Linux and other Unix-like operating systems use the term “swap” to describe both the act of moving memory pages between RAM and disk, and the region of a disk the pages are stored on. It is common to use a whole partition of a hard disk for swapping. However, with the 2.6 Linux kernel, swap files are just as fast as swap partitions. Now, many admins (both Windows and Linux/UNIX) follow an old rule of thumb that your swap partition should be twice the size of your main system RAM. Let us say I’ve 32GB RAM, should I set swap space to 64 GB? Is 64 GB of swap space really required? How big should your Linux / UNIX swap space be?

A rootkit is a program designed to take fundamental control of a computer system, without authorization by the system’s owners and legitimate managers.

Most rootkits use the power of the kernel to hide themselves, they are only visible from within the kernel. How do I detect rootkits under CentOS or Debian Linux server?

Linux Detecting / Checking Rootkits with Chkrootkit and rkhunter Software

Internet SCSI (iSCSI) is a network protocol that allows you to use of the SCSI protocol over TCP/IP networks. It is good alternative to Fibre Channel-based SANs. You can easily manage, mount and format iSCSI Volume under Linux. It allows access to SAN storage over Ethernet. Open-iSCSI project is a high-performance, transport independent, multi-platform implementation of iSCSI. Open-iSCSI is partitioned into user and kernel parts.

The iscsi package provides the server daemon for the iSCSI protocol, as well as the utility programs used to manage it. iSCSI is a protocol for distributed disk access using SCSI commands sent over Internet Protocol networks. This package is available under Redhat Enterprise Linux / CentOS / Fedora Linux and can be installed using yum / apt-get command.

netcat utility (nc command) considered as TCP/IP swiss army knife. It reads and writes data across network connections, using TCP or UDP protocol. It is designed to be a reliable “back-end” tool that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich network debugging and exploration tool, since it can create almost any kind of connection you would need and has several interesting built-in capabilities.

This howto explain migrating data between two server hard drives using netcat over a network. It is very easy to copy complete drive image from one server to another.

With this tip you will be able to work from home using VPN and that too from Linux / FreeBSD system for the proprietary Microsoft Point-to-Point vpn server.

Different organization uses different VPN connection options such as SSL, PPTP or IPSEC. When you need to access corporate network and its services, you need to login using VPN.

The Point-to-Point Tunneling Protocol (PPTP) is a method for implementing virtual private networks. It works on Data link layer (#2 layer) on TCP/IP model. Personally I prefer IPSEC. PPTP Client is a Linux, FreeBSD, NetBSD and OpenBSD client for the proprietary Microsoft Point-to-Point Tunneling Protocol, PPTP. Allows connection to a PPTP based Virtual Private Network (VPN) as used by employers and some cable and ADSL internet service providers.