.2 link in the same /lib64 directory

cd ${ROOTFS}
ln -s -f ../../usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 lib64/

Ubuntu packages to install

Sample packages to install in the rootfs

apt-get install pulseaudio libgles1 libgles2 libglx-mesa0 libgl1-mesa-dri libgl1-mesa-glx mesa-utils mesa-utils-extra

Pulseaudio specifically is required so pulseaudio will work when talking to the host pulseaudio

Development:Setting up RootFS

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