> * What are best practices to manage private and public keys as well as all these usernames/password for the web ui's? Keys: you should encrypt your private k

> * What are best practices to manage private and public keys as well as all these usernames/password for the web ui's? Keys: you should encrypt your private key with a passphrase. Following one key pair per device account (see other comments) there is not much other management needed. If you get tired of supplying the key passphrase look at using an "SSH agent". Passwords: use a password manager. If your Excel file is encrypted it is perhaps a passable ersatz. * How keep a good overview over all git credentials? GitHub account settings page lists what you have uploaded. On each device, the key pair is in two files under .ssh/ in your home directory for OpenSSH. * Can I store SSH keys in my Excel-File? Yes, just be wary of Excel corrupting the string. However, rarely do you as a human interact with either key information so I do not see the point, other than perhaps as some kind of backup mechanism. I simply leave the SSH key files in place where they were generated by ssh-keygen and used by ssh and/or ssh-agent. * How many SSH keys would you recommended for my scenario? As said in the other comments, I also recommend one key pair per device account with each device account's public key added to each of the relevant GitHub (etc) account. If a particular device account will not access a given remote account, no reason to upload that public key. If SSH is used for other types of access the keys can be shared or there can be reasons to have service-specific keys.