Common/standard folders/files for SSH:
There are two folders, one is /etc/ssh, the other is ~/.ssh
You can easily tell that etc/ssh is for hostwide, while ~/.ssh is for user wide.
Here is SSH configuration data parsing order:
# Configuration data is parsed as follows:
# 1. command line options
# 2. user-specific file
# 3. system-wide file
User SSH files are stored in "~/.ssh"
The tilde ~ is an alias for the user home folder, e.g., /home/<your username>
SSH host wide files
/etc/ssh/sshd_config ssh daemon configuration file
SSH config file
~/.ssh/config or /etc/ssh/ssh_config
ssh session configuration
SSH private key filename
~/.ssh/id_dsa SSH2 private key file
~/.ssh/id_rsa SSH private key file
SSH public key filename
The public key filename is the private key filename with .pub as the extension.
For how to use private/public key pair, see how to setup SSH passphrase free access
Stored server figerprints file
Stored (known) server fingerprints are written to known_hosts
This is used to detect "man in the middle" attacks. If the host fingerprint changes, SSH will report an error.
Authorized key file
The file authorized_keys is used to store public keys. Used to allow the user to maintain a collection of identity keys in one place (easier to backup and restore). The authorized_keys file is a collection of public keys, created by simply echoing out (cat) the contents of a public key, appending it to the bottom of the existing authorized_keys file.
SSH keys must have 600 or more restrictive permissions in place
If permissions are too open, SSH will report an error and refuse to run until you correct the security problem.
Other identifity files
You can generate multiple identifity files for different remote hosts/purposes, naming them as you want, then following the instruction Config multiple ssh identies on one client