we will hope you have a clean dualroot env,

to install things apt requires some stuff (here also includes a systemd fix which you will probably need)




#====> Start Out of root
cp /etc/resolv.conf /opt/test/dual_rootfs/etc/resolv.conf
cp /etc/hosts /opt/test/dual_rootfs/etc/hosts
mount --bind /proc /opt/test/dual_rootfs/proc
mount --bind /sys /opt/test/dual_rootfs/sys
mount --bind /dev /opt/test/dual_rootfs/dev
mount --bind /dev/pts /opt/test/dual_rootfs/dev/pts
mount --bind /dev /opt/test/dual_rootfs/dev
mount -t devpts devpts /opt/test/dual_rootfs/dev/pts
mount -t proc proc /opt/test/dual_rootfs/proc
mount -t sysfs sys /opt/test/dual_rootfs/sys
#<= ENTER

echo 'APT::Sandbox::User "root";' > /etc/apt/apt.conf.d/99sandbox #<-------- FIX APT!!



#1. Overwrite failing systemd postinst script with a successful dummy
echo '#!/bin/sh' > /var/lib/dpkg/info/systemd.postinst
echo 'exit 0' >> /var/lib/dpkg/info/systemd.postinst
chmod +x /var/lib/dpkg/info/systemd.postinst

#2. Get a nameserver in there

echo "nameserver 8.8.8.8" > /etc/resolv.conf
echo "nameserver 1.1.1.1" >> /etc/resolv.conf