sudo apt-get -y install ntp
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/n/ntp/ntp_4.2.8p4+dfsg-3ubuntu5.3_amd64.deb  404  Not Found

ntp:amd64 (1:4.2.8p4+dfsg-3ubuntu5.5), libopts25:amd64 (1:5.18.7-3, automatic)

Preparing to unpack .../ntp_1%3a4.2.8p4+dfsg-3ubuntu5.5_amd64.deb ...
Unpacking ntp (1:4.2.8p4+dfsg-3ubuntu5.5) ...