Working with squashfs:
Say I want to update the templated policy on the device:
$ mkdir /tmp/overlay /tmp/work
$ sudo mount -t overlayfs -o lowerdir=/usr/share,upperdir=/tmp/overlay,workdir=/tmp/work overlayfs /usr/share
$ sudo dpkg-deb -x ./tmp/ubuntu-core-security-seccomp_16.04.10_all.deb /
$ sudo dpkg-deb -x ./tmp/ubuntu-core-security-apparmor_16.04.10_all.deb /