Comment 4 for bug 1652622

fstrim.service in Xenial is in examples/

What we could do is modify the fstrim script in cron.weekly to something along those lines:

#!/bin/sh
# trim all mounted file systems which support it
+if ! /usr/bin/systemd-detect-virt -q -c; then
/sbin/fstrim --all || true
+ fi

at least the cron.weekly won't try to start fstrim inside a container automatically every sunday-ish IIRC.