glibc in Ubuntu 16.04 does have MIN_KERNEL_SUPPORTED := 2.6.32 in debian/sysdeps/amd64.mk precisely to support running Ubuntu userspace on RHEL6 kernels. This is not a supported configuration for a full booted Ubuntu 16.04 install, because the minimum kernel version for udev itself is higher than this (iirc, Linux 3.2) - but since this is running as a container, udev isn't a concern.
So it seems reasonablbe to expect this not to regress as part of a security update of systemd on Ubuntu 16.04.
glibc in Ubuntu 16.04 does have MIN_KERNEL_ SUPPORTED := 2.6.32 in debian/ sysdeps/ amd64.mk precisely to support running Ubuntu userspace on RHEL6 kernels. This is not a supported configuration for a full booted Ubuntu 16.04 install, because the minimum kernel version for udev itself is higher than this (iirc, Linux 3.2) - but since this is running as a container, udev isn't a concern.
So it seems reasonablbe to expect this not to regress as part of a security update of systemd on Ubuntu 16.04.