Mandating key-based logins with sshd

This page provides a pretty good summary of creating a public/private key pair on the client and adding the public key to the server's authorized_keys file.

On the server side, edit /etc/ssh/sshd_config and add the directive PasswordAuthentication no and then restart sshd with sudo /etc/init.d/ssh restart Anyone that tries to log in to your server without a public key in the server's authorized_keys file will now not even be given the chance to enter a password.

sshd_config manpage

Keep SSH connections from timing out, client-side

Put these lines in ~/.ssh/config

ServerAliveInterval 300
TCPKeepAlive yes

OpenSSH Installation, SCP, SFTP

Installation of OpenSSH was a breeze. Just one command from Breezy Badger (Ubuntu 5.10) server installed it on my server: apt-get install openssh-server. Now I can administer my box from anywhere! Yay! (provided, of course, no power outages, etc...)

To SSH into a server: ssh <username>@<ip address>

To upload a directory recursively (with encryption... blowfish is an encryption algorithm and scp stands for secure copy protocol, a utility available on almost all UNIX-derived machines): scp [-c blowfish] -r <source path> <username>@<target ip address>:<target path> To download over scp, switch the source and target.

For example, to upload from your music collection: scp -r /home/<username>/Desktop/Musical/Music/Depeche\ Mode/ <username>@<server address>:/home/<username>/Musical/Music/

And to do the opposite (download a directory from the server, in this example to the current directory): scp -r <username>@<server address>:/home/<username>/Musical/ .

Another option is sftp which can perform ftp-like operations (including interactive sessions) over an ssh connection.

Links:

• OpenSSH web site: http://www.openssh.com/
• Wikipedia SFTP article: http://en.wikipedia.org/wiki/SSH_file_transfer_protocol
• Wikipedia SSH article: http://en.wikipedia.org/wiki/SSH
• Wikipedia SCP article: http://en.wikipedia.org/wiki/Secure_copy
  

Manpages:

• SFTP manpage: http://www.eos.ncsu.edu/remoteaccess/man/sftp.html
• SCP manpage: http://www.linuxcommand.org/man_pages/scp1.html
• SSH manpage: http://www.eos.ncsu.edu/remoteaccess/man/ssh.html