Unix Commands

How to find number of processors in linux $cat /proc/cpuinfo | grep processor processor : 0 processor : 1 It has two logical processors $cat /proc/cpuinfo|grep physical physical id : 0 physical id : 0 It has single physical processor Processor: Intel dual core Janu

Why do I need so many IP addresses to set up fault tolerance? There are three 'classes' of IP addresses that we use: 1) 'Front-end' IP addresses - think of these as what are the current IP addresses of each of the Load Balancer machines. Each machine must have a unique IP address to identify itself, so you can contact it directly. '2) Traffic' IP addresses - these are the addresses of your load balancers that the outside world will see and know about. You need at least two of these (so the balancers can have an address each). Unlike the 'front-end' IP addresses, traffic IP addresses are not tied to one machine - they get shared around and moved. For instance, if one of the balancer machines dies, then the other balancer will take its traffic IP address. This way, visitors will always be able to reach your site. '3) Back-end' IP addresses - the balancer machines use these IP addresses to contact the back-end servers. The balancer

As the popularity of the Internet grew, businesses turned to it as a means of extending their own networks. First came intranets, which are password-protected sites designed for use only by company employees. Now, many companies are creating their own VPN (virtual private network) to accommodate the needs of remote employees and distant offices. A typical VPN might have a main LAN at the corporate headquarters of a company, other LANs at remote offices or facilities and individual users connecting from out in the field. http://computer.howstuffworks.com/vpn2.htm Basically, a VPN is a private network that uses a public network (usually the Internet) to connect remote sites or users together. Instead of using a dedicated, real-world connection such as leased line, a VPN uses "virtual" connections routed through the Internet from the company's private network to the remote site or employee. In this article, you will gain a fundamental understanding of VPNs, and

Domain Names Because most people have trouble remembering the strings of numbers that make up IP addresses, and because IP addresses sometimes need to change, all servers on the Internet also have human-readable names, called domain names. For example, www.howstuffworks.com is a permanent, human-readable name. It is easier for most of us to remember www.howstuffworks.com than it is to remember 209.116.69.66. The name www.howstuffworks.com actually has three parts: 1. The host name ("www") 2. The domain name ("howstuffworks") 3. The top-level domain name ("com") Domain names within the ".com" domain are managed by the registrar called VeriSign. VeriSign also manages ".net" domain names. Other registrars (like RegistryPro, NeuLevel and Public Interest Registry) manage the other domains (like .pro, .biz and .org). VeriSign creates the top-level domain names and guarantees that all names within a top-level domain are unique. VeriSign also m

The Internet Client Servers IP Addresses To keep all of these machines straight, each machine on the Internet is assigned a unique address called an IP address. IP stands for Internet protocol, and these addresses are 32-bit numbers, normally expressed as four "octets" in a "dotted decimal number." A typical IP address looks like this: 216.27.61.137 The four numbers in an IP address are called octets because they can have values between 0 and 255, which is 28 possibilities per octet. Every machine on the Internet has a unique IP address. A server has a static IP address that does not change very often. A home machine that is dialing up through a modem often has an IP address that is assigned by the ISP when the machine dials in. That IP address is unique for that session -- it may be different the next time the machine dials in. This way, an ISP only needs one IP address for each modem it supports, rather than for each customer. If you are working on a Windows machi