Tag: ssh

About

Secure Shell or SSH is a network protocol that allows data to be exchanged over a secure channel between two computers. Encryption provides confidentiality and integrity of data. SSH uses public-key cryptography to authenticate the remote computer and allow the remote computer to authenticate the user, if necessary.

SSH is typically used to log into a remote machine and execute commands, but it also supports tunneling, forwarding arbitrary TCP ports and X11 connections; it can transfer files using the associated SFTP or SCP protocols.

An SSH server, by default, listens on the standard TCP port 22. An ssh client program is typically used for establishing connections to an sshd daemon accepting remote connections. Both are commonly present on most modern operating systems, including Microsoft Windows, Mac OS X, Linux, Solaris and OpenVMS. Proprietary, freeware and open source versions of various levels of complexity and completeness exist.

From en.wikipedia.org/wiki/Secure_Shell

 

Login automatically with SSH keys

With SSH you can securely login to any Linux server and execute commands remotely. You can even use SSH to transfer and synchronize files from one server to another. Automating these tasks can make your life easier, but normally SSH prevents that because it requires you to login every time. Well, not anymore, in this article I will show you how to connect to SSH without a password.

Synchronize files with rsync

Synchronizing files from one server to another is quite awesome. You can use it for backups, for keeping web servers in sync, and much more. It's fast and it doesn't take up as much bandwidth as normal copying would. And the best thing is, it can be done with only 1 command. Welcome to the wonderful world of rsync.

Block brute force attacks with iptables

Since 2005 there has been an immense increase in brute force SSH attacks and though Linux is pretty secure by default, it does not stop evil programs from indefinitely trying to login with different passwords. Without proper protection your server is a sitting duck waiting for a bot to guess the right combination and hit the jackpot. But with just 2 commands we can stop that.

Make SSH connections with PHP

Not everyone knows about PHP's capabilities of making SSH connections and executing remote commands, but it can be very useful. I've been using it a lot in PHP CLI applications that I run from cronjobs, but initially it was a pain to get it to work. The PHP manual on Secure Shell2 Functions is not very practice or thorough for that matter, so I would like to share my knowledge in this how to, to make it a little less time consuming setting this up.