Comment 20 for bug 1618572

trusty + linux-virtual-lts-xenial looks good also.

ubuntu@sm-y1:~$ uname -r
4.4.0-38-generic
ubuntu@sm-y1:~$ dpkg -S /boot/vmlinuz-$(uname -r)
linux-image-4.4.0-38-generic: /boot/vmlinuz-4.4.0-38-generic
ubuntu@sm-y1:~$ grep overlay /proc/mounts
overlayroot / overlayfs rw,relatime,lowerdir=/media/root-ro,upperdir=/media/root
-rw//overlay,workdir=/media/root-rw//overlay-workdir 0 0
ubuntu@sm-y1:~$ lsb_release -sc
trusty

$ dpkg-query --show | grep linux- | grep -v headers
linux-image-3.13.0-95-generic 3.13.0-95.142
linux-image-3.13.0-96-generic 3.13.0-96.143
linux-image-4.4.0-36-generic 4.4.0-36.55~14.04.1
linux-image-4.4.0-38-generic 4.4.0-38.57~14.04.1
linux-image-virtual 3.13.0.96.104
linux-image-virtual-lts-xenial 4.4.0.38.28
linux-virtual 3.13.0.96.104
linux-virtual-lts-xenial 4.4.0.38.28

$ sudo apt-key add my.pubkey
OK