SSH

SSH (Secure Shell) is the standard method to securely connect to remote Linux servers. It encrypts all communication, preventing eavesdropping or tampering.

By default, SSH runs a server process listening on port 22 on the remote machine. To connect, simply run:

ssh user@remote-server

If one omit the username, SSH assumes the local username.

Passwordless Authentication with SSH Keys

For convenience and security, passwordless login is preferred. This uses a key pair:

• Generate a key pair on local machine:

  ssh-keygen -t rsa

• Copy the public key to the remote server:

  ssh-copy-id user@remote-server

Once done, the public key is added to the remote server’s ~/.ssh/authorized_keys file, allowing the user to login without typing the password.

SCP — Secure Copy Over SSH

SCP uses the SSH protocol to securely transfer files between local and remote systems.

To copy a local file to a remote server:

scp /path/to/local/file user@server:/path/to/destination/

For directories, use the recursive flag:

scp -r /local/directory user@server:/remote/path/

To preserve file permissions and timestamps during copy, add:

scp -p /local/file user@server:/remote/path/