Battling with SSH, cron jobs, and macOS Keyring

So today, I was setting up a cronjob on my trusty MacBook Pro. The goal was to backup some folders from a remote Linux server via rsync. The script is simple. It goes something like this: rsync -avz -e "ssh -i ~/.ssh/my_rsa_keyfile" myuser@myserver:remotedir/ ~/localdir/ Launched by hand, it works seamlessly. Call it from a cron job via crontab, and I get a permission denied error. I then enabled ssh -v option to gather a little intel on what was actually going on. »