I'm new in Ubuntu 16 and want to know, how to fix this problem.
Reading package lists... Done
Building dependency tree
Reading state information... Done
4 packages can be upgraded. Run 'apt list --upgradable' to see them.
W: http://archive.canonical.com/dists/precise/Release.gpg: Signature by key 630239CC130E1A7FD81A27B140976EAF437D05B5 uses weak digest algorithm (SHA1)
W:
are just warnings. You can still run your upgrades as normal. That warning is just that whatever site you are connecting to has a weak digest algorithm that whoever owns it needs to update it. – Terrance May 18 '17 at 03:53