ssh stands for secure shell. It allows for a remote connection to a machine over TCP.
ssh username@host
The default port is 22.
The normal way to use ssh is to have a public/private key pair shared between client and host. E.g., the client generates a public private key pair via the following
ssh-keygen: Generating a public/private key pair
ssh-keygen -t rsa -b 4096 -C "your_email@example.com"
This uses OpenSSH to generate a machine-local public-private key pair. -t specifies the type of key generated, -b the bitsize, and -C adds a comment, which can help you differentiate between multiple keys.
ssh-agent + ssh-add: Using the key pair
Next you should set up your ssh-agent, which is a service/daemon that runs in the background on your local machine. It manages your private keys and uses them for authenticating. You add a key with ssh-add.
with them makes them available to requesting remote services. This service will be available for when remote services want to validate that you are who you say you are. I don't understand it very well, but the two steps are 1, make sure it's running, and 2, add your newly generated private key to it.
eval "$(ssh-agent -s)"
ssh-add ~/.ssh/id_rsa
The output of ssh-agent -s is quite straightforward. It is setting (and also creating(?)) env vars that are discoverable by the ssh client when trying to check your keys.
Adding a hostname to your ssh
On the machine you are connecting from you can edit ~/.ssh/config to include a hostname with your required IP address, thereby allowing you to write ssh aeg instead of ssh root@123.123.123.123.
For example, in you could add something like this in ~/.ssh/config file, include the following:
Host aeg
HostName 123.123.123.123
User root
Now you can connect with ssh aeg instead of ssh root@123.123.123.123.