If you remove
gnome-keyring from Ubuntu 16 (Xenial),
ssh-agent should then
start and work properly with no further changes.
sudo apt-get remove gnome-keyring
echo gnome-keyring hold | sudo dpkg --set-selections
The second line is to stop the package being reinstalled without you asking for it.
When I upgraded from Ubuntu 14.04 LTS (Trusty Tahr) to Ubuntu 16.04 LTS
(Xenial Xerus), I lost any functioning ssh agent. On 14, I was using
gnome-keyring, but that stopped working after upgrade.
gnome-keyring was running, but not prompting for ssh
ssh-agent was not being started at all. It looked like I could
gnome-keyring (maybe need to enable ssh module?) or start and use
ssh-agent instead. It seemed
ssh-agent was configured to run already,
however it still was not started. Maybe it’s configured not to start if you use
ssh-agent seems to be the better choice anyway, for various reasons,
gnome-keyring does not support ed25519 keys.