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• Multiple computers on Ubuntu One

  - by L R Bellmore Jr

  I have added files from 4 computers to Ubuntu One. One computer failed. What happens to the files that I uploaded. Are they still on Ubuntu One? How come when I upload a file from computer A, computer B with the same Ubuntu One account does not sync and load that file into computer B - That has created this question.. what happens to files from computers from which I uploaded documents when those computers are no longer active or failed, or no longer have Ubuntu One on that computer from which the files were uploaded... Have I lost the files? The followup question is how come files from Computer A uploaded to Ubuntu One don't sync to Computer B. That is a related question. I need to shut down a computer, reformat the hard drive and install Linux on the entire harddrive instead of a dual boot with Windows XP as I am going to use Virtual Machines instead.. what happens to the files from the Windows Dual Boot that were uploaded to Ubuntu One? Are they removed from Ubuntu One and then have I lost those files if I don't backup to another service first.

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• Can I use Ubuntu One to sync data fiies between two remote computers

  - by Sleepy John

  I've got two computers, both running Ubuntu with files in their home folders sync'd in to Ubuntu One. I'd like to know if it's possible to make Ubuntu One automatically download data changes that have been uploaded automatically to Ubuntu One from one computer to the equivalent data file in the other. Clarifying a bit further, I've installed Red Notebook in both computers and so they each have their own /.rednotebook/data folder containing a series of .txt files corresponding to the monthly entries in each of them. These are sync'd to upload any changes to those .txt files to Ubuntu One. My question is can I, and if so how, do I make Ubuntu One automatically download and replace those .txt files in the other computer after they've been updated and uploaded from the first computer? I did labouriously manage to download all those text files which had been uploaded from the first computer, from Ubuntu One one-by-one to the second computer, but what I want to do is automate this process and that's where I'm stuck. I'm aware that things could get a bit complicated if both my computers were on-line at the same time and both were simultaneously making different Red Notebook entries, so that's not the scenario I'm trying to cover. All I want to achieve is that whatever updates to the files have been uploaded by one computer, will automatically be downloaded to the same-named files in the other computer as soon as that second computer appears on line and detects that Ubuntu One has matching but more recent sync'd files than the ones it's holding.

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• RDMA architecture - do you need adapters on both ends?

  - by Bobb

  I know Linux can use RDMA NICs like Solarflare... I just found Intel has something like that NetEffect cards. But Intel is talking all about clusters.. Can someone please explain. If I want low-latency networking and install RDMA NIC on my server. Is there limitation on where the cable can go? Is there a specific device expected on the other end? Is it special RDMA switch or RDMA adapter before switch or what? Why is this cluster talk? What if I want a single server with Windows (I can install HPC Windows or Windows 2008 R2)?

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• rsync not copying hard links

  - by A.Ellett

  I have two computers (both MacBook Airs) for which I sync one directory tree in both, but not the entire hard drive or any other directories. Let's say on computer A the directory is /Users/aellett/projects Let's say on computer B the directory is /Users/bellett/projects Generally, I'll log into computer B and then remotely connect to computer A as user 'aellett'. As super user I sync the two project directories as follows: rsync -av /Volumes/aellett/projects/ /Users/bellett/projects/ and this works as expected. On both computers I have another file letter.txt in a different directory which is not getting synced. Let's say on computer A the file is found in /Users/aellett/letters On computer B the file is found in /Users/bellett/correspondence Generally, I don't want to share what's not included in /Users/<username>/projects. But I do want to share this particular file. So on both computer I made a correspondence directory in projects. And then I made hard links as follows On computer A: ln /Users/aellett/letters/letter.txt /Users/aellett/projects/correspondence/letter.txt On computer B: ln /Users/bellett/correspondence/letter.txt /Users/aellett/projects/correspondence/letter.txt The next time I synced the two computers I did the following rsync -av -H /Volumes/aellett/projects/ /Users/bellett/projects/ When I checked on computer B, /Users/bellett/projects/correspondence/letter.txt was correctly synced. But, the hardlink to /Users/bellett/correspondence/letter.txt was no longer there. In other words, /Users/bellett/projects/correspondence/letter.txt was identical to /Users/aellett/projects/correspondence/letter.txt but it differed from /Users/bellett/correspondence/letter.txt. Since these two files were hard linked on both computers, I expected them to still have the hard link. Why are my hard links not being preserved?

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• Computer: Tea. Earl Gray. Hot.

  - by Randolpho St. John

  I just bought an awesome geek mug and thought I'd share:   You can get it too, if you head over to Cafe Press.

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• Oracle Unified Method (OUM) Release 5.6

  - by user714714

  ORACLE® UNIFIED METHOD RELEASE 5.6 Oracle’s Full Lifecycle Methodfor Deploying Oracle-Based Business Solutions About | Release | Access | Previous Announcements About Oracle is evolving the Oracle® Unified Method (OUM) to achieve the vision of supporting the entire Enterprise IT Lifecycle, including support for the successful implementation of every Oracle product. OUM replaces Legacy Methods, such as AIM Advantage, AIM for Business Flows, EMM Advantage, PeopleSoft's Compass, and Siebel's Results Roadmap. OUM provides an implementation approach that is rapid, broadly adaptive, and business-focused. OUM includes a comprehensive project and program management framework and materials to support Oracle's growing focus on enterprise-level IT strategy, architecture, and governance. Release OUM release 5.6 provides support for Application Implementation, Cloud Application Implementation, and Software Upgrade projects as well as the complete range of technology projects including Business Intelligence (BI) and Enterprise Performance Management (EPM), Enterprise Security, WebCenter, Service-Oriented Architecture (SOA), Application Integration Architecture (AIA), Business Process Management (BPM), Enterprise Integration, and Custom Software. Detailed techniques and tool guidance are provided, including a supplemental guide related to Oracle Tutor and UPK. This release features: Business Process Management (BPM) Project Engineering Supplemental Guide Cloud Roadmap View and Supplemental Guide Enterprise Security View and Supplemental Guide Service-Oriented Architecture (SOA) Governance Implementation Supplemental Guide "Tailoring OUM for Your Project" White Paper OUM Microsoft Project Workplan Template and User's Guide Mappings: OUM to J.D. Edwards OneMethodology, OUM Roles to Task Techniques: Determining Number of Iterations, Managing an OUM Project using Scrum Templates: Scrum Workplan (WM.010), Siebel CRM Enhanced / Updated: Manage Focus Area reorganized by Activities for all Views Oracle Architecture Development Process (OADP) View updated for OADP v3.0 Oracle Support Services Supplemental Guide expanded to include guidance related to IT Change Management Oracle User Productivity Kit Professional (UPK Pro) and Tutor Supplemental Guide expanded guidance for UPK Pro Service-Oriented Architecture (SOA) Application Integration Architecture (AIA) Supplemental Guide updated for SOA Tactical Project Delivery View Service-Oriented Architecture (SOA) Tactical Project Delivery View expanded to include additional tasks Siebel CRM Supplemental Guide expanded task guidance and added select Siebel-specific OUM templates WebCenter View and Supplemental Guide updated for WebCenter Portal and Content Management For a comprehensive list of features and enhancements, refer to the "What's New" page of the Method Pack. Upcoming releases will provide expanded support for Oracle's Enterprise Application suites including product-suite specific materials and guidance for tailoring OUM to support various engagement types. Access Oracle Customers Oracle customers may obtain copies of the method for their internal use – including guidelines, templates, and tailored work breakdown structure – by contracting with Oracle for a consulting engagement of two weeks or longer and meeting some additional minimum criteria. Customers, who have a signed consulting contract with Oracle and meet the engagement qualification criteria, are permitted to download the current release of OUM for their perpetual use. They may also obtain subsequent releases published during a renewable, three-year access period. Training courses are also available to these customers. Contact your local Oracle Sales Representative about enrolling in the OUM Customer Program. Oracle PartnerNetwork (OPN) Diamond, Platinum, and Gold Partners OPN Diamond, Platinum, and Gold Partners are able to access the OUM method pack, training courses, and collateral from the OPN Portal at no additional cost: Go to the OPN Portal at partner.oracle.com. Select the "Partners (Login Required)" tab. Login. Select the "Engage with Oracle" tab. From the Engage with Oracle page, locate the "Applications" heading. From the Applications heading, locate and select the "Oracle Unified Method" link. From the Oracle Unified Method Knowledge Zone, select the "Implement" tab. From the Implement tab, select the "Tools and Resources" link. Locate and select the "Oracle Unified Method (OUM)" link. Previous Announcements Oracle Unified Method (OUM) Release 5.6 Oracle Unified Method (OUM) Release 5.5 Oracle Unified Method (OUM) Release 5.4 Oracle EMM Advantage Retired Retirement of Oracle EMM Advantage Planned for December 01, 2011

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• Computer locking up, looking for bootable hardware diagnostic tool.

  - by Carl Menke

  Well today I helped my friend build a computer. All went pretty well until we got to installing Win7. Thing is, we thought, it was crashing constantly. I adjusted pretty much every setting in the BIOS and removed as much hardware as possible to try and prevent a crash. No dice. So far I've tried running an Ubuntu live cd without the harddrive installed. Nope, crashed on boot. And then I just tried Microsoft's ram utility disk and it eventually locked up on that (the ram passed though). So it seems to me like it's either the CPU (AMD PhenomII x3) or the motherboard that could be bad, but I don't know how to test them individually for problems. I thought it could be a overheating issue, but the BIOS reports that the CPU temp is fine idling around 34C. Any advice or diagnostic disk that could help me out? TL;DR: Computer locks up frequently during use (cannot even boot/install an operating system), memory is fine, probably CPU or Mobo, BIOS says CPU temps are fine. What should I try?

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• Do I need a degree in Computer Science to get a junior Programming job?

  - by t84

  Do I need to go to Uni to get a job as a Junior C# coder? I'm 26 and have been working in Games (Production) for 6 years and I am thinking of a change, I've had exposure to VB6, VBA, HTML, CSS, PHP, JavaScript over the past few years and did a web design NCFE at College, but other than that, nothing else! I'm teaching myself C# at the moment with books and I was wondering 'how much' I need to learn and also how I can improve my chances of getting a programming job! Am I a late started to learn coding? (I know many people who started at a very young age!) Thanks for the help :)

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• Can I use my computer as an A2DP receiver?

  - by Pierre-Yves Gillier

  First, the problem: I'm using a Cowon MP3 player as my main music player with basic earplugs. It offers A2DP & I'd like to have my netbook (running UNE 10.04) act as receiver. Some resources on the web about a2dp, but most are out of date: http://fosswire.com/post/2008/10/better-bluetooth-audio/ http://jprvita.wordpress.com/2009/12/15/1-2-3-4-a2dp-stream/ http://dpillay.wordpress.com/2010/09/27/ubuntu-10-04-a2dp-awesome-headset-music/

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• Network bridge does not work on Windows 7

  - by D. Strout

  I am trying to use Windows 7 to bridge my wireless and wired connections together to get wireless on a second Windows XP computer (fresh install). The network bridge is created successfully, but when I connect the cable from the first computer with the bridged connections to the second one with just a wired connection, nothing happens. The second computer doesn't connect, and the first computer shows no sign of anything different. I tried bridging the connections of a third computer, and connecting this computer to the second computer. This worked (third computer bridged the wireless to the second computer). Thus, the problem must be with the first (Win 7) computer. However, I have no idea what the problem could be. All Internet Connection Sharing is turned off. Homegroup is disabled (it was originally enabled, I thought that might be a problem, so I disabled it). Also, I had VMWare fusion installed, and that created extra items in the "This connection uses the following items" box in the properties dialog. Thinking this might be causing issues, I uninstalled that too. Still, with everything I tried, I can't get it to work. Any suggestions? Edit: Another thing I noticed that might be worth mentioning: The network icon in the Win7 taskbar has a red X on it that means it's not connected, but when I click the icon, it says connected next to my wireless connection, and I am able to access the internet.

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• Do I need a degree in Computer Science to get a Jr Programming job in the world? [closed]

  - by t84

  As above really, do I need to go to Uni to get a job as a Junior C# coder? I'm 26 and have been working in Games (Production) for 6 years and I am thinking of a change, I've had exposure to VB6, VBA, HTML, CSS, PHP, JavaScript over the past few years and did a web design NCFE at College, but other than that, nothing else! I'm teaching myself C# at the moment with books and I was wondering 'how much' I need to learn and also how I can improve my chances of getting a programming job! Am I a late started to learn coding? (I know many people who started at a very young age!) Thanks for the help :)

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• Computer Networks UNISA - Chap 14 &ndash; Insuring Integrity &amp; Availability

  - by MarkPearl

  After reading this section you should be able to Identify the characteristics of a network that keep data safe from loss or damage Protect an enterprise-wide network from viruses Explain network and system level fault tolerance techniques Discuss issues related to network backup and recovery strategies Describe the components of a useful disaster recovery plan and the options for disaster contingencies What are integrity and availability? Integrity – the soundness of a networks programs, data, services, devices, and connections Availability – How consistently and reliably a file or system can be accessed by authorized personnel A number of phenomena can compromise both integrity and availability including… security breaches natural disasters malicious intruders power flaws human error users etc Although you cannot predict every type of vulnerability, you can take measures to guard against the most damaging events. The following are some guidelines… Allow only network administrators to create or modify NOS and application system users. Monitor the network for unauthorized access or changes Record authorized system changes in a change management system’ Install redundant components Perform regular health checks on the network Check system performance, error logs, and the system log book regularly Keep backups Implement and enforce security and disaster recovery policies These are just some of the basics… Malware Malware refers to any program or piece of code designed to intrude upon or harm a system or its resources. Types of Malware… Boot sector viruses Macro viruses File infector viruses Worms Trojan Horse Network Viruses Bots Malware characteristics Some common characteristics of Malware include… Encryption Stealth Polymorphism Time dependence Malware Protection There are various tools available to protect you from malware called anti-malware software. These monitor your system for indications that a program is performing potential malware operations. A number of techniques are used to detect malware including… Signature Scanning Integrity Checking Monitoring unexpected file changes or virus like behaviours It is important to decide where anti-malware tools will be installed and find a balance between performance and protection. There are several general purpose malware policies that can be implemented to protect your network including… Every compute in an organization should be equipped with malware detection and cleaning software that regularly runs Users should not be allowed to alter or disable the anti-malware software Users should know what to do in case the anti-malware program detects a malware virus Users should be prohibited from installing any unauthorized software on their systems System wide alerts should be issued to network users notifying them if a serious malware virus has been detected. Fault Tolerance Besides guarding against malware, another key factor in maintaining the availability and integrity of data is fault tolerance. Fault tolerance is the ability for a system to continue performing despite an unexpected hardware or software malfunction. Fault tolerance can be realized in varying degrees, the optimal level of fault tolerance for a system depends on how critical its services and files are to productivity. Generally the more fault tolerant the system, the more expensive it is. The following describe some of the areas that need to be considered for fault tolerance. Environment (Temperature and humidity) Power Topology and Connectivity Servers Storage Power Typical power flaws include Surges – a brief increase in voltage due to lightening strikes, solar flares or some idiot at City Power Noise – Fluctuation in voltage levels caused by other devices on the network or electromagnetic interference Brownout – A sag in voltage for just a moment Blackout – A complete power loss The are various alternate power sources to consider including UPS’s and Generators. UPS’s are found in two categories… Standby UPS – provides continuous power when mains goes down (brief period of switching over) Online UPS – is online all the time and the device receives power from the UPS all the time (the UPS is charged continuously) Servers There are various techniques for fault tolerance with servers. Server mirroring is an option where one device or component duplicates the activities of another. It is generally an expensive process. Clustering is a fault tolerance technique that links multiple servers together to appear as a single server. They share processing and storage responsibilities and if one unit in the cluster goes down, another unit can be brought in to replace it. Storage There are various techniques available including the following… RAID Arrays NAS (Storage (Network Attached Storage) SANs (Storage Area Networks) Data Backup A backup is a copy of data or program files created for archiving or safekeeping. Many different options for backups exist with various media including… These vary in cost and speed. Optical Media Tape Backup External Disk Drives Network Backups Backup Strategy After selecting the appropriate tool for performing your servers backup, devise a backup strategy to guide you through performing reliable backups that provide maximum data protection. Questions that should be answered include… What data must be backed up At what time of day or night will the backups occur How will you verify the accuracy of the backups Where and for how long will backup media be stored Who will take responsibility for ensuring that backups occurred How long will you save backups Where will backup and recovery documentation be stored Different backup methods provide varying levels of certainty and corresponding labour cost. There are also different ways to determine which files should be backed up including… Full backup – all data on all servers is copied to storage media Incremental backup – Only data that has changed since the last full or incremental backup is copied to a storage medium Differential backup – Only data that has changed since the last backup is coped to a storage medium Disaster Recovery Disaster recovery is the process of restoring your critical functionality and data after an enterprise wide outage has occurred. A disaster recovery plan is for extreme scenarios (i.e. fire, line fault, etc). A cold site is a place were the computers, devices, and connectivity necessary to rebuild a network exist but they are not appropriately configured. A warm site is a place where the computers, devices, and connectivity necessary to rebuild a network exists with some appropriately configured devices. A hot site is a place where the computers, devices, and connectivity necessary to rebuild a network exists and all are appropriately configured.

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• Which web server architecture do you think is better?

  - by ngache

  use apache to server dynamic requests that need to be processed by php,and use nginx to serve static files use nginx to serve all requests So the key point is: which of them is more efficient in serving dynamic requests(we have no doubt that nginx is much better than apache in serving static files)?

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• use of CISCO XML gateway Vs BIG IP ASM module as the XML firewall in an architecture

  - by Rajeev

  Hi, I am looking for the advantages and disadvantages of using Cisco XML gateway and BIG IP ASM module in a network.

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• What are some good Software Engineering books for people who didn't formally study Computer Science or Software Engineering?

  - by Kugathasan Abimaran

  I'm a graduate in the electronic & telecommunication field, but working in a software company. I want to continue in this field and going for Masters in it. Can you recommend me some of the best books on software engineering, which cover almost all the topics in software engineering. I am not looking for books about coding practices such as Code Complete, Pragmatic Programmer, but rather general software engineering references.

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• What precautions should I take when moving a hard drive from one computer to another?

  - by Colin Dean

  I'm planning to move a hard drive from one server machine to another. The hard drive is an IDE drive. The motherboards are different, as are the memory and such. In this instance, graphics isn't a problem because this is just Ubuntu Server. Are there any precautions I should take, or steps I can do beforehand, in order to make this go as smoothly as possible? I've of course already backed up /home directories and configurations in /etc and /var.

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• Should I get my masters in Game Design and Development or Computer Science?

  - by Christopher Stephenson

  I am a recent grad with a B.S. in IT while I didn't minor in Game Desgin and development, I took few classes in it. During my job search I have seen that most gaming companies seems to want someone that majored in C.S, mathematics, or physics. During my undergrad I never had to take physics nor did I learn much about data structures and algorithms. These seem to be really important when searching for a job in game development. So I am thinking about going back to school to get my masters in either CS, or GDD. The problem though is which one? I am really not looking to create my own games, I just want to work on games.

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• How could a human factors degree help a computer scientist?

  - by Bob Dole

  I'm wrapping up a masters in CS and already have half the credit hours needed for a degree in Human Factors. I just recently discovered how useful understanding about cognition can help someone that creates user interfaces and am thirsty for more knowledge in the area. For me, it seems that having both a masters in Human Factors and CS would be very marketable but would there be jobs out there that would allow me to apply both? Meaning what I would really like to do is take the requirements for some application, apply different Human Factors theories( GOMS, CE+ ) to developing the interface, maybe do cognitive walk through with users to optimize the UI, then develop the application. Do jobs out there exist like this? The reason I ask, is because I'm wondering if most places just want you to be either a Human Factors Expert or a Developer but not both.

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• Installing nvidia drivers causes computer to boot to command prompt.

  - by levesque

  Hi, I have an Asus u30jc laptop, which comes with the Optimus prime graphics card switching technology that is now supported under 2.6.35, so I decided to give it a try. First I made sure the discrete graphics card was activated and then I installed the drivers proposed by the ubuntu software repository (nvidia-current). However, after rebooting all I got was a command prompt. My graphics card is a nvidia 310M. This is on Ubuntu 10.10 64 bits. What can I do to diagnose/identify the source of this problem? UPDATE: The messsages in my syslog tell me to check the xorg log: Oct 11 12:42:59 u30jc-test gdm-binary[1095]: WARNING: GdmDisplay: display lasted 0.053144 seconds Oct 11 12:42:59 u30jc-test gdm-simple-slave[1450]: WARNING: Unable to load file '/etc/gdm/custom.conf': No such file or directory Oct 11 12:42:59 u30jc-test gdm-binary[1095]: WARNING: GdmDisplay: display lasted 0.038176 seconds Oct 11 12:42:59 u30jc-test gdm-binary[1095]: WARNING: GdmLocalDisplayFactory: maximum number of X display failures reached: check X server log for errors Which I did. I found this message in my /var/log/Xorg.0.log : Fatal server error: [ 113.540] no screens found [ 113.540] What does that mean?

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• How to run a local and external website on same computer with 2 NIC's, 2 Routers and 3 seperate networks?

  - by CandN

  Hello and hopefully I can get some answers to my question, though I think I'm making it more complicated for myself than it has to be. My business is a used auto dealership, and I'm in the process of connecting it to the world - via ethernet from the business server [running Xubuntu] to the ISP's ethernet router/modem, so that I can host our own website (no more than 5-10 people probably visiting at any time - mainly paying their bill), as well as set up a web based internal-intranet site - via DD-WRT Router on the 2nd NIC on the business server - that'll be accessed over Wifi from employees personal devices. On the other end of this is trying to offer free wifi to customers that is completely seperate of the 2 mentioned above networks. Quick Rundown: 1. Web Site for Customers to access. I'm going to use no-ip.org for DNS for the moment being, so I'll have a site that customers can access from anywhere in the world at "mybiz.no-ip.org". This will be forwarded to NIC #1 on the server, possibly at an address like "108.69.." as its being provided an IP from the ISP's modem/router, that is from Time Warner, and they allow NO! configuration options. Web Site for employees to access. I'm trying not to use the server too much as a desktop, only for critical situations, so having a backend thats seperate from the front-facing website is critical. This will be the DD-WRT router hardwired into NIC #2 on the server. This WiFi will be password accessible. Public WiFi for customers. The DD-WRT can seperate networks if I'm correct, I just can't seem to understand how to seperate the 2 and still have internet access on both. I've done it before, but the "Public" wifi (with no password set to connect) kept dropping the connection like a problem was happening that I couldn't figure out. So if I could do a little drawing, this is how it would/should possibly look. ISP -- [Sends Public Facing IP of 108.69.*.1/8] -- ISP Modem Router ISP Modem Router (Ethernet Only) -- [Gives Private IP 108.69.*.2] -- Server NIC #1 Server NIC #1 -- [Gives Private IP 108.69.*.3] -- DD-WRT Router DD-WRT Router -- [DHCP Enabled Giving IP's 172.16.0.0/16] -- Employees Network | | --------- [DHCP Enabled Giving IP's 192.168.1.0/24] -- Public WIFI Hope it's not too confusing, but it anyone could give me some good direct tutorials on how to accomplish this, or if YOU know, then it'll be alot of help. Thanks to all in advance. Need anything else to be explained? Don't hesitate to ask! *Using The LAMP stack with Webmin/VirtualMin -Customer site is located in /var/www2/ -Private Employees site is located in /var/www/ Using no-ip.org's dynamic client updater

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• I'm 15 and I really want to study Computer Science at University, any advice?

  - by Jake

  I already do a lot of programming in my spare time. I'm confident with PHP, Javascript, jQuery which I use in combination with HTML to create mock-up websites. The specific part of programming I want to get in to is web development/web applications. What I'm asking is since I'm pretty sure this is what I want to do, how can I get a head start? Edit: "If you could tell your 15 year-old self to do something that would benefit your programming career, what would it be?" - I just thought of this and thought it would be a better, more specific question :)

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• Computer Networks UNISA - Chap 10 &ndash; In Depth TCP/IP Networking

  - by MarkPearl

  After reading this section you should be able to Understand methods of network design unique to TCP/IP networks, including subnetting, CIDR, and address translation Explain the differences between public and private TCP/IP networks Describe protocols used between mail clients and mail servers, including SMTP, POP3, and IMAP4 Employ multiple TCP/IP utilities for network discovery and troubleshooting Designing TCP/IP-Based Networks The following sections explain how network and host information in an IPv4 address can be manipulated to subdivide networks into smaller segments. Subnetting Subnetting separates a network into multiple logically defined segments, or subnets. Networks are commonly subnetted according to geographic locations, departmental boundaries, or technology types. A network administrator might separate traffic to accomplish the following… Enhance security Improve performance Simplify troubleshooting The challenges of Classful Addressing in IPv4 (No subnetting) The simplest type of IPv4 is known as classful addressing (which was the Class A, Class B & Class C network addresses). Classful addressing has the following limitations. Restriction in the number of usable IPv4 addresses (class C would be limited to 254 addresses) Difficult to separate traffic from various parts of a network Because of the above reasons, subnetting was introduced. IPv4 Subnet Masks Subnetting depends on the use of subnet masks to identify how a network is subdivided. A subnet mask indicates where network information is located in an IPv4 address. The 1 in a subnet mask indicates that corresponding bits in the IPv4 address contain network information (likewise 0 indicates the opposite) Each network class is associated with a default subnet mask… Class A = 255.0.0.0 Class B = 255.255.0.0 Class C = 255.255.255.0 An example of calculating  the network ID for a particular device with a subnet mask is shown below.. IP Address = 199.34.89.127 Subnet Mask = 255.255.255.0 Resultant Network ID = 199.34.89.0 IPv4 Subnetting Techniques Subnetting breaks the rules of classful IPv4 addressing. Read page 490 for a detailed explanation Calculating IPv4 Subnets Read page 491 – 494 for an explanation Important… Subnetting only applies to the devices internal to your network. Everything external looks at the class of the IP address instead of the subnet network ID. This way, traffic directed to your network externally still knows where to go, and once it has entered your internal network it can then be prioritized and segmented. CIDR (classless Interdomain Routing) CIDR is also known as classless routing or supernetting. In CIDR conventional network class distinctions do not exist, a subnet boundary can move to the left, therefore generating more usable IP addresses on your network. A subnet created by moving the subnet boundary to the left is known as a supernet. With CIDR also came new shorthand for denoting the position of subnet boundaries known as CIDR notation or slash notation. CIDR notation takes the form of the network ID followed by a forward slash (/) followed by the number of bits that are used for the extended network prefix. To take advantage of classless routing, your networks routers must be able to interpret IP addresses that don;t adhere to conventional network class parameters. Routers that rely on older routing protocols (i.e. RIP) are not capable of interpreting classless IP addresses. Internet Gateways Gateways are a combination of software and hardware that enable two different network segments to exchange data. A gateway facilitates communication between different networks or subnets. Because on device cannot send data directly to a device on another subnet, a gateway must intercede and hand off the information. Every device on a TCP/IP based network has a default gateway (a gateway that first interprets its outbound requests to other subnets, and then interprets its inbound requests from other subnets). The internet contains a vast number of routers and gateways. If each gateway had to track addressing information for every other gateway on the Internet, it would be overtaxed. Instead, each handles only a relatively small amount of addressing information, which it uses to forward data to another gateway that knows more about the data’s destination. The gateways that make up the internet backbone are called core gateways. Address Translation An organizations default gateway can also be used to “hide” the organizations internal IP addresses and keep them from being recognized on a public network. A public network is one that any user may access with little or no restrictions. On private networks, hiding IP addresses allows network managers more flexibility in assigning addresses. Clients behind a gateway may use any IP addressing scheme, regardless of whether it is recognized as legitimate by the Internet authorities but as soon as those devices need to go on the internet, they must have legitimate IP addresses to exchange data. When a clients transmission reaches the default gateway, the gateway opens the IP datagram and replaces the client’s private IP address with an Internet recognized IP address. This process is known as NAT (Network Address Translation). TCP/IP Mail Services All Internet mail services rely on the same principles of mail delivery, storage, and pickup, though they may use different types of software to accomplish these functions. Email servers and clients communicate through special TCP/IP application layer protocols. These protocols, all of which operate on a variety of operating systems are discussed below… SMTP (Simple Mail transfer Protocol) The protocol responsible for moving messages from one mail server to another over TCP/IP based networks. SMTP belongs to the application layer of the ODI model and relies on TCP as its transport protocol. Operates from port 25 on the SMTP server Simple sub-protocol, incapable of doing anything more than transporting mail or holding it in a queue MIME (Multipurpose Internet Mail Extensions) The standard message format specified by SMTP allows for lines that contain no more than 1000 ascii characters meaning if you relied solely on SMTP you would have very short messages and nothing like pictures included in an email. MIME us a standard for encoding and interpreting binary files, images, video, and non-ascii character sets within an email message. MIME identifies each element of a mail message according to content type. MIME does not replace SMTP but works in conjunction with it. Most modern email clients and servers support MIME POP (Post Office Protocol) POP is an application layer protocol used to retrieve messages from a mail server POP3 relies on TCP and operates over port 110 With POP3 mail is delivered and stored on a mail server until it is downloaded by a user Disadvantage of POP3 is that it typically does not allow users to save their messages on the server because of this IMAP is sometimes used IMAP (Internet Message Access Protocol) IMAP is a retrieval protocol that was developed as a more sophisticated alternative to POP3 The single biggest advantage IMAP4 has over POP3 is that users can store messages on the mail server, rather than having to continually download them Users can retrieve all or only a portion of any mail message Users can review their messages and delete them while the messages remain on the server Users can create sophisticated methods of organizing messages on the server Users can share a mailbox in a central location Disadvantages of IMAP are typically related to the fact that it requires more storage space on the server. Additional TCP/IP Utilities Nearly all TCP/IP utilities can be accessed from the command prompt on any type of server or client running TCP/IP. The syntaxt may differ depending on the OS of the client. Below is a list of additional TCP/IP utilities – research their use on your own! Ipconfig (Windows) & Ifconfig (Linux) Netstat Nbtstat Hostname, Host & Nslookup Dig (Linux) Whois (Linux) Traceroute (Tracert) Mtr (my traceroute) Route

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• Ubuntu 12.04. Compiz Failure. Computer has nothing to use

  - by Teddy

  I updated to Ubuntu 12.04 with Compiz..now Compiz is failing and I have no tool bars or ways of getting to applications except for firefox from a link presented from sending an error report. How am I supposed to: Fix this mess with no navigation to get to the terminal, or software center. When will this problem be fixed? When I updated the system why didn't it change me back to the crappy Unity interface (No offense). If it can't be fixed how do I get my files back?

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• SQL Server architecture - they want to move my database to new instance...Why?

  - by O'MALLEY

  Our current production database environment contains about 10 similarily managed databases. Our agency has just purchased and is installing new blade chasses and wants to move my database to a new instance (leaving the other 9 on another). This decision is being driven by one of our IT staff, not a DBA. I am a project manager, not a DBA but I know enough to not necesarrily have a good feeling about this decision and I am urging our IT department to make a sound decision based on what is best for the database. Our IT department has stated that it is not good to have all our eggs in one basket, and has also stated that my database contains "regulatory data" so it should be on its own instance. A couple of truths: - None of the databases on the current instance are OLTP databases nor are any of them data warehouses - My database currently has joins/views to a couple of the other databases in the production environment So my questions are as follows: Am I wrong to disregard a statement about eggs in baskets? (hello, this is why we have maintenance plans/disaster recovery plans). I'll mention that other databases also have regulatory data too. What types of questions do I need to ask to determine if this is a sound decicion? (A DBA friend mentioned that if the service level agreement of said database does not radically differ from the others then why do they want to do this?) I have done some research on linked servers. What arguments should I bring forth about the fact that I have views setup that rely on data from other DBs currently?

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• Are the National Computer Science Academy certifications worth it?

  - by Horacio Nuñez

  Hi to every one. I have a question regarding the real value of having NCSA's certifications. Today I reach their site and I easily passed the JavaScript certification within minutes, but I never reach questions related to Literal Javascript Notation (Json), closures or browser specific apis. This facts let me to doubt a bit of the real value of the test (and the proper certification you can have if you pay them $34), but maybe Im wrong and just earned a respected certification within the States for easy questions... in wich case I can spend some time doing other certifications on the same site. Did you have an NCSA certification and think is worth having it in your resume, or you know of a better certification program? thanks in advance, and looking forward to see your considerations.

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