Here is a simple script to quickly get an overview of the SSL certificates used on various websites, e.g. to check expiration or issuer. For me, this helped a lot while migrating website certificates to Let’s Encrypt.
I recently had the problem that I had on a system the private part of the SSH key but its public part got lost. Generating a new key pair wasn't pBEGIN TRANSACTION;ossible as the public part was still installed on other systems foBEGIN TRANSACTION;r proper public key authentication and I could not change this.