1.d Access remote systems using SSH...
The SSH protocol...
The SSH protocol uses encryption to secure the connection between a client and a server. All user authentication, commands, output, and file transfers are encrypted to protect against attacks in the network.
The new protocol replaced several legacy tools and protocols, including telnet, ftp, FTP/S, rlogin, rsh, and rcp.
Old Technologies that the SSH stack replaces
- Telnet -> SSH
- RCP -> SCP
- FTP -> SFTP
Usage...
SSH is typically used to log into a remote machine and execute commands, but it also can transfer files using the associated SSH file transfer (SFTP) or secure copy (SCP) protocols. SSH uses the client-server model.
Basic Syntax...
To connect to a remote system using SSH, we’ll use the ssh command. The most basic form of the command is:
ssh remote_host
The remote_host in this example is the IP address or domain name that you are trying to connect to.
This command assumes that your username on the remote system is the same as your username on your local system.
If your username is different on the remote system, you can specify it by using this syntax:
ssh remote_username@remote_host
Once you have connected to the server, you may be asked to verify your identity by providing a password.
Important command flags/options
-l- login-i- specify a private key to use-F- specify config file-X- enable X forwarding
Configuration Files...
Client Config files
~/.ssh/config/etc/ssh/ssh_config
Server config file
/etc/ssh/sshd_config
Other Important SSH Commands...
We will review these later.
ssh-keygenssh-copy-id(note that this is a script and not a binary)
How to enable commonly used config...
The listed configuration is done at the server: /etc/ssh/sshd_config.
- X11 forwarding
X11Forwarding yes
- sftp subsytem
Subsystem sftp /usr/lib/ssh/sftp-server
- Root login
PermitRootLogin yes
- Password authentication
PasswordAuthentication yes