I installed libpam-pwquality:sudo apt-get install libpam-pwqualityAnd configured /etc/pam.d/common-password:password        requisite                       pam_pwquality.so retry=3 minlen=10password        [success=1 default=ignore]      pam_unix.so obscure use_authtok try_first_pass sha512password        required                        pam_deny.sopassword        required                        pam_permit.soThen when I ran passwd, I could still set a password of 2 or 3 characters. What was missing?
libpam-pwquality not working in Ubuntu 16.04
pam