What To Do: Users Still Wants Telnet

Posted on in Categories CentOS, fedora linux, GNU/Open source, High performance computing, Howto, Linux, package management, RedHat/Fedora Linux, Security, Ubuntu Linux, UNIX last updated August 26, 2008

TELNET (TELecommunication NETwork) is a network protocol used on the Internet or local area network (LAN) connections. It was developed in late 60s with RFC 15. Telnet is pretty old for login into remote system and it has serious security problem. Most admins will recommend using Open SSH (secure shell) for all remote activities. But you may find users who are still demanding telnet over ssh as they are comfortable with Telnet. Some users got scripts written in 90s and they don’t want to change it. So what do you do when users demands telnet?

OpenSSH Tip: Check Syntax Errors before Restarting SSHD Server

Posted on in Categories Linux, Networking, OpenBSD, RedHat/Fedora Linux, Security, Sys admin, Tips, Troubleshooting, UNIX last updated June 17, 2017
OpenSSH - SSHD Logo

OOpenSSH (OpenBSD Secure Shell) is a default secure shell for encrypted communication sessions over a computer network using the ssh protocol. Usually, you log in using ssh and makes changes to its configuration file /etc/ssh/sshd_conf over a remote session. If there is an error in configuration, the server may not start (i.e. no remote login allowed). This will result in a disaster; if you didn’t have access to the remote console. But how do you find out a syntax error for the sshd_config file?
Continue reading “OpenSSH Tip: Check Syntax Errors before Restarting SSHD Server”

Howto Use SSH To Run Command On A Remote Machine

Posted on in Categories Automation, CentOS, Debian Linux, FreeBSD, Gentoo Linux, High performance computing, Howto, Linux, Shell scripting, Sys admin, Tuning, Ubuntu Linux, UNIX last updated August 17, 2007

This article examined a simple, but powerful, method to run commands on a remote machine using combination of ssh and a shell script:

Use Secure Shell (SSH) to run commands on remote UNIX systems and, with some simple scripts, put together a system that enables you to manage many systems simultaneously from one machine without having to log in directly to the machines themselves. Also examine the basics of a distributed management system and some scripts and solutions using the technique.

I have already covered how to execute commands on multiple Linux or UNIX servers via a shell script. The disadvantage of shell script is commands do not run in parallel on all servers. However, several tools exist to automate this procedure in parallel. With the help of tool called tentakel (highly recommended) , you run distributed command execution. Also, you can execute commands on multiple Linux or UNIX servers using special tools such as multixterm from expect project.

=> Distributed administration using SSH

Linux Creating virtual private networks (VPN) with tsocks and VTun tools

Posted on in Categories Linux, Networking, Security last updated June 14, 2006

irtual private networks (VPN) let remote users connect back to corporate networks over encrypted links. Many VPNs are built with proprietary technology and can be tricky and expensive to set up. For a small business or an individual who needs a simple way to securely access remote networks, setting up a true VPN might be prohibitively expensive in terms of both money and time. Let’s look at two simple approaches that bring you transparency without the cost. All you need is Secure Shell (SSH) access to a server on the network you’re trying to access.