Can't use SSH on the standard port 22? Need to tunnel through a proxy server? Work behind a draconian firewall and can't SSH directly? No problem. This document will hopefully show you how to tunnel through an http-proxy server without any server-side modifications.
Build and Configure an HTTP-Proxy Application
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Get Corkscrew: available from corkscrew home page.
Under Debian Linux ( and most other distros) startup files are stored in /etc/init.d/ directory and symbolic linked between /etc/rcX.d/ directory exists. Debian Linux (Red Hat/ Fedora) uses System V initialization scripts to start services at boot time from /etc/rcX.d/ directory. Debian Linux comes with different utilities to remove unwanted startup file:
(A) rcconf
It is a console based interactive utility that allows you to control which services are started when the system boots up or reboots. It displays a menu of all the services which could be started at boot. The ones that are configured to do so are marked and you can toggle individual services on and off. To start rconf, login as root user and type rcconf
# rcconf
In this article I'll show you some simple tricks to help you tighten security for your secure shell (SSH) service.
The SSH server configuration file is located in /etc/ssh/sshd_conf. You need to restart the SSH service after every change you make to that file in order for changes to take effect.
Change SSH listening port
By default, SSH listens for connections on port 22. Attackers use port scanner software to see whether hosts are running an SSH service. It's wise to change the SSH port to a number higher than 1024 because most port scanners (including nmap) by default don't scan high ports.
Open the /etc/ssh/sshd_config file and look for the line that says:
Port 22
Change the port number and restart the SSH service:
First install the following on a base installation of centos 5.4
yum -y update
yum groupinstall core
yum groupinstall base
Setup Squid proxy as a transparent server.
Main benefit of setting transparent proxy is you do not have to setup up individual browsers to work with proxies.
My Setup:
i) System: HP dual Xeon CPU system with 8 GB RAM (good for squid).
ii) Eth0: IP:192.168.1.1
iii) Eth1: IP: 192.168.2.1 (192.168.2.0/24 network (around 150 windows XP systems))
iv) OS: Red Hat Enterprise Linux 4.0 (Following instruction should work with Debian and all other Linux distros)
Here are the steps required to successfully install zimbra 4.5 on CentOS5. The system will work perfectly even after its rebooted (no MTA errors). I have used these steps to install zimbra on three servers and all work perfectly. I hope this guide will save others the time of hunting around forums. Also it’s a good idea to have the A records and MX records setup before you start the installation.
1. Install Centos5 from DVD or CDROM configure the entire disk
2. Configure your Fully Qualified Hostname, IP address and Gateway, DNS details
Sudo can be configured to to send e-mail when the sudo command is used. Open /etc/sudoers file, enter:
# vi /etc/sudoers
Configure alter email id:
mailto "admin@staff.example.com"
mail_always on
Where,
One of the few things I missed when I made my move from Linux to OSX is the ability to use htop. As many of you might know, OSX is based on Mach Kernel – a custom implementation of Unix. So right out of the box OSX gives you the power of many *nix command line tools, which is why users who are comfortable with *nix systems, fit right at home with OSX.
Need to monitor Linux server performance? Try these built-in command and a few add-on tools. Most Linux distributions are equipped with tons of monitoring. These tools provide metrics which can be used to get information about system activities. You can use these tools to find the possible causes of a performance problem. The commands discussed below are some of the most basic commands when it comes to system analysis and debugging server issues such as:
I am on Red Hat Enterprise Linux 5.x server. Is there is an easy way to run script or command at boot time after fresh reboot command?
crontab is the program used to install, deinstall or list the tables used to drive the cron daemon in Vixie Cron. Each user can have their own crontab, and though these are files in /var/spool/cron/crontabs, they are not intended to be edited directly. You or user can use crontab program to edit cron jobs.