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Articles indexed Friday February 11 2011

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  • SilverlightShow for Jan 31- Feb 06, 2011

    - by Dave Campbell
    Check out the Top Five most popular news at SilverlightShow for Jan 31- Feb 06, 2011. Here's SilverlightShow top 5 news for last week: Free ebook: Silverlight for Windows Phone Deploying Silverlight with WCF Services Localize a Silverlight 4 Application WCF - Silverlight debugging tips Kinect and WPF: Getting the raw and depth image using OpenNI Visit and bookmark SilverlightShow. Stay in the 'Light

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  • C#/.NET Little Wonders: The Concurrent Collections (1 of 3)

    - by James Michael Hare
    Once again we consider some of the lesser known classes and keywords of C#.  In the next few weeks, we will discuss the concurrent collections and how they have changed the face of concurrent programming. This week’s post will begin with a general introduction and discuss the ConcurrentStack<T> and ConcurrentQueue<T>.  Then in the following post we’ll discuss the ConcurrentDictionary<T> and ConcurrentBag<T>.  Finally, we shall close on the third post with a discussion of the BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. A brief history of collections In the beginning was the .NET 1.0 Framework.  And out of this framework emerged the System.Collections namespace, and it was good.  It contained all the basic things a growing programming language needs like the ArrayList and Hashtable collections.  The main problem, of course, with these original collections is that they held items of type object which means you had to be disciplined enough to use them correctly or you could end up with runtime errors if you got an object of a type you weren't expecting. Then came .NET 2.0 and generics and our world changed forever!  With generics the C# language finally got an equivalent of the very powerful C++ templates.  As such, the System.Collections.Generic was born and we got type-safe versions of all are favorite collections.  The List<T> succeeded the ArrayList and the Dictionary<TKey,TValue> succeeded the Hashtable and so on.  The new versions of the library were not only safer because they checked types at compile-time, in many cases they were more performant as well.  So much so that it's Microsoft's recommendation that the System.Collections original collections only be used for backwards compatibility. So we as developers came to know and love the generic collections and took them into our hearts and embraced them.  The problem is, thread safety in both the original collections and the generic collections can be problematic, for very different reasons. Now, if you are only doing single-threaded development you may not care – after all, no locking is required.  Even if you do have multiple threads, if a collection is “load-once, read-many” you don’t need to do anything to protect that container from multi-threaded access, as illustrated below: 1: public static class OrderTypeTranslator 2: { 3: // because this dictionary is loaded once before it is ever accessed, we don't need to synchronize 4: // multi-threaded read access 5: private static readonly Dictionary<string, char> _translator = new Dictionary<string, char> 6: { 7: {"New", 'N'}, 8: {"Update", 'U'}, 9: {"Cancel", 'X'} 10: }; 11:  12: // the only public interface into the dictionary is for reading, so inherently thread-safe 13: public static char? Translate(string orderType) 14: { 15: char charValue; 16: if (_translator.TryGetValue(orderType, out charValue)) 17: { 18: return charValue; 19: } 20:  21: return null; 22: } 23: } Unfortunately, most of our computer science problems cannot get by with just single-threaded applications or with multi-threading in a load-once manner.  Looking at  today's trends, it's clear to see that computers are not so much getting faster because of faster processor speeds -- we've nearly reached the limits we can push through with today's technologies -- but more because we're adding more cores to the boxes.  With this new hardware paradigm, it is even more important to use multi-threaded applications to take full advantage of parallel processing to achieve higher application speeds. So let's look at how to use collections in a thread-safe manner. Using historical collections in a concurrent fashion The early .NET collections (System.Collections) had a Synchronized() static method that could be used to wrap the early collections to make them completely thread-safe.  This paradigm was dropped in the generic collections (System.Collections.Generic) because having a synchronized wrapper resulted in atomic locks for all operations, which could prove overkill in many multithreading situations.  Thus the paradigm shifted to having the user of the collection specify their own locking, usually with an external object: 1: public class OrderAggregator 2: { 3: private static readonly Dictionary<string, List<Order>> _orders = new Dictionary<string, List<Order>>(); 4: private static readonly _orderLock = new object(); 5:  6: public void Add(string accountNumber, Order newOrder) 7: { 8: List<Order> ordersForAccount; 9:  10: // a complex operation like this should all be protected 11: lock (_orderLock) 12: { 13: if (!_orders.TryGetValue(accountNumber, out ordersForAccount)) 14: { 15: _orders.Add(accountNumber, ordersForAccount = new List<Order>()); 16: } 17:  18: ordersForAccount.Add(newOrder); 19: } 20: } 21: } Notice how we’re performing several operations on the dictionary under one lock.  With the Synchronized() static methods of the early collections, you wouldn’t be able to specify this level of locking (a more macro-level).  So in the generic collections, it was decided that if a user needed synchronization, they could implement their own locking scheme instead so that they could provide synchronization as needed. The need for better concurrent access to collections Here’s the problem: it’s relatively easy to write a collection that locks itself down completely for access, but anything more complex than that can be difficult and error-prone to write, and much less to make it perform efficiently!  For example, what if you have a Dictionary that has frequent reads but in-frequent updates?  Do you want to lock down the entire Dictionary for every access?  This would be overkill and would prevent concurrent reads.  In such cases you could use something like a ReaderWriterLockSlim which allows for multiple readers in a lock, and then once a writer grabs the lock it blocks all further readers until the writer is done (in a nutshell).  This is all very complex stuff to consider. Fortunately, this is where the Concurrent Collections come in.  The Parallel Computing Platform team at Microsoft went through great pains to determine how to make a set of concurrent collections that would have the best performance characteristics for general case multi-threaded use. Now, as in all things involving threading, you should always make sure you evaluate all your container options based on the particular usage scenario and the degree of parallelism you wish to acheive. This article should not be taken to understand that these collections are always supperior to the generic collections. Each fills a particular need for a particular situation. Understanding what each container is optimized for is key to the success of your application whether it be single-threaded or multi-threaded. General points to consider with the concurrent collections The MSDN points out that the concurrent collections all support the ICollection interface. However, since the collections are already synchronized, the IsSynchronized property always returns false, and SyncRoot always returns null.  Thus you should not attempt to use these properties for synchronization purposes. Note that since the concurrent collections also may have different operations than the traditional data structures you may be used to.  Now you may ask why they did this, but it was done out of necessity to keep operations safe and atomic.  For example, in order to do a Pop() on a stack you have to know the stack is non-empty, but between the time you check the stack’s IsEmpty property and then do the Pop() another thread may have come in and made the stack empty!  This is why some of the traditional operations have been changed to make them safe for concurrent use. In addition, some properties and methods in the concurrent collections achieve concurrency by creating a snapshot of the collection, which means that some operations that were traditionally O(1) may now be O(n) in the concurrent models.  I’ll try to point these out as we talk about each collection so you can be aware of any potential performance impacts.  Finally, all the concurrent containers are safe for enumeration even while being modified, but some of the containers support this in different ways (snapshot vs. dirty iteration).  Once again I’ll highlight how thread-safe enumeration works for each collection. ConcurrentStack<T>: The thread-safe LIFO container The ConcurrentStack<T> is the thread-safe counterpart to the System.Collections.Generic.Stack<T>, which as you may remember is your standard last-in-first-out container.  If you think of algorithms that favor stack usage (for example, depth-first searches of graphs and trees) then you can see how using a thread-safe stack would be of benefit. The ConcurrentStack<T> achieves thread-safe access by using System.Threading.Interlocked operations.  This means that the multi-threaded access to the stack requires no traditional locking and is very, very fast! For the most part, the ConcurrentStack<T> behaves like it’s Stack<T> counterpart with a few differences: Pop() was removed in favor of TryPop() Returns true if an item existed and was popped and false if empty. PushRange() and TryPopRange() were added Allows you to push multiple items and pop multiple items atomically. Count takes a snapshot of the stack and then counts the items. This means it is a O(n) operation, if you just want to check for an empty stack, call IsEmpty instead which is O(1). ToArray() and GetEnumerator() both also take snapshots. This means that iteration over a stack will give you a static view at the time of the call and will not reflect updates. Pushing on a ConcurrentStack<T> works just like you’d expect except for the aforementioned PushRange() method that was added to allow you to push a range of items concurrently. 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: // but you can also push multiple items in one atomic operation (no interleaves) 7: stack.PushRange(new [] { "Second", "Third", "Fourth" }); For looking at the top item of the stack (without removing it) the Peek() method has been removed in favor of a TryPeek().  This is because in order to do a peek the stack must be non-empty, but between the time you check for empty and the time you execute the peek the stack contents may have changed.  Thus the TryPeek() was created to be an atomic check for empty, and then peek if not empty: 1: // to look at top item of stack without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (stack.TryPeek(out item)) 5: { 6: Console.WriteLine("Top item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Stack was empty."); 11: } Finally, to remove items from the stack, we have the TryPop() for single, and TryPopRange() for multiple items.  Just like the TryPeek(), these operations replace Pop() since we need to ensure atomically that the stack is non-empty before we pop from it: 1: // to remove items, use TryPop or TryPopRange to get multiple items atomically (no interleaves) 2: if (stack.TryPop(out item)) 3: { 4: Console.WriteLine("Popped " + item); 5: } 6:  7: // TryPopRange will only pop up to the number of spaces in the array, the actual number popped is returned. 8: var poppedItems = new string[2]; 9: int numPopped = stack.TryPopRange(poppedItems); 10:  11: foreach (var theItem in poppedItems.Take(numPopped)) 12: { 13: Console.WriteLine("Popped " + theItem); 14: } Finally, note that as stated before, GetEnumerator() and ToArray() gets a snapshot of the data at the time of the call.  That means if you are enumerating the stack you will get a snapshot of the stack at the time of the call.  This is illustrated below: 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: var results = stack.GetEnumerator(); 7:  8: // but you can also push multiple items in one atomic operation (no interleaves) 9: stack.PushRange(new [] { "Second", "Third", "Fourth" }); 10:  11: while(results.MoveNext()) 12: { 13: Console.WriteLine("Stack only has: " + results.Current); 14: } The only item that will be printed out in the above code is "First" because the snapshot was taken before the other items were added. This may sound like an issue, but it’s really for safety and is more correct.  You don’t want to enumerate a stack and have half a view of the stack before an update and half a view of the stack after an update, after all.  In addition, note that this is still thread-safe, whereas iterating through a non-concurrent collection while updating it in the old collections would cause an exception. ConcurrentQueue<T>: The thread-safe FIFO container The ConcurrentQueue<T> is the thread-safe counterpart of the System.Collections.Generic.Queue<T> class.  The concurrent queue uses an underlying list of small arrays and lock-free System.Threading.Interlocked operations on the head and tail arrays.  Once again, this allows us to do thread-safe operations without the need for heavy locks! The ConcurrentQueue<T> (like the ConcurrentStack<T>) has some departures from the non-concurrent counterpart.  Most notably: Dequeue() was removed in favor of TryDequeue(). Returns true if an item existed and was dequeued and false if empty. Count does not take a snapshot It subtracts the head and tail index to get the count.  This results overall in a O(1) complexity which is quite good.  It’s still recommended, however, that for empty checks you call IsEmpty instead of comparing Count to zero. ToArray() and GetEnumerator() both take snapshots. This means that iteration over a queue will give you a static view at the time of the call and will not reflect updates. The Enqueue() method on the ConcurrentQueue<T> works much the same as the generic Queue<T>: 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5: queue.Enqueue("Second"); 6: queue.Enqueue("Third"); For front item access, the TryPeek() method must be used to attempt to see the first item if the queue.  There is no Peek() method since, as you’ll remember, we can only peek on a non-empty queue, so we must have an atomic TryPeek() that checks for empty and then returns the first item if the queue is non-empty. 1: // to look at first item in queue without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (queue.TryPeek(out item)) 5: { 6: Console.WriteLine("First item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Queue was empty."); 11: } Then, to remove items you use TryDequeue().  Once again this is for the same reason we have TryPeek() and not Peek(): 1: // to remove items, use TryDequeue. If queue is empty returns false. 2: if (queue.TryDequeue(out item)) 3: { 4: Console.WriteLine("Dequeued first item " + item); 5: } Just like the concurrent stack, the ConcurrentQueue<T> takes a snapshot when you call ToArray() or GetEnumerator() which means that subsequent updates to the queue will not be seen when you iterate over the results.  Thus once again the code below will only show the first item, since the other items were added after the snapshot. 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5:  6: var iterator = queue.GetEnumerator(); 7:  8: queue.Enqueue("Second"); 9: queue.Enqueue("Third"); 10:  11: // only shows First 12: while (iterator.MoveNext()) 13: { 14: Console.WriteLine("Dequeued item " + iterator.Current); 15: } Using collections concurrently You’ll notice in the examples above I stuck to using single-threaded examples so as to make them deterministic and the results obvious.  Of course, if we used these collections in a truly multi-threaded way the results would be less deterministic, but would still be thread-safe and with no locking on your part required! For example, say you have an order processor that takes an IEnumerable<Order> and handles each other in a multi-threaded fashion, then groups the responses together in a concurrent collection for aggregation.  This can be done easily with the TPL’s Parallel.ForEach(): 1: public static IEnumerable<OrderResult> ProcessOrders(IEnumerable<Order> orderList) 2: { 3: var proxy = new OrderProxy(); 4: var results = new ConcurrentQueue<OrderResult>(); 5:  6: // notice that we can process all these in parallel and put the results 7: // into our concurrent collection without needing any external locking! 8: Parallel.ForEach(orderList, 9: order => 10: { 11: var result = proxy.PlaceOrder(order); 12:  13: results.Enqueue(result); 14: }); 15:  16: return results; 17: } Summary Obviously, if you do not need multi-threaded safety, you don’t need to use these collections, but when you do need multi-threaded collections these are just the ticket! The plethora of features (I always think of the movie The Three Amigos when I say plethora) built into these containers and the amazing way they acheive thread-safe access in an efficient manner is wonderful to behold. Stay tuned next week where we’ll continue our discussion with the ConcurrentBag<T> and the ConcurrentDictionary<TKey,TValue>. For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here.   Tweet Technorati Tags: C#,.NET,Concurrent Collections,Collections,Multi-Threading,Little Wonders,BlackRabbitCoder,James Michael Hare

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  • DEEP DIVE MVVM at #MIX11

    - by Laurent Bugnion
    The public (you!) has spoken, and “Deep Dive MVVM” was selected (along with 11 other open call talks) out of 217 proposals. There were 17’000 votes! These are pretty amazing numbers, and believe me when I tell you that I still didn’t completely realize what just happened! I want to really underline the outstanding quality of many of the talks that were proposed. I decided not to reveal my votes, because I just know too many of the candidates and I had only 10 votes but let’s just say that some of my favorites were picked, and some were not, and I really wish that I can see them all either at MIX or in another conference. I already started putting down ideas for the talk (not too many, because I didn’t want to jinx it) and it should be a really great session. We will, as the title shows, dive deep into the subtleties of MVVM, and explore some techniques that allow to overcome some of the hurdles presented by this pattern. This session will be shaped by many emails that I received over the past year, since “Understanding the MVVM pattern” was presented, and offered, for many, a first look into Model-View-ViewModel. So now’s the chance, comment and let me know what topics you would like to discuss. If you had not done so before, go ahead and watch last year’s session, it will be a great preparation. Let’s talk real life development, let’s explore the problems and find solutions. I already have a nice collection of emails asking questions around MVVM and my goal is to answer as many as I can. Leave a comment and I will do my best to answer these as well. The date/time was not announced yet, so watch this space for details. I am really looking forward to seeing many of you in Las Vegas, and for those who cannot make it, don’t worry, all the sessions will be published in video by the amazing MIX team a few hours after the session actually takes place. Thanks for your confidence and in the meantime, Happy Coding! Laurent Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • How do I improve my incremental-backup performance?

    - by Alistair Bell
    I'm currently using the traditional rsync+cp -al method to create incremental/snapshot backups of our server tree. The backups are going onto a pair of eight-disk towers connected to the backup machine (a Sandy Bridge machine with 16 GB of RAM, running CentOS 5.5) via four eSATA connections (four disks per connection). Each disk is a regular 2 TB disk, so we have 32 TB of disk space connected to the backup machine. We're backing up about 20 TB of data on the servers with this. The problem is that each daily backup is taking more than 24 hours, and the real time-killer isn't the actual rsync, but the time it takes to perform a cp -al of the tree locally on the backup machine. It's taking more than 12 hours just to make the shadow copy of the tree, and as far as I can tell the performance backlog is at the disk (top shows the cp using a lot of RAM but not a lot of CPU and mostly in uninterruptible-sleep state) We have the server data split into four major volumes (and a few minor ones), and each of these backups runs in parallel (with some offsets in the cron to try to get some disks' cp done first). There are two volumes on the backup drive, both striped LVM volumes of 16 TB each. So obviously I need to improve the performance because it's unusable as it stands. The first question is: when CentOS 6 comes out, with support for btrfs, will making snapshots of subvolumes with btrfs substantially increase this performance? The second is: is there a way, with ext3 or something else supported in CentOS 5 or 6, to 'encourage' it to put the directories/inodes in one part of a volume (which could happen to be the part that's on an SSD, via LVM) and the files in another? That would presumably solve the problem, but I don't know of ways to hint ext3 like that.

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  • Replication in PG 9 between Windows and Linux boxes

    - by mlaverd
    I have PostgreSQL 9 running on Windows 2003 SP2. I am trying to replicate it on a Fedora 12 system running PostgreSQL 9 as well. I am hitting this error message: /usr/pgsql-9.0/bin/postgres -D /var/lib/pgsql/9.0/data/ -p 5432 2011-02-11 17:43:26 ISTFATAL: incorrect checksum in control file Because of firewall restrictions, I could not follow the official instructions to the letter. Instead, I zipped the contents of the data directory when the server was offline and copied that to the Linux box. I ran a sha1deep on both directories and there were no mismatches. I changed the rights so that only the postgres user and group had access to the files. Now, what can I do for replication to work? I tried with a 'pg_dumpall', but the system complains that the database IDs do no match.

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  • MSSQL 2008 License for both Web application and desktop application

    - by Bayonian
    I have ASP.NET web application using MSSQL express at the moment. But I want to use MSSQL 2008. But I'm NOT sure about what kind of license I should buy. I'm considering the Processor License according to this document. I'm not sure if it's the right choice. If I buy User CAL. should I buy only 1 CAL for my web application? or for all visitors who visit my web site? I also have a Windows desktop application that write/read data from the server. Do I need a seperate license with for this Windows application if I buy Processor License. Thank you for suggestion.

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  • Is it possible to run two servers in one system ?

    - by srikanth
    hi, i have a small problem while trying to execute the wamp server. At present in my system i am running Apache server. i have a php application. for that i am trying to install wamp server in my system. wamp server is not running. i change the port no of wamp server as : in my C:\wamp\bin\apache\Apache2.2.11\conf\ i have httpd.conf file. in that i change listener and host name with another port no. then also it is not working. any one can you help me......... plz...

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  • In WHM - Addon Domain Matches Primary Domain From Separate Account - I can't delete the addon domain

    - by Joshua Riddle
    I have an account (domian1.com) with the an addon domain (domain2.com) that matches the primary domain (domain2.com) of a separate account. I believe it was created renaming the primary domain of the second account. I want to delete the addon domain from domain1.com. However when I try i get the error: Error from park wrapper: Sorry, you do not control the domain domain2.com Ive tried all the methods in other forum posts and have been unable to successfully remove the addon domain and subdomain from domain1.com. Thanks in advance for all the great input!

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  • WBadmin script to backup System State into another partition failed ?

    - by Albert Widjaja
    Hi Everyone, I tried numerous time but it is still failed like the following script on cmd prompt. Is there any way to create automated script to backup system state on my Windows Server 2008 using WBAdmin into D drive inside a directory ? any help would be greatly appreciated. C:\Users\Administratorwbadmin START SYSTEMSTATEBACKUP -backuptarget:D:\Admin\Backup wbadmin 1.0 - Backup command-line tool (C) Copyright 2004 Microsoft Corp. Starting System State Backup [12/02/2011 4:22 AM] Retrieving volume information... This would backup the system state from volume(s) SYS(C:) to D:\Admin\Backup. Do you want to start the backup operation? [Y] Yes [N] No Y ERROR - Specified backup location could not be found. C:\Users\Administratorwbadmin START SYSTEMSTATEBACKUP -backuptarget:D:\Admin wbadmin 1.0 - Backup command-line tool (C) Copyright 2004 Microsoft Corp. Starting System State Backup [12/02/2011 4:22 AM] Retrieving volume information... This would backup the system state from volume(s) SYS(C:) to D:\Admin. Do you want to start the backup operation? [Y] Yes [N] No Y ERROR - Specified backup location could not be found. C:\Users\Administratorwbadmin START SYSTEMSTATEBACKUP -backuptarget:"D:\Admin\Backup" -quiet wbadmin 1.0 - Backup command-line tool (C) Copyright 2004 Microsoft Corp. Starting System State Backup [12/02/2011 4:23 AM] Retrieving volume information... This would backup the system state from volume(s) SYS(C:) to D:\Admin\Backup. ERROR - Specified backup location could not be found. C:\Users\Administratorwbadmin START SYSTEMSTATEBACKUP -backuptarget:D:\ -quiet wbadmin 1.0 - Backup command-line tool (C) Copyright 2004 Microsoft Corp. Starting System State Backup [12/02/2011 4:23 AM] Retrieving volume information... This would backup the system state from volume(s) SYS(C:) to D:. ERROR - Specified backup location could not be found. C:\Users\Administrator

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  • Connect two subnets without router

    - by Shcheklein
    I got two Comcast routers with two different subnets on each. Every subnet contains 5 static IPs. Two questions: Are there any problems if both routers and machines from both subnets are connected into one switch? Security issues doesn't matter there. I need to know if there are some performance or other problems. Is it possible to make machines from different subnets to see each other if they all are connected into one switch? Some static routing, add ARP records or somethig else ... I just want to avoid configuring second ethernet adaptors, third router or something. And I need to connect these subnets vai high-speed local network.

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  • Centos Virtual host loading default page

    - by ntechi
    I have asked a question which was related to this but not same, I have a centos VPS, which has two wordpress websites, one is mbas.co.in and another is onlinemba123.com, now for virtual hosting using just ONE IP ADDRESS, first I started mbas.co.in, which is working fine, when I added onlinemba123.com then, it is loading default Centos page instead of my website, and I am just testing my onlinemba123 website, I haven't configured DNS for it, I am testing it through editing my PC's hosts file, My website folder names are also same as in the conf file below Now my question is how can I load my website instead of Default page, is my virtual host config fine? My virtual host config: NameVirtualHost *:80 <VirtualHost *:80> ServerAdmin [email protected] DocumentRoot /var/www/html/www.mbas.co.in ServerName mbas.co.in ErrorLog logs/mbas.co.in-error_log CustomLog logs/mbas.co.in-access_log common </VirtualHost> <VirtualHost *:80> ServerAdmin [email protected] DocumentRoot /var/www/html/www.onlinemba123.com ServerName www.onlinemba123.com ErrorLog logs/onlinemba123-error_log CustomLog logs/onlinemba123-access_log common </VirtualHost> My computers host file is: xx.xxx.xxx.xxx www.onlinemba123.com

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  • Multiple VLANs, multiple subnets, single DHCP server?

    - by EightQuarterBit
    Hey guys! At my job we are prepping to transition from multiple LANs connected over slow VPN connections to a single MAN connected over fiber, and I've got a few questions. First of all, we are planning on making each physical site its own VLAN, but we would like to have a single DHCP server at the data center hand out IPs to each VLAN. We've pretty much got the VLAN tagging structure all worked out, but we would like to have our single DHCP server assign different subnets of IPs to each VLAN. For instance, VLAN 2 gets 10.0.2.x through 10.0.4.x, VLAN 3 gets 10.0.5.x through 10.0.7.x etc. We are an Active Directory based shop and we have a Server 2003 box handling DHCP (though we aren't averse to upgrading it to server 2008.) Is this feasible, or am I pipe-dreaming?

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  • Syn_Recievd on port 80 , IIS 7.5

    - by Ashian
    Hi I have a trouble on my windows 2008 server. I host several web site on it. From some days ago, my web sites stop responding on port 80 after a while. In this time I can't access web sites from local machine and from remote. I can also browse websites on other ports ( custom port that I set) I find that I have many Syn_Received status on netstat. And when web sites stop, I got only syn_received on port 80. I have to restart server because when I try to restart IIS , it takes a long time to stop W3SVC and many times it doesn’t stop at all. Would anyone please tell me : - How can I manage Syn Attack ? Thanks

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  • Virtualbox, Virtual guest OS issue

    - by user70370
    Hi, My host OS is: Ubuntu 10.10. One of my virtual OS is: Ubuntu 9.04 and another one is: Ubuntu 10.04. All of these virtualisation has been completed with Virtualbox. Now, I need to replicate those two servers, one server is running in Ubuntu 9.04 and another one is running in Ubuntu 10.04. Is it possible? If yes, can you please provide me some help? So, in short words, the whole thing is: Host: Ubuntu 10.10 Guest 1: Ubuntu 9.04 Guest 2: Ubuntu 10.04 Job: Must have to run two guests at a time. Because, two LDAP of two guests need to replicate. Now, If I try to get the first Guest ( hostname: mohib-laptop ) from second Guest ( hostname: zaman-laptop ), it is not getting! Do I need to change IP address of those both Guests? Or are there anything which will make it possible?

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  • creating a new user Ubuntu

    - by Matt
    I am trying to new user that can sftp on a server....i did this [email protected]:~$ sudo useradd jesse -p testPass [email protected]:~$ sudo passwd jesse Enter new UNIX password: Retype new UNIX password: passwd: password updated successfully but when i try to login via sftp I cant get in....am i missing something like adding a group or something the answer was PasswordAuthentication yes

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  • Data transfer to my own computer from a website host by the same computer

    - by gunbuster363
    Hi all, I have a question about using a web site host in my computer, say Computer A, using any web server hosting application e.g : apache. I connect to my website in my very same computer A, and request to download a file of size 1Mb, in otherwords, I am connecting to my own computer and want to download a file in my computer. In addition, my internet access is bound by a proxy server in a way of gateway. The questions are - does the file transfer really exist? Or is it a local file copying between 2 location? Will my data packet go through the proxy, to the internet, and go back to the proxy and return to me? Thanks everyone who are watching this question.

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  • How to get .cgi files working in python with Apache on Ubuntu

    - by tapan
    I am not really sure whether to post this here or on SO. I think this has more to do with server administration so i am posting it here. I have apache 2.2 installed on my ubuntu 10.10 system with libapache2-mod-python. However when i put a .cgi file with python in it in my apache root (/var/www) it doesn't get executed and all i see is the script i have written. For example this should show the text "Test": #!/usr/bin/python print "Test" However the above script shows up in my browser. Any idea what conf files,etc. i'll have to go through and change to allow this to work ? (the file perms on test.cgi is 755 if that makes a difference.)

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  • Two Network Adapters on Hyper-V Host - Best way to configure?

    - by GoNorthWest
    Hi, I have two physical network adapters installed in my Hyper-V host. I want one to be dedicated to the host, and the other to provide external network services to the VMs. Would the appropriate configuration be as such: Leave the first physical network adapter alone, assigning it the host IP, but not using it to create any Virtual Netorks For the second physical adapter, I would create an External Network, along with a Microsoft Virtual Switch, and use that to provide network services to the VMs. Each virtual NIC for the VM would be associated with that External Network. A static IP would be assigned to this adapter, and each VM would be assigned a static IP as well. The above seems reasonable to me, but I'm not sure if it's correct. Does anyone have any thoughts? Thanks! Mark

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  • windows PATH not working for network drive

    - by Brendan Abel
    I'm using an autorun.bat to append some directory paths to the Windows PATH variable so that I can use a few tools and bat scripts within cmd.exe I'm running into a problem where the above isn't working on a network drive. Ex. Using a program called mycmd.exe Ex.1 (this works) C:\folder\mycmd.exe SET PATH=%PATH%;C:\folder Ex. 2 (doesn't work) H:\folder\mycmd.exe SET PATH=%PATH%;H:\folder

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  • Creating Shared Wifi Connection on Windows 7 WITHOUT wep/wpa security?

    - by Duncan
    Ok, for some reason I just can't figure this out on Windows 7. Never had an issue with it on Windows XP, never tried in Vista. I realize that I need to create an Ad-Hoc setup which I can do. However I can't get it to share the wireless signal on my laptop. Even if I go into the adapter settings. I need (well, want) to connect my old Psion netBook to my home network and due to the wireless card, I can't have any form of security. Thanks in advance!

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  • MSSQL 2008 License for both Web application and desktop application [closed]

    - by Angkor Wat
    I have ASP.NET web application using MSSQL express at the moment. But I want to use MSSQL 2008. But I'm NOT sure about what kind of license I should buy. I'm considering the Processor License according to this document. I'm not sure if it's the right choice. If I buy User CAL. should I buy only 1 CAL for my web application? or for all visitors who visit my web site? I also have a Windows desktop application that write/read data from the server. Do I need a seperate license with for this Windows application if I buy Processor License. Thank you for suggestion.

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  • How do I restore a non-system hard drive using Time Machine under OSX?

    - by richardtallent
    I dropped one of the external drives on my Mac Pro and it started making noises... so I bought a replacement drive. No biggie, that's why I have Time Machine, right? So now that I have the new drive up and initialized, how do I actually restore the drive from backup? Time Machine is intuitive when it comes to restoring the system drive or restoring individual folders/files on the same literal device, but I'm a bit stuck in how to properly restore an entire drive that is not the boot drive. I saw one suggestion to use the same volume name as the old drive and then go into Time Machine. Haven't tried that since the information is unconfirmed. For now, I just went to the Time Machine volume, found the latest backup folder for that volume, and I'm copying the files via Finder. Of couse, I expect this to work just fine, but I feel like I'm missing something if that's the "proper" way to do this.

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  • Utility to unmap a network drive when the screen saver starts

    - by JimR
    I'm looking for a way to unmap network drives when the screen saver turns on. I have a few users that share an external, encrypted drive (Samba share, not windows) and they have a requirement to disconnect the drive mapping when the local machine is idle. I'd also like it to warn them if there are open files on the mapped drive, if possible. There is also a requirement to force the password to be reentered before mapping when the machine comes back from idle. Is there a Windows setting or utility out there in the wild that meets these requirements?

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  • Best way to send large files point-to-point?

    - by Adam S
    I'm looking for a way to send a 10GB file to a friend. I really need to send it over the internet, but e-mail or uploading sites are not really an option. I remember using MSN messenger and having a file transfer feature that worked decently well. However, my friend doesn't have this software and doesn't want to get it. I know that the professional versions of TeamViewer have such a feature, but are there any free alternatives?

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  • no display on tv when connecting pc via hdmi in win7

    - by Kane
    The system of pc is win7 32bit, the video card is ATI 4670. The tv is philips 74xx series. And the monitor is Dell 19' that connect with pc via VGA. The tv can receive the singal and show the pictures when booting the pc(bios self checking, the logo of windows 7), however the tv says there is no signal after the win7 login window shows. I have installed the latest CCC and driver of ATI video card. Does anyone have idea for it?

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