Wednesday 28 December 2011 at 12:49 pm
ERP or Enterprise Resource Planning also entails the normal accounting operations required in a small and medium sized business, the integration between the post mortem analysis functions, planning procedures and the basic data collection and organizational functions required for a backbone business information system leave business planners wanting an integrated package of data processing functions to interface with the planning procedures.
Linux based open source software packages offer the richest and most rapidly evolving applications. That Redmond Washington vendor can enter a market and abandon it in a matter of a few years, leaving users with unsupported application software. While the life cycle for a release of a desktop operating system may be less than five years, many ERP implementation last two decades or more. Elements of major million dollar ERP software packages contain business logic with roots in the Fortran and Cobol of the 1960's.
Certain SQL based packages lack much business logic entirely and the relatively new, but robust procedural languauge of the Oracle flavor, Plsql is developing and creating an inventory of business logic. But licensing costs drive infoimration system specialists to continue to use applications based on the Unix operating system and the known source code model. These models rely on vendors like Redhat and Novell to maintain expertise at a lower cost while providing the option to 'go it alone' that indeed major banks and telecoms excercise.
Linux, Apache, MySql and Php combine to provide applications for the business community, and with the use of Perl banking providors like Paypal provide incredibly robust and yet secure micro application environments that employ technology in innovative and profitable ways. But businesses that merely outgrow the Quickbooks model, which lacks the aforementioned integration desires that forward thinking business owners seek leave small manufacturers for example to look at packages of the next tier such as Peachtree, MAS-90 and even the Redmond solutions.
However, businesses might come accross three very innovative vendors that use Linux as a basis, yet provide compatibility with Windows and Macinstosh for the most part. Linux in the previously mentioned telecom operations provides the least downtime, and many times Oracle has used Linux to set world records in the database transaction processing arena. For more information on visit www.mansup.net for more information on open source modeled and Linux based LAMP ERP solutions.
Saturday 10 December 2011 at 08:03 am
Conventions for this help guide are required, first, a character struck while holding down the control key are preceded by the CTL- and an enter key (or sometimes it used to be a return key or 'carriage return') is designate with <cr>.
First, what have we gotten into here? Emacs is a full screen character editor that allows arrow keys, which may be much more intuitive to the unfortunate folk that started life on Windows or Macintosh. While everybody knows that 'vi' is the ultimate editor, alas, Emacs is a good idea to learn.
I have gotten into emacs on a file, and am afraid of making modifications, exit without saving;
CTL-X CTL-C
Unfortunately, we can get caught in a situation where Emacs believes that there are changes to be saved, so try this;
CTL-X CTL-C n<cr> yes<cr>
At any rate, if you have issued the CTL-X CTL-C from a neutral start, meaning the context is not determined by Emacs to be something other than exit, you should be getting instructions at the bottom of the screen.
Saving the file
CTL-X CTL-S
Tuesday 06 December 2011 at 1:35 pm
Network operating systems have a wide variety of shapes and sizes, because each organization that employs them has different needs. Some operating systems behave excellently on small networks, and others specialize in connecting many smaller networks rather broad areas. The services performed NOS are: Support for files: that is, create, share, store and retrieve files, essential activities that specializes NOS providing a quick and secure.
Communications: This refers to everything that is sent through the cable. Communication takes place when, for example, someone enters a network, copying a file, email, or print. Services support team: This includes all special services like printing, tape backups, virus scanning on the network, and so on. Back to topics in this section network topology network nodes (computers) need to be connected to communicate. The way in which nodes are connected is called topology. A network has two different topologies: one physical and one logical. The physical topology is the actual physical layout of the network, the way in which the nodes are connected to each other. The logical topology is the method used to communicate with other nodes, the route taken by network data between different nodes of the same. Physical and logical topologies may be identical or different. The most common network topologies are: bus, ring and star. Red bus in a bus topology, each computer is connected to a common segment of the network cable.
The network segment is placed as a linear bus, ie a long cable that goes from one extreme to another network, and which connects each node of the same. The cable can go through the floor, the walls, ceiling, or can be a combination thereof, provided that the cable is a continuous segment. A ring network ring topology consists of multiple nodes together to form a logical circle. Messages are moved from node to node in one direction. Some networks may ring in a two-way messaging, however, are only able to send messages in one direction at a time. The ring topology allows to check if a message is received. In a ring network, the workstation sends a data packet known as arrow or passkey. Red Star One of the oldest types of network topologies is the star, which uses the same method of sending and receiving messages to a phone system, since all messages in a star topology LAN must pass through a central device called connection wiring hub, which controls the flow of data. Back to topics in this section Network architecture networks are composed of many different components that must work together to create a functional network.The components comprising the hardware portion of the network include network adapter cards, cables, connectors, hubs, and even the computer itself. Network components make them, usually several companies.
Therefore, there must be understanding and communication between the manufacturers in relation to how each component works and interacts with other network components. Fortunately, we have created standards that define how to connect hardware components and network protocol (or rules) to use when establishing network communications. The three most popular standards or architectures are: ARCnet, Ethernet and Token Ring. Ethernet and Token Ring are supported standards organization IEEE (Institute of Electrical and Electronics Engineers), while ARCnet is an industry standard that has recently become one of the standards of ANSI (American National Standards Institute). ARCnet Networks Produced in the seventies by Datapoint Corporation, the network of connected computing resources (ARCnet) is a standard accepted by the industry, but does not carry a standard number of IEEE. ANSI recognized standard ARCnet formal, which made part of the ANSI 878.1 standard LAN. As supports a data transfer speed of 2.5 Mbps, ARCnet uses a bus logical topology and a slight variation of the physical topology of a star. Each network node is connected to a passive or an active hub. The NIC in each computer is connected to a cable which in turn is connected to an active or passive hub. ARCnet is based on a signal path scheme (token passing) to manage the flow of data between network nodes. When a node holds the token (signal), can transmit data over the network. All nodes, except the intended recipient, ignore the data. As it passes the token to each node, the node can send data. Since each node can send data only when it has the token in ARCnet collisions do not happen that often occur in a scheme such as CSMA / CD. Therefore, ARCnet is less susceptible to saturation of the Ethernet network. For a while ARCnet was the most popular LAN standard, but due in part to its relatively low speed (2.5 Mbps compared to 10 Mbps Ethernet), rarely used for new installations. Ethernet Ethernet networks, which is also known as IEEE 802.3, is the most popular standard for LANs that currently use. The 802.3 standard uses a bus logical topology and physical topology of a star or bus. Allows Ethernet data through the network at a speed of 10 Mbps Ethernet uses a data transmission method known as Multiple Access with Carrier Detection and Collision Detection (CSMA / CD). Before a node sends any data via an Ethernet network first listens and realizes if another node is transferring information. Otherwise, the node transfers the information through the network. All other nodes listen to the selected node and receive the information. If two nodes try to send data over the network at the same time, each node will notice the collision and wait a random amount of time before returning to ship.
The logical topology Ethernet bus allows each node takes turns in transmitting information across the network. Thus, the failure of a single node failure does not cause the entire network. Although CSMA / CD is a quick and efficient way to transmit data, a heavily loaded network could reach saturation point. However, with a properly designed network, saturation is rarely worrisome. There are three standard Ethernet, 10BASE5, 10BASE2, and 10BASE-T, which define the type of network cable length specifications and the physical topology to be used to connect nodes in the network. Token Ring Token Ring, also known as IEEE 802.5, was developed by IBM and some other manufacturers. With operation at a speed of 4 Mbps or 16 Mbps Token Ring uses a logical ring topology and a star physical topology. The NIC for each computer connected to a cable which, in turn, plugs into a central hub called a multistation access unit (MAU). Token Ring is based on a signal step scheme (token passing), ie passing a token (or signal) to all computers on the network. The computer is in possession of the token is authorized to transmit information to another computer on the network. When finished, the token is passed to the next computer in the ring. If the next computer has to send information, accepts the token and proceeds to send it. Otherwise, the token is passed to the next computer on the ring and the process continues. The MAU automatically bypasses network node that is not lit. However, since each node in a Token Ring network and then examines each token broadcast (signal), a node can malfunction to stop work across the network. Token Ring tends to be less efficient than CSMA / CD (Ethernet) networks with low activity, it requires additional overhead. However, with increasing network activity, Token Ring becomes more efficient than CSMA / CD. Several new technologies new technologies that meet the needs of today's networks, including Fast Ethernet, FDDI, Frame Relay and ATM. Fast Ethernet, also called 100BASEX, is an extension of the Ethernet standard that operates at speeds of 100 Mbps, up to 10 times greater than the standard 10 Mbps Ethernet interface for data distribution optical fiber (FDDI) is a standard for data transfer by fiber optic cable.
The ANSI standard for FDDI X3T9.5 specifies a rate of 100 Mbps Since the fiber optic cable is not susceptible to electrical interference or as susceptible to the degradation of the network signal as with standard network cable, FDDI allows the use of much longer cable than other network standards. The Frame Relay (Frame Relay) is a connection-oriented service to move data from one node to another at a reasonable speed and low cost. The frame relay can be seen as a virtual leased line. The user rents a permanent virtual circuit between two points and then you can send frames or frames (ie, packages) up to 1600 bytes between them. Besides competing with leased lines, frame relay competes with X.25 permanent virtual circuits. ATM means Asynchronous Transfer Mode, is a set of international standards for data transfer, voice and video through a network at very high speeds. Since it operates at speeds ranging from 1.5 Mbps to 1.5 Gbps, ATM incorporates standards of Ethernet, Token Ring and FDDI for data transfer. Back to topics in this section Description of the OSI model The OSI reference model is the current network architecture more prominent. The aim of this is to develop standards for open systems interconnection (Open System Interconnection, OSI). The term OSI is the name given to a set of standards for communication between computers, terminals and networks. OSI 7-layer model, where each layer defines the procedures and rules (standard protocols) that communications subsystems must follow in order to communicate with their corresponding processes of the other systems.
This allows a process running on a computer, can communicate with a similar process on another computer, if they implement the same communication protocols OSI layers. Some of the functions of each layer or level are described below: Level of Implementation. It defines a number of applications for communication between different systems, which manage: File Transfer (FTP). Exchange of messages (email). Presentation level. This layer performs the following functions: It formats the information to view or print. Interpreting the codes that are in the data (code conversion). It manages data encryption. It performs the data compression. Level of Session. Provides mechanisms for organizing and structuring dialogues between application processes. It acts as a moderating element can coordinate and control the exchange of data.
Tuesday 06 December 2011 at 1:10 pm
To minimize collisions network adminstrators segment the network into various pieces which only affect collisions within each segment, not the entire network.
With layer-2 switching devices, switches and bridges, layer-2 devices, can be used to split a big network into two separate collision domains. A broadcast domain works at layer 3 of the OSI model with routers. A packet sent to a network's broadcast address will resonate throughout a broadcast domain.
ARP and RARP ARP (Address Resolution Protocol) turns an IP (network) address into a hardware address (MAC address). It finds the hardware address of a computer with the given IP address.
RARP (Reverse Address Resolution Protocol) does the opposite, i.e. turn a MAC address into an IP address. Remember that. ARP works by flooding the network with a broadcast saying "What is the MAC address for this IP address?" The entire network hears the question, but only the computer with that IP address is supposed to respond.
WAN technologies - PPP, frame relay, and ISDN.
PPP (Point-to-Point Protocol) is the protocol you use to connect to your ISP over a phone line, consisting of two protocols: LCP (Link Control Protocol), and NCP (Network Control Protocol). LCP is responsible for establishing and configuring the point-to-point connection. NCP is really just an abstraction of several protocols to let PPP work with things like IP.
ISDN (Integrated Services Digital Network) was the primary form of direct digital telphony interface, before DSL, T1 and cable offered far greater bandwidths.
Frame relay uses FECN (Forward-Explicit Congestion Notification) and BECN (Backward-Explicit Congestion Notification) to let other systems on the network know of congestion. FECN is used to let systems ahead of you know that the network is congested and to expect slower transmissions from you; BECN is used to advise systems transmitting to you that the network is congested. BECN is a request for the sending system to slow down (similar to a "source quench" message). Frame relay also uses something called DE (Discard Eligibility) to help control congestion. DE actually uses one bit of each frame on the network to indicate whether DE is on or off; If DE is turned on for a frame, that frame is considered disposable. When a switch on a frame relay network gets congested, frames with the DE bit turned on will be thrown away to conserve bandwidth.
Non-OSI network models - The 7-layer model is the industry standard for abstraction of a network component's function, however, there are two other standards involved in Cisco certification, the Cisco hierarchical model and The DoD model.
Cisco's networking model has 3 layers: Core, Distribution, and Access. The Core layer is the very core or backbone of the network. The Core layer's routers must be fast and have high-bandwidth connections. The Access layer is the point where people actually use the network; The workstations that users use are in the Access layer, as well as local workgroup's switches or hubs. The Distribution layer is a concept midway between the Core and the Access layers. Cisco explicitly defnes this model to stress that breaking up collision domains should ONLY be done at the Access layer. Cisco gets very excited about this topic.
The U.S. Department of Defense (DoD), the folks who originally created TCP, also created a four-layer network model which basically combines several of the OSI model layers into single layers: The bottom layer of the DoD model is the Network Access layer. It coextends with the Physical and Data-Link layers of the OSI model. The second layer of the DoD model is the Internet layer. It corresponds to the Network layer of the OSI model. The third layer of the DoD model is the Host-to-Host layer. It corresponds to the Transport layer of the OSI model. The top layer of the DoD model is the Process/Application layer. It coextends with the Session, Presentation, and Application layers of the OSI model.
Virtual LANs (VLANs) A virtual LAN (VLAN) is one of those concepts which is not usually very well explained, but is actually pretty simple once you can grasp the concepts behind it. To make an analogy, if you're familiar with PC support, you're probably aware of hard disk partitioning and how it works; You can have one single physical hard disk drive in a computer, but it can be divided into separate partitions, each of which is treated as a separate "logical" or "virtual" disk drive. Even though they all exist on the same physical device, they are treated as separate entities. A VLAN works much the same way.
It is network segmentation achieved through a single switch. You configure the switch so that some computers are connected to each other, and others are not. The result is that each connected community of computers becomes a virtual LAN, seeming to exist separately, even though they all really run through the same physical switch. VLANs create a small problem by separating computers that sometimes need to talk to each other. Virtual LANs are mainly organizational in their intent; They do not actually achieve anything useful other than making things a little more nicely logical and organized on the network. Creating a VLAN is easy; Just use the vlan command from global configuration mode. The syntax is as follows: vlan # name [name] ...Where # is the number of the VLAN, and [name] is the actual name you want to give it. For example, to create VLAN number 4 and name it "Accounting" to mark it as belonging to the accounting department, you'd type: vlan 4 name Accounting Cisco networking equipment uses VTP (Virtual Trunking Protocol) to keep on top of what VLANs exist. VTP is like RIP for VLANs; It propagates VLAN information throughout the entire network, so you don't have to. VTP has three modes of operation: Server, Client, and Transparent.
Monday 05 December 2011 at 11:51 am
When Windows 2000 came out, it was expected to be one of the biggest disasters in the history of the computer industry. While W2K was bad, it was marketed by Microsoft as an OS for business users rather than for home users (as Windows NT always was), so ultimately, it didn't affect too many people except the corporate folks who, by that time, had probably already become well accustomed to the lunacy that is NT-based Windows. But Windows XP is marketed as the Windows for general users, and since its release, XP has become the most widespread and damaging computer virus our world has ever seen. Windows XP is perhaps the ultimate meme virus--a virus which spreads by thought and culture rather than by biological or technical exploitation. There is no single event that has ever occurred which has negatively impacted the face of computing so much as the release of Windows XP. This page endeavors to explain why. Windows Product Activation I shouldn't really need to say any more about this; It's self-explanatory. However, given how many people use Windows XP, apparently it's not self-explanatory enough, so I feel the need to elaborate on this somewhat. When you install Windows XP, a little notice keeps popping up saying "x days left for activation", where x is of course how many days remain before Windows XP will stop working. (You have 30 days from the time you install it.) That Windows XP is deliberately configured to be a ticking time bomb is reason enough not to use it.
The fact that you need to register information about your computer to use Windows XP means that I will never, ever install XP on any computer that I own, except for experimental or testing purposes, in which case I will not "activate" it. What's amazing about WPA is how Microsoft receives praise from people by being so generous as to give you 30 days to activate your OS. This is akin to the generosity exhibited by organized crime groups which are generous enough to provide you 30 days to cave in to their demands before they slaughter your entire family. UPDATE: The situation was made even worse by the February 2005 revelation that Microsoft was going to disable Internet activation for OEM versions of Windows XP. Microsoft claimed that this was to subvert piracy: "To reduce the illegal trafficking of these OEM product keys". Let's get a few facts straight, for those who aren't sure what this means. First of all, an "OEM version of Windows XP" means a version of XP that comes preinstalled on a fully-configured computer from an OEM, a company that has its own brand on its PCs, like Dell, Compaq, HP, etc. This is as opposed to a non-OEM version of Windows XP, which would be one that you buy off the shelf as a separate software product, rather than pre-installed on a new computer. This announcement will not apply to non-OEM versions of Windows XP (at least not yet, although Microsoft may decide to change that). It will only apply to people who are re-installing Windows XP on their OEM computers. The computers will ship with Windows XP pre-activated, but if you ever want to reinstall XP (which some people do frequently because it's often easier than troubleshooting problems), this announcement will apply. So how else can you activate Windows XP? Believe it or not, the only other way is by telephone.
You actually need to call a Microsoft telephone number and speak to a customer service rep, who will ask you questions about your copy of Windows XP to determine if it's a legal copy. Stop and read that sentence again if the magnitude of it didn't strike you the first time: Microsoft has adopted apolicy of interrogating its customers to ensure that they in fact bought their copies of Windows XP. It just keeps getting worse. What's amazing is that people still blindly follow what Microsoft tells them to do. They're actually going to call Microsoft on the telephone and wait to speak to a service rep! I can't even imagine what this means for the many people (like me) who don't have telephone service because they don't want or need a phone in their house. As sad and damaging as WPA has been, however, in a way it's actually been a good thing for the world, because it's served to limit the spread of Windows. People have discovered that Windows XP simply cannot be used on installations in remote places which have no Internet access and no telephones, such as virtually any computer running in an area that's not municipally zoned. These people, forced to seek other alternatives, have finally discovered non-Windows operating systems and broken the long chain of Windows dependency. Unfortunately this hasn't happened much since most computers now have Internet connections, but it's a start. Now if Microsoft would just start charging several million dollars per Windows license, we could finally divert the world from yet another lemming march and get back to some serious stuff. Windows XP is not real Non-NT-based versions of Windows can be booted in real mode, which is the opposite of what Windows used to call 386 enhanced mode. In real mode, programs actually run in your computer's real memory space, instead of having virtual memory spaces (or "virtual machines" as Java programmers like to call them) allocated for them. While virtual mode, protected mode, or whatever you want to call it is useful for everyday multitasking, it's simply absurd to create a commercial operating system that doesn't allow software to directly interface with hardware. Try changing your interrupt vectors or PIT timing in Windows XP. Simple tasks like these, which could be easily done in real mode, become impossible with Windows XP. Of course, this is all in keeping with the computer industry's laws of economics.
If you can't actually use the standard PC functions which have been built into the hardware of every PC made since the original IBM PC came out in 1984, then you must play by Windows XP's rules, writing all your hardware drivers and functions to work with XP, since they won't actually work with the computer itself. Why adhere to standards when you can make your own? That's the question Microsoft has long known the answer to: They don't. Side note: Windows XP was not actually the first home edition of Windows to not support booting in real mode; The first was Windows Me (Millennium Edition). However, Windows Me was so widely disliked that nobody took it seriously. (It was essentially Windows 98 with a "System Restore" function, newer versions of Windows Media Player and Internet Explorer, a somewhat revamped GUI, and lacking support for real mode.) Windows XP is genuinely regarded as an actual operating system by many people, which is a frightening lapse of human reason. Services-based architecture This is probably the single worst thing about both Windows 2000 and Windows XP. Let's get one thing settled right now: When you're evaluating the security of any computer today, one of the very first things (if not *the* first thing) you check is what TCP ports are open. It doesn't matter if the computer is a server, a workstation, a home computer, or a forgotten system that's only used for printing labels or something like that; open ports create risk. A system that's actively listening for incoming connections and which intends to respond to attempted connections is something you don't want on your network unless you really have to be listening on those ports. Let's make another thing clear: Windows 98 allows you to not only boot Windows, but even connect to the Internet, without having any open ports. Not one. If you're on a computer with Windows 98 and you're connected to the Internet, but not running any Internet processes or servers, you can open a command prompt and type netstat -a to discover that absolutely nothing shows up. Nothing. No connections, no listening ports.
If something *does* show up, it either means that some connections are still waiting to close (this would be the case if anything has a status of "CLOSE_WAIT"), you have some active connections ("ESTABLISHED"), or some program is acting as a server ("LISTENING"). But the point is that if no programs are doing anything, Windows 98 won't have a single port operating. That's good. It means that any incoming TCP connections will be turned away simply because they have nowhere to connect to. It doesn't necessarily make the computer secure, but it's a good start. Windows 2000 and Windows XP both pretty much require you to run a service called Remote Procedure Call (RPC). RPC is the service that's legendary for being full of holes. It was RPC that ended up being entirely responsible for the infamous Blaster worm that infected countless Windows installations in 2003. RPC is a service, meaning by its very nature, it sits in the computer and listens for other machines that want to connect to it. While this doesn't automatically mean a computer is vulnerable (in fact, to be fair, it wasn't RPC itself that made Blaster possible, but rather the implementation of RPC that Microsoft used in Windows), there's really no reason to be listening for connections this way unless you need to. By any standard, you shouldn't have to be running RPC as a service to use your computer. Windows 98 certainly didn't require it. The basic rule of thumb among almost any security-conscious system admin is: If you're not using a service, turn it off.
You'll save system resources and close a potential entry point. Here's the catch: In Windows 2000/XP, turning off RPC is like turning off your entire computer. One of the biggest reasons why NT-based versions of Windows are so prone to security holes is that instead of actually using normal computer functions, which is what an operating system is supposed to do, Windows 2000, XP, and their ilk think that it's a better idea to set up a server on a computer so that it can essentially use TCP/IP (networking protocols intended for use in transmitting messages to other computers) to send messages to itself. Forget networking with other computers, if you use Windows 2000/XP and turn off RPC, you won't even be able to use your OWN computer. Applications that use the MMC (Microsoft Management Console) won't work, for example, which is particularly hilarious when you consider that the Services control panel used to turn off RPC is itself a MMC window, meaning that if you turn off RPC, you're essentially heading down a one-way street, because you won't be able to use the Services control panel to turn it back on again. Microsoft apparently tries to prevent you from doing this by disabling the "Stop" option for the RPC service, but you can still change the service's status to "Disabled", and if you do this and then reboot, say hello to a crippled Windows installation. (Quick tip if this happens to you: You can turn RPC back on by running Regedit, and checking the HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\RpcSs\Start value. It should be set to 4, which is the code for "Disabled"; if you set it back to 2, which means "Automatic" (i.e. it starts automatically when the computer boots) and then reboot, RPC should start working again.) Try running netstat -a on Windows 2000 or XP. You're almost guaranteed to see several ports listening that shouldn't be. You can probably close some of them, but not all of them, because some of them are needed by Windows. Then try running the Services console and seeing how many "services" Windows has running in the background; a typical Windows 2000/XP install has around 20 running by default! Some of these services can't be stopped because Windows itself depends on them, while others serve important functions that will cripple important parts of your computer's functionality if you disable them. Annoyingly, Windows seems to lump both network services (i.e. programs that actually listen for incoming network connections) and background processes (which, at least in the Unix/Linux world and in general parlance, are properly called "daemons") under the same "Services" umbrella, meaning it can be tough to tell the services that don't create risk from the ones which do. Either way, however, it is utterly foolish that any operating system would base its functionality on running a server just so that it can send messages to itself. Any OS that does this basically ties your hands behind your back, because it creates holes that you just can't plug.
Any OS that does this is an OS that should not be used, except maybe as a joke. Windows XP is a lightning rod for security attacks A majority of the viruses/adware/spyware/exploits that propagate on the Internet are designed to target Windows XP. This is logical, given that XP is the most commonly-used OS on computers today, but it's also a good reason not to use XP. On my Windows computers (those which don't run on some variant of BSD or Linux), I still exclusively use Windows 98. You may think it's funny that I'm using an OS that's almost 10 years old, but the reason is simple: Windows 98 does everything an operating system needs to do, and it's actually immune to many of the common attacks that make their rounds on the Internet. An example is the aforementioned Blaster worm, which spreads via an exploit in the RPC service that's used in Windows 2000/XP. Now, while you could protect yourself from Blaster by patching the service it uses, there's a much simpler way to protect yourself: Never install an operating system that uses that service in the first place! I was running several Windows 98-based computers when Blaster spread like wildfire across the Internet, and I never even paid it a moment's notice, simply because my operating system didn't even *HAVE* the RPC service that Blaster exploits. The worm just bounced off my computers harmlessly. It's like the difference between finding a cure for cancer and going back in time to prevent cancer from having ever existed in the first place. One works, but the other is better. This is not necessarily a defense of "security through obscurity". It is simply the basic observation that since script kids tend to target the most popular software in use, you can avoid some problems by using less popular software. Incidentally, this applies equally to other software, including web browsers, e-mail clients, etc. This is not to say that any software is 100% secure, because none is, but some programs are more secure than others, and this isn't always for technical reasons; sometimes it's simply for sociological reasons.
Monday 05 December 2011 at 11:41 am
EMACS keystrokes
EMACS is a Unix/Linux text editor which lots of people like because it can do a lot of stuff. EMACS has many keystroke controls, but the only two which you really need to know in order to use it are as follows: Save document: C-x, C-s Exit EMACS: C-x, C-c (C-x is EMACS shorthand for CTRL-x. It uses so many CTRL-key combinations that it's more practical to shorten it that way. Incidentally, for ALT-key combinations, EMACS uses M instead of A as you might expect; For example, M-x means press ALT-x. This stands for "meta".)
Another neat keystroke to remember is M-x. (Yes, that's ALT-X.) This lets you run commands in EMACS by name; Every command in EMACS has a name, but the most commonly-used ones are bound to specific keystrokes so they can be run quickly. If a command is not bound to a keystroke, you can run it just by pressing M-x and then typing the command name. Press M-x and type doctor at the prompt to run EMACS' "doctor" module, which is the famous ELIZA-like psychiatrist built into it. If this doesn't convert someone from using pico, nothing will.
Also note that EMACS notation uses "RET" to refer to the ENTER key. This derives from the days when the alphanumeric ENTER key was often labeled "RETURN", because it was analogous to a typewriter carriage return. vi commands vi (short for "visual") is the most popular text editor in Unix/Linux. It's not as feature-and-keystroke laden as EMACS, but that's why most people like it.
vi - press ESC and then type a colon to get to the vi command prompt. Once there, the following commands apply: w Save file q Exit vi wq Save file AND exit vi, all in one handy command. Environment variables in bash - The most important are PATH and PS1. PATH is the set of directories the shell will look in for the program to run when you type a command (it works exactly like DOS' PATH variable). PS1 is what your Linux command prompt looks like (it works exactly like DOS' PROMPT variable). Linux hotkeys CTRL-Z forces an exit to most programs and returns you to your shell (where you can then use kill (or kill -9 ;) ) to get rid of the process. CTRL-ALT-F1 through CTRL-ALT-F6 switch between virtual consoles.
Special characters at the command prompt *nix systems have a number of "special" characters which let you do some fancier tricks at the command line. Here are a few: ` This is a grave accent, NOT an apostrophe. The grave accent is the "backwards apostrophe", located under the tilde key (right next to the key for the number 1 near the top of the keyboard). It lets you execute a command within a command. Use two grave accents to enclose a command, and the result of that command will be used. If that didn't come through too clearly, here's an example: echo `cat /home/foo` Typing this will output the contents of /home/foo.
This is because cat listed the file, and then the results of that (the contents of the file) were used on the command line for echo. This is a simple example, but obviously more complicated (and useful) things can be done with this. & This symbol is used at the end of a command. It executes the command and then returns to the command prompt without waiting for the command to finish. It's useful for Xwindows programs, when the program runs in a window and then prevents you from accessing the console window you used to run it until you close the program. For example, typing this: xeyes& ...would run xeyes and still let you use the console window you were on without having to close xeyes first. ~ This symbol (the tilde) lets you specify a user's home directory. For example, ~foobar specifies the home directory for the user named foobar. And typing cd ~foobar would change to that user's home directory.
Note that you can also use just a tilde without a username to specify your own home directory. ! The exclamation mark is interpreted as a history reference. Don't ask me what that means, but basically, you can't use an exclamation mark by itself at the command line. If you want to use one, precede it with a backslash so the computer will realize you actually want to type an exclamation mark and not a history reference. So, type \! instead of just ! . Windows is a trademark of Microsoft Corp., so don't pretend you thought of it yourself. Back to the main page This page hosted by Get your own Free Homepage
Saturday 03 December 2011 at 06:05 am
Perl is sometimes called the Swiss-Army Chainsaw of programming languages.
Perl is an interpretive language which can easily be run on Linux and Windows platforms. With strong string handling, file i/o and the fame of the term 'Perl Regular Expressions', Perl has brought an rich and well defined lexicon to the world of procedural definition.
Why Procedural?
Unlike a GUI, a procedure is concise and well defined. While proprietary computing purveyors like Microsoft seek to hide the inner workings of their systems, the fact is we all know that there is a registry. They try to hide the fact that the computer code is text, but they can't entirely.
Perl gets right to the issue, doesn't hide, and short little programs can be quite powerful
Perl and the World Wide Web
Perl became widely used with the CGI server structure with Apache and the world wide web. Scripts in Perl are virtually unhackable in the CGI directory of a website making it an ideal method of managing login methods and secure server functions.
Syntax
Perl's syntax builds on several Linux and Unix boilerplate functions awk, sed, shell and C. Perl also often has many ways to achieve a task, and the resulting code is sometimes compared to APL. Some say that no Perl programmer can read anyone elses code. Nonetheless, skilled perl programmers produce powerful reults and the interpretaive nature allows quick development.
Perl Concatenation
Like PHP, Perl uses the period as the concatenation character.
Weak typing.
While Perl is a powerful text manipulation language, it is not a fast math language, and was not envisioned for heavy math operations. Perl also can perform quickly boolean operations on bytes like && for AND and || for OR.
Hello World with Perl
On your Linux system with Perl, create this program and chmod it to 755.
#!/usr/bin/perl -w
print "Hello World";
If you don't like the lack of a newline, add \n to the end of the output string. This assumes that your Linux system interprets Perl with /usr/bin/perl, this may vary.
Thursday 01 December 2011 at 2:59 pm
Windows 7 IE crashes with GEforce graphics completely eliminated by using 64 bit version of IE, Start -> All Programs -> Internet Explorer (64 bit)
NVIDIA GeForce 210 Driver Version 8.17.12.8562
