SSH - Configuration

About

There are two different sets of configuration files:

• those for client programs (that is, ssh, scp, and sftp),
• and those for the server (the sshd daemon).

Configuration Type

User / Client

For the open ssh client: ssh_config

• on a user scope

$HOME/.ssh/config

• for the system

/etc/ssh/ssh_config
# options may be specified in files in the .d directory 
# and override the central ssh_config file
/etc/ssh/ssh_config.d/*.conf

Example:

# Restricts the declarations (up to the next Host or Match keyword)
Host github*
    Hostname github.com
    # Specifies a file from which the user's identity key is read when using public key authentication. 
    IdentityFile ~/.ssh/id_rsa.github
    IdentitiesOnly yes
    AddKeysToAgent yes

System / Daemon (Sshd)

See What is sshd, the OpenSSH Server?