Can an ssh pass phrase added after ssh is already setup? I'm using Debian 8 stable Jessie 8.7. And how can you save it in Debian like in a keyring so you do not have to enter it everytime? Thanks to all for the answers.
SSH uses your normal user password, so it can be changed with the
passwd command on the machine you're connecting to.
By default, Debian has public/private key authentication enabled, so you can use RSA keys instead of a passphrase, if you put your public key on the system you're connecting to. First, you need to create a key on your local machine:
Then, put it on the remote server. Type this command on your local machine:
cat ~/.ssh/id_rsa.pub | ssh user@remotehost "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"
Then you will no longer need a password to log in.
EDIT: @EEAA brings up a good point:
ed25519 is a much better cryptographic system nowadays than
RSA, and it might be a good idea to start switching. You can create an
ed25519 public/private key pair and copy it to your remote system like so:
ssh-keygen -t ed25519 cat ~/.ssh/id_ed25519.pub | ssh user@remotehost "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"
There's an interesting read regarding ed25519 vs RSA over in the StackExchange IS community