Errors updating zesty packages - apt update/upgrade

Solution 1:

As described in release notes. Zesty will be supported for 9 months until January 2018. Therefore you can use old-releases site, to install zesty packages.

You can use following sources list entries:

deb http://old-releases.ubuntu.com/ubuntu/ zesty main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ zesty-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ zesty-security main restricted universe multiverse

deb http://old-releases.ubuntu.com/ubuntu/ zesty-proposed main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ zesty-backports main restricted universe multiverse

# this repo is disabled!
#deb http://archive.canonical.com/ubuntu zesty partner

deb-src http://old-releases.ubuntu.com/ubuntu/ zesty main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ zesty-updates main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ zesty-security main restricted universe multiverse

It can be successfully retrieved by apt without any problems.