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• Organization &amp; Architecture UNISA Studies &ndash; Chap 5

  - by MarkPearl

  Learning Outcomes Describe the operation of a memory cell Explain the difference between DRAM and SRAM Discuss the different types of ROM Explain the concepts of a hard failure and a soft error respectively Describe SDRAM organization Semiconductor Main Memory The two traditional forms of RAM used in computers are DRAM and SRAM DRAM (Dynamic RAM) Divided into two technologies… Dynamic Static Dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge in a capacitor is interpreted as a binary 1 or 0. Because capacitors have natural tendency to discharge, dynamic RAM requires periodic charge refreshing to maintain data storage. The term dynamic refers to the tendency of the stored charge to leak away, even with power continuously applied. Although the DRAM cell is used to store a single bit (0 or 1), it is essentially an analogue device. The capacitor can store any charge value within a range, a threshold value determines whether the charge is interpreted as a 1 or 0. SRAM (Static RAM) SRAM is a digital device that uses the same logic elements used in the processor. In SRAM, binary values are stored using traditional flip flop logic configurations. SRAM will hold its data as along as power is supplied to it. Unlike DRAM, no refresh is required to retain data. SRAM vs. DRAM DRAM is simpler and smaller than SRAM. Thus it is more dense and less expensive than SRAM. The cost of the refreshing circuitry for DRAM needs to be considered, but if the machine requires a large amount of memory, DRAM turns out to be cheaper than SRAM. SRAMS are somewhat faster than DRAM, thus SRAM is generally used for cache memory and DRAM is used for main memory. Types of ROM Read Only Memory (ROM) contains a permanent pattern of data that cannot be changed. ROM is non volatile meaning no power source is required to maintain the bit values in memory. While it is possible to read a ROM, it is not possible to write new data into it. An important application of ROM is microprogramming, other applications include library subroutines for frequently wanted functions, System programs, Function tables. A ROM is created like any other integrated circuit chip, with the data actually wired into the chip as part of the fabrication process. To reduce costs of fabrication, we have PROMS. PROMS are… Written only once Non-volatile Written after fabrication Another variation of ROM is the read-mostly memory, which is useful for applications in which read operations are far more frequent than write operations, but for which non volatile storage is required. There are three common forms of read-mostly memory, namely… EPROM EEPROM Flash memory Error Correction Semiconductor memory is subject to errors, which can be classed into two categories… Hard failure – Permanent physical defect so that the memory cell or cells cannot reliably store data Soft failure – Random error that alters the contents of one or more memory cells without damaging the memory (common cause includes power supply issues, etc.) Most modern main memory systems include logic for both detecting and correcting errors. Error detection works as follows… When data is to be read into memory, a calculation is performed on the data to produce a code Both the code and the data are stored When the previously stored word is read out, the code is used to detect and possibly correct errors The error checking provides one of 3 possible results… No errors are detected – the fetched data bits are sent out An error is detected, and it is possible to correct the error. The data bits plus error correction bits are fed into a corrector, which produces a corrected set of bits to be sent out An error is detected, but it is not possible to correct it. This condition is reported Hamming Code See wiki for detailed explanation. We will probably need to know how to do a hemming code – refer to the textbook (pg. 188 – 189) Advanced DRAM organization One of the most critical system bottlenecks when using high-performance processors is the interface to main memory. This interface is the most important pathway in the entire computer system. The basic building block of main memory remains the DRAM chip. In recent years a number of enhancements to the basic DRAM architecture have been explored, and some of these are now on the market including… SDRAM (Synchronous DRAM) DDR-DRAM RDRAM SDRAM (Synchronous DRAM) SDRAM exchanges data with the processor synchronized to an external clock signal and running at the full speed of the processor/memory bus without imposing wait states. SDRAM employs a burst mode to eliminate the address setup time and row and column line precharge time after the first access In burst mode a series of data bits can be clocked out rapidly after the first bit has been accessed SDRAM has a multiple bank internal architecture that improves opportunities for on chip parallelism SDRAM performs best when it is transferring large blocks of data serially There is now an enhanced version of SDRAM known as double data rate SDRAM or DDR-SDRAM that overcomes the once-per-cycle limitation of SDRAM

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• InnoDB Compression Improvements in MySQL 5.6

  - by Inaam Rana

  MySQL 5.6 comes with significant improvements for the compression support inside InnoDB. The enhancements that we'll talk about in this piece are also a good example of community contributions. The work on these was conceived, implemented and contributed by the engineers at Facebook. Before we plunge into the details let us familiarize ourselves with some of the key concepts surrounding InnoDB compression. In InnoDB compressed pages are fixed size. Supported sizes are 1, 2, 4, 8 and 16K. The compressed page size is specified at table creation time. InnoDB uses zlib for compression. InnoDB buffer pool will attempt to cache compressed pages like normal pages. However, whenever a page is actively used by a transaction, we'll always have the uncompressed version of the page as well i.e.: we can have a page in the buffer pool in compressed only form or in a state where we have both the compressed page and uncompressed version but we'll never have a page in uncompressed only form. On-disk we'll always only have the compressed page. When both compressed and uncompressed images are present in the buffer pool they are always kept in sync i.e.: changes are applied to both atomically. Recompression happens when changes are made to the compressed data. In order to minimize recompressions InnoDB maintains a modification log within a compressed page. This is the extra space available in the page after compression and it is used to log modifications to the compressed data thus avoiding recompressions. DELETE (and ROLLBACK of DELETE) and purge can be performed without recompressing the page. This is because the delete-mark bit and the system fields DB_TRX_ID and DB_ROLL_PTR are stored in uncompressed format on the compressed page. A record can be purged by shuffling entries in the compressed page directory. This can also be useful for updates of indexed columns, because UPDATE of a key is mapped to INSERT+DELETE+purge. A compression failure happens when we attempt to recompress a page and it does not fit in the fixed size. In such case, we first try to reorganize the page and attempt to recompress and if that fails as well then we split the page into two and recompress both pages. Now lets talk about the three major improvements that we made in MySQL 5.6.Logging of Compressed Page Images:InnoDB used to log entire compressed data on the page to the redo logs when recompression happens. This was an extra safety measure to guard against the rare case where an attempt is made to do recovery using a different zlib version from the one that was used before the crash. Because recovery is a page level operation in InnoDB we have to be sure that all recompress attempts must succeed without causing a btree page split. However, writing entire compressed data images to the redo log files not only makes the operation heavy duty but can also adversely affect flushing activity. This happens because redo space is used in a circular fashion and when we generate much more than normal redo we fill up the space much more quickly and in order to reuse the redo space we have to flush the corresponding dirty pages from the buffer pool.Starting with MySQL 5.6 a new global configuration parameter innodb_log_compressed_pages. The default value is true which is same as the current behavior. If you are sure that you are not going to attempt to recover from a crash using a different version of zlib then you should set this parameter to false. This is a dynamic parameter.Compression Level:You can now set the compression level that zlib should choose to compress the data. The global parameter is innodb_compression_level - the default value is 6 (the zlib default) and allowed values are 1 to 9. Again the parameter is dynamic i.e.: you can change it on the fly.Dynamic Padding to Reduce Compression Failures:Compression failures are expensive in terms of CPU. We go through the hoops of recompress, failure, reorganize, recompress, failure and finally page split. At the same time, how often we encounter compression failure depends largely on the compressibility of the data. In MySQL 5.6, courtesy of Facebook engineers, we have an adaptive algorithm based on per-index statistics that we gather about compression operations. The idea is that if a certain index/table is experiencing too many compression failures then we should try to pack the 16K uncompressed version of the page less densely i.e.: we let some space in the 16K page go unused in an attempt that the recompression won't end up in a failure. In other words, we dynamically keep adding 'pad' to the 16K page till we get compression failures within an agreeable range. It works the other way as well, that is we'll keep removing the pad if failure rate is fairly low. To tune the padding effort two configuration variables are exposed. innodb_compression_failure_threshold_pct: default 5, range 0 - 100,dynamic, implies the percentage of compress ops to fail before we start using to padding. Value 0 has a special meaning of disabling the padding. innodb_compression_pad_pct_max: default 50, range 0 - 75, dynamic, the  maximum percentage of uncompressed data page that can be reserved as pad.

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• Pagination links broken - php/jquery

  - by ClarkSKent

  Hey, I'm still trying to get my pagination links to load properly dynamically. But I can't seem to find a solution to this one problem. vote down star Hi everyone, I am still trying to figure out how to fix my pagination script to work properly. the problem I am having is when I click any of the pagination number links to go the next page, the new content does not load. literally nothing happens and when looking at the console in Firebug, nothing is sent or loaded. I have on the main page 3 links to filter the content and display it. When any of these links are clicked the results are loaded and displayed along with the associated pagination numbers for that specific content. I believe the problem is coming from the sql query in generate_pagination.php (seen below). When I hard code the sql category part it works, but is not dynamic at all. This is why I'm calling $ids=$_GET['ids']; and trying to put that into the category section but then the numbers don't display at all. If I echo out the $ids variable and click on a filter it does display the correct name/id, so I don't know why this doesn't work Here is the main page so you can see how I am including and starting the function(I'm new to php): <?php include_once('generate_pagination.php'); ?> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js"></script> <script type="text/javascript" src="jquery_pagination.js"></script> <div id="loading" ></div> <div id="content" data-page="1"></div> <ul id="pagination"> <?php //Pagination Numbers for($i=1; $i<=$pages; $i++) { echo '<li class="page_numbers" id="page'.$i.'">'.$i.'</li>'; } ?> </ul> <br /> <br /> <a href="#" class="category" id="marketing">Marketing</a> <a href="#" class="category" id="automotive">Automotive</a> <a href="#" class="category" id="sports">Sports</a> Here is the generate pagination where the problem seems to occur: <?php $ids=$_GET['ids']; include_once('config.php'); $per_page = 3; //Calculating no of pages $sql = "SELECT COUNT(*) FROM explore WHERE category='$ids'"; $result = mysql_query($sql); $count = mysql_fetch_row($result); $pages = ceil($count[0]/$per_page); ?> I thought I might as well post the jquery script if someone wants to see: $(document).ready(function(){ //Display Loading Image function Display_Load() { $("#loading").fadeIn(900,0); $("#loading").html("<img src='bigLoader.gif' />"); } //Hide Loading Image function Hide_Load() { $("#loading").fadeOut('slow'); }; //Default Starting Page Results $("#pagination li:first").css({'color' : '#FF0084'}).css({'border' : 'none'}); Display_Load(); $("#content").load("pagination_data.php?page=1", Hide_Load()); // Editing below. // Sort content Marketing $("a.category").click(function() { Display_Load(); var this_id = $(this).attr('id'); $.get("pagination.php", { category: this.id }, function(data){ //Load your results into the page var pageNum = $('#content').attr('data-page'); $("#pagination").load('generate_pagination.php?category=' + pageNum +'&ids='+ this_id ); $("#content").load("filter_marketing.php?page=" + pageNum +'&id='+ this_id, Hide_Load()); }); }); //Pagination Click $("#pagination li").click(function(){ Display_Load(); //CSS Styles $("#pagination li") .css({'border' : 'solid #dddddd 1px'}) .css({'color' : '#0063DC'}); $(this) .css({'color' : '#FF0084'}) .css({'border' : 'none'}); //Loading Data var pageNum = $(this).attr("id").replace("page",""); $("#content").load("pagination_data.php?page=" + pageNum, function(){ $(this).attr('data-page', pageNum); Hide_Load(); }); }); }); If any could assist me on solving this problem that would be great, thanks.

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• Pagination links do not work after first page

  - by TheStack

  Hello, I am trying to fix this pagination script. It seems when I click on the pagination links [1][2][3][4]or[5] , it doesn't work. It just shows the first page and when clicking on the next numbers nothing happens. I hoping someone can see something in the script that I can not see. The main page looks like this (pagination.php): <?php include_once('generate_pagination.php'); ?> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js"></script> <script type="text/javascript" src="jquery_pagination.js"></script> <div id="loading" ></div> <div id="content" data-page="1"></div> <ul id="pagination"> <?php generate_pagination() ?> </ul> <br /> <br /> <a href="#" class="category" id="marketing">Marketing</a> <a href="#" class="category" id="automotive">Automotive</a> <a href="#" class="category" id="sports">Sports</a> Then, generate_pagination.php: <?php function generate_pagination($sql) { include_once('config.php'); $per_page = 3; //Calculating no of pages $result = mysql_query($sql); $count = mysql_fetch_row($result); $pages = ceil($count[0]/$per_page); //Pagination Numbers for($i=1; $i<=$pages; $i++) { echo '<li class="page_numbers" id="'.$i.'">'.$i.'</li>'; } } $ids=$_GET['ids']; generate_pagination("SELECT COUNT(*) FROM explore WHERE category='$ids'"); ?> Here is the jquery file (jquery_pagination.js): $(document).ready(function(){ //Display Loading Image function Display_Load() { $("#loading").fadeIn(900,0); $("#loading").html("<img src='bigLoader.gif' />"); } //Hide Loading Image function Hide_Load() { $("#loading").fadeOut('slow'); }; //Default Starting Page Results $("#pagination li:first").css({'color' : '#FF0084'}).css({'border' : 'none'}); Display_Load(); $("#content").load("pagination_data.php?page=1", Hide_Load()); //Pagination Click $("#pagination li").click(function(){ Display_Load(); //CSS Styles $("#pagination li") .css({'border' : 'solid #dddddd 1px'}) .css({'color' : '#0063DC'}); $(this) .css({'color' : '#FF0084'}) .css({'border' : 'none'}); //Loading Data var pageNum = this.id; $("#content").load("pagination_data.php?page=" + pageNum, function(){ Hide_Load(); $(this).attr('data-page', pageNum); }); }); // Editing below. // Sort content Marketing $("a.category").click(function() { Display_Load(); var this_id = $(this).attr('id'); $.get("pagination.php", { category: this.id }, function(data){ //Load your results into the page var pageNum = $('#content').attr('data-page'); $("#pagination").load('generate_pagination.php?category=' + pageNum +'&ids='+ this_id ); $("#content").load("filter_marketing.php?page=" + pageNum +'&id='+ this_id, Hide_Load()); }); }); }); Lastly, filter_marketing.php (when a user clicks the filter link buttons): <?php include('config.php'); $per_page = 3; if(count($_GET)>0) { if($_GET['page']!=''){ $page=$_GET['page']; } if($_GET['id']!=''){ $id=$_GET['id']; } } $page= ($_GET['page']!='') ? $_GET['page']: false; $id= ($_GET['id']!='') ? $_GET['id']: false; $start = ($page-1)*$per_page; if($page && $id){ $sql = "SELECT * FROM explore WHERE category='$id' ORDER BY category LIMIT $start,$per_page"; } else { die('Error: missing parameters. Id= '.$id.' and page= '.$page); } $result = mysql_query($sql); ?> <table width="800px"> <?php while($row = mysql_fetch_array($result)) { $msg_id=$row['id']; $message=$row['site_description']; $site_price=$row['site_price']; ?> <tr> <td><?php echo $msg_id; ?></td> <td><?php echo $message; ?></td> <td><?php echo $site_price; ?></td> </tr> <?php } ?> </table> So, if anyone sees where the problem is occurring and can help rid of the problem, that would be great, Thank you.

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• .htaccess allow from hostname?

  - by Mikey B

  Ubuntu 9.10 Apache2 Hi Guys, Long story short, I need to restrict access to a certain part of my web site based on a dynamic IP source address that changes every now and then. Historically, I've just added the following to htaccess... order deny,allow deny from all # allow my dynamic IP address allow from <dynamic ip> But the problem is that I'll have to manually make this change every time the IP changes. Ideally I'd like to specify a hostname instead... something like: order deny,allow deny from all # allow my host allow from hostname.whatever.local That doesn't seemed to have worked though. I get an error 403 - access forbidden. Does .htaccess not support hostnames?

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• Safe, standard way to load images in ListView on a different thread?

  - by Po

  Before making this question, I have searched and read these ones: http://stackoverflow.com/questions/541966/android-how-do-i-do-a-lazy-load-of-images-in-listview http://stackoverflow.com/questions/1409623/android-issue-with-lazy-loading-images-into-a-listview My problem is I have a ListView, where: Each row contains an ImageView, whose content is to be loaded from the internet Each row's view is recycled as in ApiDemo's List14 What I want ultimately: Load images lazily, only when the user scrolls to them Load images on different thread(s) to maintain responsiveness My current approach: In the adapter's getView() method, apart from setting up other child views, I launch a new thread that loads the Bitmap from the internet. When that loading thread finishes, it returns the Bitmap to be set on the ImageView (I do this using AsyncTask or Handler). Because I recycle ImageViews, it may be the case that I first want to set a view with Bitmap#1, then later want to set it to Bitmap#2 when the user scrolls down. Bitmap#1 may happen to take longer than Bitmap#2 to load, so it may end up overwriting Bitmap#2 on the view. I solve this by maintaining a WeakHashMap that remembers the last Bitmap I want to set for that view. Below is somewhat a pseudocode for my current approach. I've ommitted other details like caching, just to keep the thing clear. public class ImageLoader { // keeps track of the last Bitmap we want to set for this ImageView private static final WeakHashMap<ImageView, AsyncTask> assignments = new WeakHashMap<ImageView, AsyncTask>(); /** Asynchronously sets an ImageView to some Bitmap loaded from the internet */ public static void setImageAsync(final ImageView imageView, final String imageUrl) { // cancel whatever previous task AsyncTask oldTask = assignments.get(imageView); if (oldTask != null) { oldTask.cancel(true); } // prepare to launch a new task to load this new image AsyncTask<String, Integer, Bitmap> newTask = new AsyncTask<String, Integer, Bitmap>() { protected void onPreExecute() { // set ImageView to some "loading..." image } protected Bitmap doInBackground(String... urls) { return loadFromInternet(imageUrl); } protected void onPostExecute(Bitmap bitmap) { // set Bitmap if successfully loaded, or an "error" image if (bitmap != null) { imageView.setImageBitmap(bitmap); } else { imageView.setImageResource(R.drawable.error); } } }; newTask.execute(); // mark this as the latest Bitmap we want to set for this ImageView assignments.put(imageView, newTask); } /** returns (Bitmap on success | null on error) */ private Bitmap loadFromInternet(String imageUrl) {} } Problem I still have: what if the Activity gets destroyed while some images are still loading? Is there any risk when the loading thread calls back to the ImageView later, when the Activity is already destroyed? Moreover, AsyncTask has some global thread-pool underneath, so if lengthy tasks are not canceled when they're not needed anymore, I may end up wasting time loading things users don't see. My current design of keeping this thing globally is too ugly, and may eventually cause some leaks that are beyond my understanding. Instead of making ImageLoader a singleton like this, I'm thinking of actually creating separate ImageLoader objects for different Activities, then when an Activity gets destroyed, all its AsyncTask will be canceled. Is this too awkward? Anyway, I wonder if there is a safe and standard way of doing this in Android. In addition, I don't know iPhone but is there a similar problem there and do they have a standard way to do this kind of task? Many thanks.

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• Windows boots to Black Screen of Death — Is my HDD faulty?

  - by Flynn1179

  My wife's PC suddenly stopped booting up properly. It gets as far as the Windows 'loading' screen with the bar scrolling away, but that's as far as it gets for some time, then suddenly flashes up a BSoD barely long enough to see, then the display cuts out. We've got identical PCs, and after swapping components, I established that my PC suffers the same problem if I swap in the HDD. Even if I plug hers in as a second HDD on my machine, it still does the same thing, even though it's booting from mine. I can't even boot her machine from CD or DVD either, so I couldn't even use a recovery disc. I did manage to partially boot my PC into safe mode with the other HDD attached, and it got as far as loading 'crcdisk.sys' and froze. Anybody know what could be wrong with it, or at least how I can get the data off the disk? I'm assuming there's still data on the disk, given that it at least shows me the vista 'loading' screen.

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• Windows 2003 DNS updates from ISC DHCP server

  - by wolfgangsz

  We have a very mixed network, with most clients being Debian Lenny, the rest Windows XP/Vista/7. The network itself is split into two segments (for technical reasons) called "corporate" and "engineering". On the "corporate" side all clients get their IP addresses from a Windows DHCP server and the dynamic updates into the Windows DNS work just fine. On the "engineering" side, clients get their IP addresses from a linux machine running the standard ISC DHCP server. Although this server is configured to do dynamic DNS updates, they actually don't work. Anybody got any advice on how to fix this? Please note: dynamic updates from the clients directly into the DNS would work, but are not an option for us. So this is strictly on how make this work from an ISC DHCP server to a Windows DNS server.

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• Relay thru external SMTP server on Exchange 2010

  - by MadBoy

  My client has dynamic IP on which he hosts Exchange 2010 with POP3 Connector running and gathering emails from his current hosting. Until he gets static IP he wants to send emails out. This will work most of the time but some servers won't accept such email sent by Exchange (from dynamic ip due to multiple reasons) so I would like to make a relay thru external SMTP server which hosts current mailboxes. Normally SMTP server could be set up to allow relay thru it but this would require static IP to be allowed on that server so it would know which IP is allowed to relay thru it. Or is there a way to setup relay in Exchange 2010 so it can use dynamic IP and kinda authenticates with user/password itself on the hosted server?

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• Computer still in boot loop

  - by user2856410

  My computer is in a boot loop and despite all my efforts, I haven't been able to load windows XP with it. When the computer loads, I see some white loading bar at the bottom, then the windows XP loading screen, then the DELL boot screen, then windows XP loading screen, and it just keeps looping. The blue screen error is: UNMOUNTABLE_BOOT_VOLUME Stop: 0x000000ED (0x823D6C08, 0xC000009C, 0x000000000, 0x000000000) I have booted using Hiren's mini XP, and ran CHKDSK /f /r, but it didn't affect the boot loop. Is there anything else I can try to get my computer to start up? I don't have my windows XP disc, but I have a dvd burner on another computer, and can burn a downloaded ISO if it could help me get out of this loop. Thanks!

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• Why can't I play YouTube clips properly anymore?

  - by NoCanDo

  I haven't got the faintest idea what happened, but since about 3-4 days now I can't play any clips on YouTube properly at all. Proper as in continuously without loading, pause, playback, pause, loading, playback, pause, loading, playback, etc. I haven't changed anything hardware nor software-wise. On the other hand I can play Break.com, Viddler, Liveleak, Metacafe without any trouble. I tried my own tips, but that hasn't helped me at all. What on earth happend? Is it me, or is it YouTube? I'm using Firefox 3.6 Beta 5. But the issue is the same on Chrome as well as on Internet Explorer.

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• Assign two static IP addresses to one mac address

  - by Timo Ylikännö

  Can Isc-dhcp-server give two static ip addresses to one mac address? I have several home terminals in my network. Each terminal have two interfaces. One for public traffic and one for a management traffic. Both interfaces have same mac address. DHCP server can detect interfaces via dhcp option field and dhcp class declarations. Every terminal have to have static ip address instead of dynamic address. With dynamic address and dynamic pools this would be an easy task. Or is there any dhcp server that can do this?

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• Google Chrome Automatic Page Load

  - by WDC

  Google Chrome keeps loading the second page of certain websites which is helpful on sites like Netflix so that instead of clicking on a link for page 2, I can just continue scrolling down and it'll automatically have the next page ready for me. But on online clothing sites, it just gets backed up loading all the next pages, misplacing links and loading the next page so that it actually replaces the page I'm trying to view literally every millisecond. Considering clothing sites generally have upwards of 20 to 200 pages of clothing, this is really annoying since Chrome tries to load all of them. How do I turn off the automatic page load???

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• g++ symbol versioning. Set it to GCC_3.0 using version 4 of g++

  - by Ismael

  Hi all I need to implemente a Java class which uses JNI to control a fiscal printer in XUbuntu 8.10 with sun-java6-jdk installed. The structure is the following: EpsonDriver.java loads libEpson.so libEpson is linked dynamically with EpsonFiscalProtocol.so ( provided by Epson, no source available ) and pthread I use javah to generate the header file, and the code compiles. Then I put the libEpson.so in $JAVA_HOME/jre/lib/i386, and EpsonDriver.java uses an static initializar System.loadLibrary("libEpson") That part works, however, when I try to use any of the methods I get an unsatisfiedLinkError exception. Some time ago, a coworker did a version that works, and using objdump -Dslx I got the following: Program Header: LOAD off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**12 filesz 0x0000ccc4 memsz 0x0000ccc4 flags r-x LOAD off 0x0000d000 vaddr 0x0000d000 paddr 0x0000d000 align 2**12 filesz 0x00000250 memsz 0x00044a5c flags rw- DYNAMIC off 0x0000d014 vaddr 0x0000d014 paddr 0x0000d014 align 2**2 filesz 0x000000f0 memsz 0x000000f0 flags rw- NOTE off 0x000000d4 vaddr 0x000000d4 paddr 0x000000d4 align 2**2 filesz 0x00000024 memsz 0x00000024 flags r-- STACK off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2 filesz 0x00000000 memsz 0x00000000 flags rw- Dynamic Section: NEEDED EpsonFiscalProtocol.so NEEDED libpthread.so.0 NEEDED libstdc++.so.6 NEEDED libm.so.6 NEEDED libc.so.6 SONAME libcom_tichile_jpos_EpsonSerialDriver.so INIT 0x00007254 FINI 0x0000ba08 GNU_HASH 0x000000f8 STRTAB 0x00001f50 SYMTAB 0x00000ae0 STRSZ 0x00002384 SYMENT 0x00000010 PLTGOT 0x0000d108 PLTRELSZ 0x00000008 PLTREL 0x00000011 JMPREL 0x0000724c REL 0x000045c4 RELSZ 0x00002c88 RELENT 0x00000008 TEXTREL 0x00000000 VERNEED 0x00004564 VERNEEDNUM 0x00000002 VERSYM 0x000042d4 RELCOUNT 0x000000ac Version References: required from libstdc++.so.6: 0x056bafd3 0x00 05 CXXABI_1.3 0x08922974 0x00 04 GLIBCXX_3.4 required from libc.so.6: 0x0b792650 0x00 03 GCC_3.0 0x0d696910 0x00 02 GLIBC_2.0 In the recently compiled file I get: Program Header: LOAD off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**12 filesz 0x00005300 memsz 0x00005300 flags r-x LOAD off 0x00005300 vaddr 0x00006300 paddr 0x00006300 align 2**12 filesz 0x00000274 memsz 0x00010314 flags rw- DYNAMIC off 0x00005314 vaddr 0x00006314 paddr 0x00006314 align 2**2 filesz 0x000000e0 memsz 0x000000e0 flags rw- EH_FRAME off 0x00004a00 vaddr 0x00004a00 paddr 0x00004a00 align 2**2 filesz 0x00000154 memsz 0x00000154 flags r-- Dynamic Section: NEEDED libstdc++.so.5 NEEDED libm.so.6 NEEDED libgcc_s.so.1 NEEDED libc.so.6 SONAME EpsonFiscalProtocol.so INIT 0x00001cb4 FINI 0x00004994 HASH 0x000000b4 STRTAB 0x00000da4 SYMTAB 0x000004f4 STRSZ 0x00000acf SYMENT 0x00000010 PLTGOT 0x0000640c PLTRELSZ 0x00000270 PLTREL 0x00000011 JMPREL 0x00001a44 REL 0x000019dc RELSZ 0x00000068 RELENT 0x00000008 VERNEED 0x0000198c VERNEEDNUM 0x00000002 VERSYM 0x00001874 RELCOUNT 0x00000004 Version References: required from libstdc++.so.5: 0x056bafd2 0x00 04 CXXABI_1.2 required from libc.so.6: 0x09691f73 0x00 03 GLIBC_2.1.3 0x0d696910 0x00 02 GLIBC_2.0 So I suspect the main diference is the GCC_3.0 symbol I compile libcom_tichile_EpsonSerialDriver.so with the following command ( from memory as I not at work right now ) g++ -Wl,-soname=.... -shared -I/*jni libraries*/ -o libcom_tichile_jpos_EpsonSerialDriver -lEpsonFiscalProtocol -lpthread Is there any way to tell g++ to use that symbol version? Or any idea in how to make it work? EDIT: I have another non-working version with the followin dump: Program Header: LOAD off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**12 filesz 0x0000bf68 memsz 0x0000bf68 flags r-x LOAD off 0x0000cc0c vaddr 0x0000cc0c paddr 0x0000cc0c align 2**12 filesz 0x000005e8 memsz 0x00044df0 flags rw- DYNAMIC off 0x0000cc20 vaddr 0x0000cc20 paddr 0x0000cc20 align 2**2 filesz 0x000000f8 memsz 0x000000f8 flags rw- EH_FRAME off 0x0000b310 vaddr 0x0000b310 paddr 0x0000b310 align 2**2 filesz 0x000002bc memsz 0x000002bc flags r-- STACK off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2 filesz 0x00000000 memsz 0x00000000 flags rw- RELRO off 0x0000cc0c vaddr 0x0000cc0c paddr 0x0000cc0c align 2**0 filesz 0x000003f4 memsz 0x000003f4 flags r-- Dynamic Section: NEEDED EpsonFiscalProtocol.so NEEDED libpthread.so.0 NEEDED libstdc++.so.6 NEEDED libm.so.6 NEEDED libgcc_s.so.1 NEEDED libc.so.6 SONAME libcom_tichile_jpos_EpsonSerialDriver.so INIT 0x000055d8 FINI 0x0000a968 HASH 0x000000f4 GNU_HASH 0x00000a30 STRTAB 0x00002870 SYMTAB 0x00001410 STRSZ 0x00002339 SYMENT 0x00000010 PLTGOT 0x0000cff4 PLTRELSZ 0x00000168 PLTREL 0x00000011 JMPREL 0x00005470 REL 0x00004ea8 RELSZ 0x000005c8 RELENT 0x00000008 VERNEED 0x00004e38 VERNEEDNUM 0x00000002 VERSYM 0x00004baa RELCOUNT 0x00000001 Version References: required from libstdc++.so.6: 0x056bafd3 0x00 05 CXXABI_1.3 0x08922974 0x00 03 GLIBCXX_3.4 required from libc.so.6: 0x09691f73 0x00 06 GLIBC_2.1.3 0x0d696914 0x00 04 GLIBC_2.4 0x0d696910 0x00 02 GLIBC_2.0 Now I think the main difference is in the GCC_3.0 symbol/ABI EDIT: Luckily, a coworker found a way to talk to the printer using Java

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• How to increase signal/range of your Wi-Fi antenna-less repeater/booster over the network?

  - by kenorb

  I've BT Home Hub in the upper flat (2-3 walls behind) and I'm using WPS Wireless-N Wifi Range Router Repeater Extender in my flat where I'm using my laptop. These are antenna-less devices. Are there any life-hack tricks to increase signal/range of my repeater without buying the new more powerful repeater? I've tried already to move my repeater closer to the ceiling or putting the aluminium foil underneath, but it didn't help. Are there any methods, specific plates or materials which can boost the signal? Specification: Model: WN518W2 Frequency range: 2.4-2.4835GHz Wireless transmit power: 14 ~17 dBm (Typical) Wireless Signal Rates With Automatic Fallback: 11n: Up to 300Mbps(dynamic), 11g: Up to 54Mbps(dynamic), 11b: Up to 11Mbps(dynamic) Modulation Technology: DBPSK, DQPSK, CCK, OFDM, 16-QAM, 64-QAM Receiver Sensitivity: 300M: -68dBm@10% PER / 150M: -68dBm@10% PER / 108M: -68dBm@10% PER / 54M: -68dBm@10% PER / 11M: -85dBm@8% PER / 6M: -88dBm@10% PER / 1M: -90dBm@8% PER Product dimensions: 11 * 6 * 7cm

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• Troubleshooting web page load issues

  - by Richard Testani

  I having an odd issue where a particular page doesn't finish loading... all the time. Intermittenly, this page doesn't finish loading - in particluar, it seems maybe the JS file isn't downloaded or finished loading. Marchelos Law I am not sure how to troubleshoot this issue, since refreshing it fixes it. I see it mostly in IE 7 & 8, rarely in Safari or FireFox. If you view the page in question, refreshing it - you should see the issue. Any ideas?

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• forward all ports via htaccess to new address

  - by user875933

  I have a chat server running on my local machine that listens to different ports. I want to use the sub-domain of one of my accounts to access it. I intend to manually change the redirect whenever my local machine gets a different ip address. So: chat.example.com:123 would redirect to dynamic.ip.address:123 I am trying to accomplish this with .htaccess and RewriteRule I have tried: RewriteEngine on RewriteRule ^(.*) http://dynamic.ip.address/ [L, R=302] but this doesn't work. When I try chat.example.com:123 nothing happens. When I input chat.example.com into the web browser, I get dynamic.ip.address Is .htaccess the right tool for this? I am using a simple web host that gives me ssh access, but not much more.

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• Bootcamp: setup of Windows 7 (64 bit) hanging at "disk.sys"

  - by Skade

  I am having trouble getting Windows 7 Professional (64bit) to install on a Macbook Pro (late 2010 model). The installer hangs when loading the setup from disk. When restarting, I get an option to boot Windows from disk. The installer then starts loading files from disk and suddenly hangs. Using "Safe Mode" (from the advanced menu), it tells me that the installer hangs when loading "disk.sys". The installation is made on a fresh Bootcamp partition, the disk uses GPT. Has anyone seen this before and maybe found a solution?

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• Permissions problem running Apache ActiveMQ

  - by Edd

  I'm wanting to use Apache ActiveMQ on Ubuntu 12.04 LTS, but am running into what looks like a permissions problem when I try to run it as follows: edd:~$ sudo activemq --version INFO: Loading '/usr/share/activemq/activemq-options' INFO: Using java '/usr/lib/jvm/java-6-openjdk//bin/java' INFO: changing to user 'activemq' to invoke java Java Runtime: Sun Microsystems Inc. 1.6.0_24 /usr/lib/jvm/java-6-openjdk-amd64/jre Heap sizes: current=502464k free=499842k max=502464k JVM args: -Xms512M -Xmx512M -Dorg.apache.activemq.UseDedicatedTaskRunner=true -Dactivemq.classpath=/var/lib/activemq//conf;; -Dactivemq.home=/usr/share/activemq -Dactivemq.base=/var/lib/activemq/ ACTIVEMQ_HOME: /usr/share/activemq ACTIVEMQ_BASE: /var/lib/activemq ActiveMQ 5.5.0 For help or more information please see: http://activemq.apache.org edd:~$ sudo activemq start INFO: Loading '/usr/share/activemq/activemq-options' INFO: Using java '/usr/lib/jvm/java-6-openjdk//bin/java' INFO: Starting - inspect logfiles specified in logging.properties and log4j.properties to get details INFO: changing to user 'activemq' to invoke java -su: line 2: /var/run/activemq.pid: Permission denied INFO: pidfile created : '/var/run/activemq.pid' (pid '7811') edd:~$ sudo activemq status INFO: Loading '/usr/share/activemq/activemq-options' INFO: Using java '/usr/lib/jvm/java-6-openjdk//bin/java' ActiveMQ not running edd:~$ ps ax | grep 'activemq' 8040 pts/0 S+ 0:00 grep --color=auto activemq I installed ActiveMQ using sudo apt-get install activemq. Apologies if there's any additional information missing - I'm fairly new to Linux as you may well have guessed!

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• Back to Basics: When does a .NET Assembly Dependency get loaded

  - by Rick Strahl

  When we work on typical day to day applications, it's easy to forget some of the core features of the .NET framework. For me personally it's been a long time since I've learned about some of the underlying CLR system level services even though I rely on them on a daily basis. I often think only about high level application constructs and/or high level framework functionality, but the low level stuff is often just taken for granted. Over the last week at DevConnections I had all sorts of low level discussions with other developers about the inner workings of this or that technology (especially in light of my Low Level ASP.NET Architecture talk and the Razor Hosting talk). One topic that came up a couple of times and ended up a point of confusion even amongst some seasoned developers (including some folks from Microsoft <snicker>) is when assemblies actually load into a .NET process. There are a number of different ways that assemblies are loaded in .NET. When you create a typical project assemblies usually come from: The Assembly reference list of the top level 'executable' project The Assembly references of referenced projects Dynamically loaded at runtime via AppDomain/Reflection loading In addition .NET automatically loads mscorlib (most of the System namespace) the boot process that hosts the .NET runtime in EXE apps, or some other kind of runtime hosting environment (runtime hosting in servers like IIS, SQL Server or COM Interop). In hosting environments the runtime host may also pre-load a bunch of assemblies on its own (for example the ASP.NET host requires all sorts of assemblies just to run itself, before ever routing into your user specific code). Assembly Loading The most obvious source of loaded assemblies is the top level application's assembly reference list. You can add assembly references to a top level application and those assembly references are then available to the application. In a nutshell, referenced assemblies are not immediately loaded - they are loaded on the fly as needed. So regardless of whether you have an assembly reference in a top level project, or a dependent assembly assemblies typically load on an as needed basis, unless explicitly loaded by user code. The same is true of dependent assemblies. To check this out I ran a simple test: I have a utility assembly Westwind.Utilities which is a general purpose library that can work in any type of project. Due to a couple of small requirements for encoding and a logging piece that allows logging Web content (dependency on HttpContext.Current) this utility library has a dependency on System.Web. Now System.Web is a pretty large assembly and generally you'd want to avoid adding it to a non-Web project if it can be helped. So I created a Console Application that loads my utility library: You can see that the top level Console app a reference to Westwind.Utilities and System.Data (beyond the core .NET libs). The Westwind.Utilities project on the other hand has quite a few dependencies including System.Web. I then add a main program that accesses only a simple utillity method in the Westwind.Utilities library that doesn't require any of the classes that access System.Web: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.ReadLine(); } StringUtils.NewStringId() calls into Westwind.Utilities, but it doesn't rely on System.Web. Any guesses what the assembly list looks like when I stop the code on the ReadLine() command? I'll wait here while you think about it… … … So, when I stop on ReadLine() and then fire up Process Explorer and check the assembly list I get: We can see here that .NET has not actually loaded any of the dependencies of the Westwind.Utilities assembly. Also not loaded is the top level System.Data reference even though it's in the dependent assembly list of the top level project. Since this particular function I called only uses core System functionality (contained in mscorlib) there's in fact nothing else loaded beyond the main application and my Westwind.Utilities assembly that contains the method accessed. None of the dependencies of Westwind.Utilities loaded. If you were to open the assembly in a disassembler like Reflector or ILSpy, you would however see all the compiled in dependencies. The referenced assemblies are in the dependency list and they are loadable, but they are not immediately loaded by the application. In other words the C# compiler and .NET linker are smart enough to figure out the dependencies based on the code that actually is referenced from your application and any dependencies cascading down into the dependencies from your top level application into the referenced assemblies. In the example above the usage requirement is pretty obvious since I'm only calling a single static method and then exiting the app, but in more complex applications these dependency relationships become very complicated - however it's all taken care of by the compiler and linker figuring out what types and members are actually referenced and including only those assemblies that are in fact referenced in your code or required by any of your dependencies. The good news here is: That if you are referencing an assembly that has a dependency on something like System.Web in a few places that are not actually accessed by any of your code or any dependent assembly code that you are calling, that assembly is never loaded into memory! Some Hosting Environments pre-load Assemblies The load behavior can vary however. In Console and desktop applications we have full control over assembly loading so we see the core CLR behavior. However other environments like ASP.NET for example will preload referenced assemblies explicitly as part of the startup process - primarily to minimize load conflicts. Specifically ASP.NET pre-loads all assemblies referenced in the assembly list and the /bin folder. So in Web applications it definitely pays to minimize your top level assemblies if they are not used. Understanding when Assemblies Load To clarify and see it actually happen what I described in the first example , let's look at a couple of other scenarios. To see assemblies loading at runtime in real time lets create a utility function to print out loaded assemblies to the console: public static void PrintAssemblies() { var assemblies = AppDomain.CurrentDomain.GetAssemblies(); foreach (var assembly in assemblies) { Console.WriteLine(assembly.GetName()); } } Now let's look at the first scenario where I have class method that references internally uses System.Web. In the first scenario lets add a method to my main program like this: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.ReadLine(); PrintAssemblies(); } public static void WebLogEntry() { var entry = new WebLogEntry(); entry.UpdateFromRequest(); Console.WriteLine(entry.QueryString); } UpdateFromWebRequest() internally accesses HttpContext.Current to read some information of the ASP.NET Request object so it clearly needs a reference System.Web to work. In this first example, the method that holds the calling code is never called, but exists as a static method that can potentially be called externally at some point. What do you think will happen here with the assembly loading? Will System.Web load in this example? No - it doesn't. Because the WebLogEntry() method is never called by the mainline application (or anywhere else) System.Web is not loaded. .NET dynamically loads assemblies as code that needs it is called. No code references the WebLogEntry() method and so System.Web is never loaded. Next, let's add the call to this method, which should trigger System.Web to be loaded because a dependency exists. Let's change the code to: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.WriteLine("--- Before:"); PrintAssemblies(); WebLogEntry(); Console.WriteLine("--- After:"); PrintAssemblies(); Console.ReadLine(); } public static void WebLogEntry() { var entry = new WebLogEntry(); entry.UpdateFromRequest(); Console.WriteLine(entry.QueryString); } Looking at the code now, when do you think System.Web will be loaded? Will the before list include it? Yup System.Web gets loaded, but only after it's actually referenced. In fact, just until before the call to UpdateFromRequest() System.Web is not loaded - it only loads when the method is actually called and requires the reference in the executing code. Moral of the Story So what have we learned - or maybe remembered again? Dependent Assembly References are not pre-loaded when an application starts (by default) Dependent Assemblies that are not referenced by executing code are never loaded Dependent Assemblies are just in time loaded when first referenced in code All of this is nothing new - .NET has always worked like this. But it's good to have a refresher now and then and go through the exercise of seeing it work in action. It's not one of those things we think about everyday, and as I found out last week, I couldn't remember exactly how it worked since it's been so long since I've learned about this. And apparently I'm not the only one as several other people I had discussions with in relation to loaded assemblies also didn't recall exactly what should happen or assumed incorrectly that just having a reference automatically loads the assembly. The moral of the story for me is: Trying at all costs to eliminate an assembly reference from a component is not quite as important as it's often made out to be. For example, the Westwind.Utilities module described above has a logging component, including a Web specific logging entry that supports pulling information from the active HTTP Context. Adding that feature requires a reference to System.Web. Should I worry about this in the scope of this library? Probably not, because if I don't use that one class of nearly a hundred, System.Web never gets pulled into the parent process. IOW, System.Web only loads when I use that specific feature and if I am, well I clearly have to be running in a Web environment anyway to use it realistically. The alternative would be considerably uglier: Pulling out the WebLogEntry class and sticking it into another assembly and breaking up the logging code. In this case - definitely not worth it. So, .NET definitely goes through some pretty nifty optimizations to ensure that it loads only what it needs and in most cases you can just rely on .NET to do the right thing. Sometimes though assembly loading can go wrong (especially when signed and versioned local assemblies are involved), but that's subject for a whole other post…© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  CSharp   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Can't add Fedora 14 to grub.

  - by Dananjaya

  Today I installed Fedora 14 in a different partition in the same hard drive as Ubuntu. At the Fedora 14 installation, I chose not to install Boot-loader in the MBR, and instead chose to install it in the Fedora partition itself, which is according to my HD layout /sda3. After the Fedora 14 installation I booted in to Ubuntu and ran sudo update-grub but 'grub.cfg' fails to add Fedora 14 in to the OS list. Here is the output of boot-info script. Boot Info Script 0.60 from 17 May 2011 ============================= Boot Info Summary: =============================== = Grub2 (v1.99) is installed in the MBR of /dev/sda and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks for (,msdos1)/boot/grub on this drive. sda1: __________________________________________________________________________ File system: ext4 Boot sector type: - Boot sector info: Operating System: Ubuntu 11.04 Boot files: /boot/grub/grub.cfg /etc/fstab /boot/grub/core.img sda2: __________________________________________________________________________ File system: Extended Partition Boot sector type: Unknown Boot sector info: sda5: __________________________________________________________________________ File system: swap Boot sector type: - Boot sector info: sda3: __________________________________________________________________________ File system: ext4 Boot sector type: Grub Legacy Boot sector info: Grub Legacy (v0.97) is installed in the boot sector of sda3 and looks at sector 49897340 on boot drive #1 for the stage2 file. A stage2 file is at this location on /dev/sda. Stage2 looks on partition #3 for /grub/grub.conf. Operating System: Boot files: /grub/menu.lst /grub/grub.conf sda4: __________________________________________________________________________ File system: LVM2_member Boot sector type: - Boot sector info: ============================ Drive/Partition Info: ============================= Drive: sda _____________________________________________________________________ Disk /dev/sda: 40.0 GB, 40020664320 bytes 255 heads, 63 sectors/track, 4865 cylinders, total 78165360 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes Partition Boot Start Sector End Sector # of Sectors Id System /dev/sda1 * 2,048 49,865,759 49,863,712 83 Linux /dev/sda2 74,866,686 78,163,967 3,297,282 5 Extended /dev/sda5 74,866,688 78,163,967 3,297,280 82 Linux swap / Solaris /dev/sda3 49,866,752 50,890,751 1,024,000 83 Linux /dev/sda4 50,890,752 74,864,639 23,973,888 8e Linux LVM "blkid" output: ________________________________________________________________ Device UUID TYPE LABEL /dev/sda1 03e2a8da-171f-49e9-b24d-434e66cd1140 ext4 /dev/sda3 dea81d77-a375-4d0e-954e-1829f6b91f10 ext4 /dev/sda4 mzVoj0-GHJu-DJr4-0G2Y-SzZ0-LTfW-F01yf9 LVM2_member /dev/sda5 3e89ba8e-7754-4ee4-aca1-e2a82bffb7a7 swap ================================ Mount points: ================================= Device Mount_Point Type Options /dev/sda1 / ext4 (rw,errors=remount-ro,user_xattr,commit=0) =========================== sda1/boot/grub/grub.cfg: =========================== -------------------------------------------------------------------------------- # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="2" if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { insmod vbe insmod vga insmod video_bochs insmod video_cirrus } insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 if loadfont /usr/share/grub/unicode.pf2 ; then set gfxmode=1024x768 load_video insmod gfxterm fi terminal_output gfxterm insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 set locale_dir=($root)/boot/grub/locale set lang=en_US insmod gettext if [ "${recordfail}" = 1 ]; then set timeout=-1 else set timeout=10 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 44,0,30; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### if [ ${recordfail} != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode if [ "$linux_gfx_mode" != "text" ]; then load_video; fi menuentry 'Ubuntu, with Linux 2.6.38-8-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail set gfxpayload=$linux_gfx_mode insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 linux /boot/vmlinuz-2.6.38-8-generic root=UUID=03e2a8da-171f-49e9-b24d-434e66cd1140 ro quiet splash vt.handoff=7 initrd /boot/initrd.img-2.6.38-8-generic } menuentry 'Ubuntu, with Linux 2.6.38-8-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail set gfxpayload=$linux_gfx_mode insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 echo 'Loading Linux 2.6.38-8-generic ...' linux /boot/vmlinuz-2.6.38-8-generic root=UUID=03e2a8da-171f-49e9-b24d-434e66cd1140 ro single echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-2.6.38-8-generic } submenu "Previous Linux versions" { menuentry 'Ubuntu, with Linux 2.6.35-28-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail set gfxpayload=$linux_gfx_mode insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 linux /boot/vmlinuz-2.6.35-28-generic root=UUID=03e2a8da-171f-49e9-b24d-434e66cd1140 ro quiet splash vt.handoff=7 initrd /boot/initrd.img-2.6.35-28-generic } menuentry 'Ubuntu, with Linux 2.6.35-28-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail set gfxpayload=$linux_gfx_mode insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 echo 'Loading Linux 2.6.35-28-generic ...' linux /boot/vmlinuz-2.6.35-28-generic root=UUID=03e2a8da-171f-49e9-b24d-434e66cd1140 ro single echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-2.6.35-28-generic } menuentry 'Ubuntu, with Linux 2.6.32-21-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail set gfxpayload=$linux_gfx_mode insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 linux /boot/vmlinuz-2.6.32-21-generic root=UUID=03e2a8da-171f-49e9-b24d-434e66cd1140 ro quiet splash vt.handoff=7 initrd /boot/initrd.img-2.6.32-21-generic } menuentry 'Ubuntu, with Linux 2.6.32-21-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail set gfxpayload=$linux_gfx_mode insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 echo 'Loading Linux 2.6.32-21-generic ...' linux /boot/vmlinuz-2.6.32-21-generic root=UUID=03e2a8da-171f-49e9-b24d-434e66cd1140 ro single echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-2.6.32-21-generic } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod part_msdos insmod ext2 set root='(/dev/sda,msdos1)' search --no-floppy --fs-uuid --set=root 03e2a8da-171f-49e9-b24d-434e66cd1140 linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### if [ "x${timeout}" != "x-1" ]; then if keystatus; then if keystatus --shift; then set timeout=-1 else set timeout=0 fi else if sleep --interruptible 3 ; then set timeout=0 fi fi fi ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### -------------------------------------------------------------------------------- =============================== sda1/etc/fstab: ================================ -------------------------------------------------------------------------------- # /etc/fstab: static file system information. # # Use 'blkid -o value -s UUID' to print the universally unique identifier # for a device; this may be used with UUID= as a more robust way to name # devices that works even if disks are added and removed. See fstab(5). # # proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/sda1 during installation # Commented out by Dropbox # UUID=03e2a8da-171f-49e9-b24d-434e66cd1140 / ext4 errors=remount-ro 0 1 # swap was on /dev/sda5 during installation UUID=3e89ba8e-7754-4ee4-aca1-e2a82bffb7a7 none swap sw 0 0 UUID=03e2a8da-171f-49e9-b24d-434e66cd1140 / ext4 errors=remount-ro,user_xattr 0 1 -------------------------------------------------------------------------------- =================== sda1: Location of files loaded by Grub: ==================== GiB - GB File Fragment(s) 0.065803528 = 0.070656000 boot/grub/core.img 1 21.263332367 = 22.831329280 boot/grub/grub.cfg 1 0.771381378 = 0.828264448 boot/initrd.img-2.6.31-wl 1 2.054199219 = 2.205679616 boot/initrd.img-2.6.32-21-generic 3 2.893260956 = 3.106615296 boot/initrd.img-2.6.35-28-generic 2 6.833232880 = 7.337127936 boot/initrd.img-2.6.38-8-generic 2 1.772453308 = 1.903157248 boot/vmlinuz-2.6.32-21-generic 2 2.068012238 = 2.220511232 boot/vmlinuz-2.6.35-28-generic 1 5.532531738 = 5.940510720 boot/vmlinuz-2.6.38-8-generic 1 6.833232880 = 7.337127936 initrd.img 2 2.893260956 = 3.106615296 initrd.img.old 2 5.532531738 = 5.940510720 vmlinuz 1 2.068012238 = 2.220511232 vmlinuz.old 1 ============================= sda3/grub/grub.conf: ============================= -------------------------------------------------------------------------------- # grub.conf generated by anaconda # # Note that you do not have to rerun grub after making changes to this file # NOTICE: You have a /boot partition. This means that # all kernel and initrd paths are relative to /boot/, eg. # root (hd0,2) # kernel /vmlinuz-version ro root=/dev/mapper/VolGroup-lv_root # initrd /initrd-[generic-]version.img #boot=/dev/sda3 default=0 timeout=0 splashimage=(hd0,2)/grub/splash.xpm.gz hiddenmenu title Fedora (2.6.35.6-45.fc14.i686) root (hd0,2) kernel /vmlinuz-2.6.35.6-45.fc14.i686 ro root=/dev/mapper/VolGroup-lv_root rd_LVM_LV=VolGroup/lv_root rd_LVM_LV=VolGroup/lv_swap rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet initrd /initramfs-2.6.35.6-45.fc14.i686.img -------------------------------------------------------------------------------- =================== sda3: Location of files loaded by Grub: ==================== GiB - GB File Fragment(s) 23.792903900 = 25.547436032 grub/grub.conf 1 23.792903900 = 25.547436032 grub/menu.lst 1 23.793020248 = 25.547560960 grub/stage2 1 23.817364693 = 25.573700608 initramfs-2.6.35.6-45.fc14.i686.img 2 23.787566185 = 25.541704704 initrd-plymouth.img 1 23.791228294 = 25.545636864 vmlinuz-2.6.35.6-45.fc14.i686 1 ======================== Unknown MBRs/Boot Sectors/etc: ======================== Unknown BootLoader on sda2 00000000 81 71 62 ff a1 94 89 ff 4d 43 3a ff fa f2 ec ff |.qb.....MC:.....| 00000010 fb f6 f1 ff fc f8 f4 ff fc f8 f4 ff fc f8 f4 ff |................| 00000020 5d 56 50 ff a1 94 89 ff 81 70 62 ff 81 70 62 ff |]VP......pb..pb.| 00000030 81 70 62 ff 81 70 62 ff 81 70 62 ff a1 94 89 ff |.pb..pb..pb.....| 00000040 4d 43 3a ff fa f2 ec ff fb f6 f1 ff fc f8 f4 ff |MC:.............| 00000050 fc f8 f4 ff fc f8 f4 ff 5d 56 50 ff a1 94 89 ff |........]VP.....| 00000060 81 70 62 ff 81 70 62 ff 81 70 62 ff 81 70 62 ff |.pb..pb..pb..pb.| 00000070 81 70 62 ff a1 94 89 ff 4d 43 3a ff fa f2 ec ff |.pb.....MC:.....| 00000080 fb f6 f1 ff fc f8 f4 ff fc f8 f4 ff fc f8 f4 ff |................| 00000090 5d 56 50 ff a0 93 89 ff 80 6f 61 ff 80 6f 61 ff |]VP......oa..oa.| 000000a0 80 6f 61 ff 80 6f 61 ff 80 6f 61 ff a0 93 89 ff |.oa..oa..oa.....| 000000b0 4d 43 3a ff fa f2 ed ff fb f6 f2 ff fc f8 f5 ff |MC:.............| 000000c0 fc f8 f5 ff fc f8 f5 ff 5d 56 50 ff 9f 93 88 ff |........]VP.....| 000000d0 7f 6f 60 ff 7f 6f 60 ff 7f 6f 60 ff 7f 6f 60 ff |.o`..o`..o`..o`.| 000000e0 7f 6f 60 ff 9f 93 88 ff 4d 43 3a ff fa f2 ed ff |.o`.....MC:.....| 000000f0 fb f6 f2 ff fc f8 f5 ff fc f8 f5 ff fc f8 f5 ff |................| 00000100 5d 56 50 ff 9f 93 88 ff 7f 6f 60 ff 7f 6f 60 ff |]VP......o`..o`.| 00000110 7f 6f 60 ff 7f 6f 60 ff 7f 6f 60 ff 9f 93 88 ff |.o`..o`..o`.....| 00000120 4d 43 3a ff fa f2 ed ff fb f6 f2 ff fc f8 f5 ff |MC:.............| 00000130 fc f8 f5 ff fc f8 f5 ff 5d 56 50 ff 9e 92 88 ff |........]VP.....| 00000140 7e 6e 60 ff 7e 6e 60 ff 7e 6e 60 ff 7e 6e 60 ff |~n`.~n`.~n`.~n`.| 00000150 7e 6e 60 ff 9e 92 88 ff 4d 43 3a ff fa f2 ed ff |~n`.....MC:.....| 00000160 fb f6 f2 ff fc f8 f5 ff fc f8 f5 ff fc f8 f5 ff |................| 00000170 5d 56 50 ff 9e 92 88 ff 7d 6d 5f ff 7d 6d 5f ff |]VP.....}m_.}m_.| 00000180 7d 6d 5f ff 7d 6d 5f ff 7d 6d 5f ff 9e 92 88 ff |}m_.}m_.}m_.....| 00000190 4d 43 3a ff fa f2 ed ff fb f6 f2 ff fc f8 f5 ff |MC:.............| 000001a0 fc f8 f5 ff fc f8 f5 ff 5d 56 50 ff 9e 92 88 ff |........]VP.....| 000001b0 7d 6d 5f ff 7d 6d 5f ff 7d 6d 5f ff 7d 6d 00 fe |}m_.}m_.}m_.}m..| 000001c0 ff ff 82 fe ff ff 02 00 00 00 00 50 32 00 00 00 |...........P2...| 000001d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.| 00000200 =============================== StdErr Messages: =============================== unlzma: Decoder error According to this Fedora 14 is visible in sda3. Does anybody know a way to add Fedora 14 to grub.cfg of Ubuntu so I can choose which OS to boot? Thanks in advance.

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• Announcing ASP.NET MVC 3 (Release Candidate 2)

  - by ScottGu

  Earlier today the ASP.NET team shipped the final release candidate (RC2) for ASP.NET MVC 3.  You can download and install it here. Almost there… Today’s RC2 release is the near-final release of ASP.NET MVC 3, and is a true “release candidate” in that we are hoping to not make any more code changes with it.  We are publishing it today so that people can do final testing with it, let us know if they find any last minute “showstoppers”, and start updating their apps to use it.  We will officially ship the final ASP.NET MVC 3 “RTM” build in January. Works with both VS 2010 and VS 2010 SP1 Beta Today’s ASP.NET MVC 3 RC2 release works with both the shipping version of Visual Studio 2010 / Visual Web Developer 2010 Express, as well as the newly released VS 2010 SP1 Beta.  This means that you do not need to install VS 2010 SP1 (or the SP1 beta) in order to use ASP.NET MVC 3.  It works just fine with the shipping Visual Studio 2010.  I’ll do a blog post next week, though, about some of the nice additional feature goodies that come with VS 2010 SP1 (including IIS Express and SQL CE support within VS) which make the dev experience for both ASP.NET Web Forms and ASP.NET MVC even better. Bugs and Perf Fixes Today’s ASP.NET MVC 3 RC2 build contains many bug fixes and performance optimizations.  Our latest performance tests indicate that ASP.NET MVC 3 is now faster than ASP.NET MVC 2, and that existing ASP.NET MVC applications will experience a slight performance increase when updated to run using ASP.NET MVC 3. Final Tweaks and Fit-N-Finish In addition to bug fixes and performance optimizations, today’s RC2 build contains a number of last-minute feature tweaks and “fit-n-finish” changes for the new ASP.NET MVC 3 features.  The feedback and suggestions we’ve received during the public previews has been invaluable in guiding these final tweaks, and we really appreciate people’s support in sending this feedback our way.  Below is a short-list of some of the feature changes/tweaks made between last month’s ASP.NET MVC 3 RC release and today’s ASP.NET MVC 3 RC2 release: jQuery updates and addition of jQuery UI The default ASP.NET MVC 3 project templates have been updated to include jQuery 1.4.4 and jQuery Validation 1.7.  We are also excited to announce today that we are including jQuery UI within our default ASP.NET project templates going forward.  jQuery UI provides a powerful set of additional UI widgets and capabilities.  It will be added by default to your project’s \scripts folder when you create new ASP.NET MVC 3 projects. Improved View Scaffolding The T4 templates used for scaffolding views with the Add-View dialog now generates views that use Html.EditorFor instead of helpers such as Html.TextBoxFor. This change enables you to optionally annotate models with metadata (using data annotation attributes) to better customize the output of your UI at runtime. The Add View scaffolding also supports improved detection and usage of primary key information on models (including support for naming conventions like ID, ProductID, etc).  For example: the Add View dialog box uses this information to ensure that the primary key value is not scaffold as an editable form field, and that links between views are auto-generated correctly with primary key information. The default Edit and Create templates also now include references to the jQuery scripts needed for client validation.  Scaffold form views now support client-side validation by default (no extra steps required).  Client-side validation with ASP.NET MVC 3 is also done using an unobtrusive javascript approach – making pages fast and clean. [ControllerSessionState] –> [SessionState] ASP.NET MVC 3 adds support for session-less controllers.  With the initial RC you used a [ControllerSessionState] attribute to specify this.  We shortened this in RC2 to just be [SessionState]: Note that in addition to turning off session state, you can also set it to be read-only (which is useful for webfarm scenarios where you are reading but not updating session state on a particular request). [SkipRequestValidation] –> [AllowHtml] ASP.NET MVC includes built-in support to protect against HTML and Cross-Site Script Injection Attacks, and will throw an error by default if someone tries to post HTML content as input.  Developers need to explicitly indicate that this is allowed (and that they’ve hopefully built their app to securely support it) in order to enable it. With ASP.NET MVC 3, we are also now supporting a new attribute that you can apply to properties of models/viewmodels to indicate that HTML input is enabled, which enables much more granular protection in a DRY way.  In last month’s RC release this attribute was named [SkipRequestValidation].  With RC2 we renamed it to [AllowHtml] to make it more intuitive: Setting the above [AllowHtml] attribute on a model/viewmodel will cause ASP.NET MVC 3 to turn off HTML injection protection when model binding just that property. Html.Raw() helper method The new Razor view engine introduced with ASP.NET MVC 3 automatically HTML encodes output by default.  This helps provide an additional level of protection against HTML and Script injection attacks. With RC2 we are adding a Html.Raw() helper method that you can use to explicitly indicate that you do not want to HTML encode your output, and instead want to render the content “as-is”: ViewModel/View –> ViewBag ASP.NET MVC has (since V1) supported a ViewData[] dictionary within Controllers and Views that enables developers to pass information from a Controller to a View in a late-bound way.  This approach can be used instead of, or in combination with, a strongly-typed model class.  The below code demonstrates a common use case – where a strongly typed Product model is passed to the view in addition to two late-bound variables via the ViewData[] dictionary: With ASP.NET MVC 3 we are introducing a new API that takes advantage of the dynamic type support within .NET 4 to set/retrieve these values.  It allows you to use standard “dot” notation to specify any number of additional variables to be passed, and does not require that you create a strongly-typed class to do so.  With earlier previews of ASP.NET MVC 3 we exposed this API using a dynamic property called “ViewModel” on the Controller base class, and with a dynamic property called “View” within view templates.  A lot of people found the fact that there were two different names confusing, and several also said that using the name ViewModel was confusing in this context – since often you create strongly-typed ViewModel classes in ASP.NET MVC, and they do not use this API.  With RC2 we are exposing a dynamic property that has the same name – ViewBag – within both Controllers and Views.  It is a dynamic collection that allows you to pass additional bits of data from your controller to your view template to help generate a response.  Below is an example of how we could use it to pass a time-stamp message as well as a list of all categories to our view template: Below is an example of how our view template (which is strongly-typed to expect a Product class as its model) can use the two extra bits of information we passed in our ViewBag to generate the response.  In particular, notice how we are using the list of categories passed in the dynamic ViewBag collection to generate a dropdownlist of friendly category names to help set the CategoryID property of our Product object.  The above Controller/View combination will then generate an HTML response like below.    Output Caching Improvements ASP.NET MVC 3’s output caching system no longer requires you to specify a VaryByParam property when declaring an [OutputCache] attribute on a Controller action method.  MVC3 now automatically varies the output cached entries when you have explicit parameters on your action method – allowing you to cleanly enable output caching on actions using code like below: In addition to supporting full page output caching, ASP.NET MVC 3 also supports partial-page caching – which allows you to cache a region of output and re-use it across multiple requests or controllers.  The [OutputCache] behavior for partial-page caching was updated with RC2 so that sub-content cached entries are varied based on input parameters as opposed to the URL structure of the top-level request – which makes caching scenarios both easier and more powerful than the behavior in the previous RC. @model declaration does not add whitespace In earlier previews, the strongly-typed @model declaration at the top of a Razor view added a blank line to the rendered HTML output. This has been fixed so that the declaration does not introduce whitespace. Changed "Html.ValidationMessage" Method to Display the First Useful Error Message The behavior of the Html.ValidationMessage() helper was updated to show the first useful error message instead of simply displaying the first error. During model binding, the ModelState dictionary can be populated from multiple sources with error messages about the property, including from the model itself (if it implements IValidatableObject), from validation attributes applied to the property, and from exceptions thrown while the property is being accessed. When the Html.ValidationMessage() method displays a validation message, it now skips model-state entries that include an exception, because these are generally not intended for the end user. Instead, the method looks for the first validation message that is not associated with an exception and displays that message. If no such message is found, it defaults to a generic error message that is associated with the first exception. RemoteAttribute “Fields” -> “AdditionalFields” ASP.NET MVC 3 includes built-in remote validation support with its validation infrastructure.  This means that the client-side validation script library used by ASP.NET MVC 3 can automatically call back to controllers you expose on the server to determine whether an input element is indeed valid as the user is editing the form (allowing you to provide real-time validation updates). You can accomplish this by decorating a model/viewmodel property with a [Remote] attribute that specifies the controller/action that should be invoked to remotely validate it.  With the RC this attribute had a “Fields” property that could be used to specify additional input elements that should be sent from the client to the server to help with the validation logic.  To improve the clarity of what this property does we have renamed it to “AdditionalFields” with today’s RC2 release. ViewResult.Model and ViewResult.ViewBag Properties The ViewResult class now exposes both a “Model” and “ViewBag” property off of it.  This makes it easier to unit test Controllers that return views, and avoids you having to access the Model via the ViewResult.ViewData.Model property. Installation Notes You can download and install the ASP.NET MVC 3 RC2 build here.  It can be installed on top of the previous ASP.NET MVC 3 RC release (it should just replace the bits as part of its setup). The one component that will not be updated by the above setup (if you already have it installed) is the NuGet Package Manager.  If you already have NuGet installed, please go to the Visual Studio Extensions Manager (via the Tools –> Extensions menu option) and click on the “Updates” tab.  You should see NuGet listed there – please click the “Update” button next to it to have VS update the extension to today’s release. If you do not have NuGet installed (and did not install the ASP.NET MVC RC build), then NuGet will be installed as part of your ASP.NET MVC 3 setup, and you do not need to take any additional steps to make it work. Summary We are really close to the final ASP.NET MVC 3 release, and will deliver the final “RTM” build of it next month.  It has been only a little over 7 months since ASP.NET MVC 2 shipped, and I’m pretty amazed by the huge number of new features, improvements, and refinements that the team has been able to add with this release (Razor, Unobtrusive JavaScript, NuGet, Dependency Injection, Output Caching, and a lot, lot more).  I’ll be doing a number of blog posts over the next few weeks talking about many of them in more depth. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• Explain Model View Controller

  - by Channel72

  My experience with developing dynamic websites is limited mostly to Java servlets. I've used Tomcat to develop various Java servlets, and I wouldn't hesitate to say that I'm reasonably proficient with this technology, as well as with client-side HTML/CSS/Javascript for the front-end. When I think "dynamic website", I think: user requests a URL with a query string, server receives the query, and then proceeds to output HTML dynamically in order to respond to the query. This often involves communication with a database in order to fetch requested data for display. This is basically the idea behind the doGet method of a Java HttpServlet. But these days, I'm hearing more and more about newer frameworks such as Django and Ruby on Rails, all of which take advantage of the "Model View Controller" architecture. I've read various articles which explain MVC, but I'm having trouble really understanding the benefits. I understand that the general idea is to separate business logic from UI logic, but I fail to see how this is anything really different from normal web programming. Web programming, by it's very nature, forces you to separate business logic (back-end server-side programming) from UI programming (client-side HTML or Javascript), because the two exist in entirely different spheres of programming. Question: What does MVC offer over something like a Java servlet, and more importantly, what exactly is MVC and how is it different from what you would normally do to develop a dynamic website using a more traditional approach such as a Java servlet (or even something older like CGI). If possible, when explaining MVC, please provide an example which illustrates how MVC is applied to the web development process, and how it is beneficial.

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• July, the 31 Days of SQL Server DMO’s – Day 28 (sys.dm_db_stats_properties)

  - by Tamarick Hill

  The sys.dm_db_stats_properties Dynamic Management Function returns information about the statistics that are currently on your database objects. This function takes two parameters, an object_id and a stats_id. Let’s have a look at the result set from this function against the AdventureWorks2012.Sales.SalesOrderHeader table. To obtain the object_id and stats_id I will use a CROSS APPLY with the sys.stats system table. SELECT sp.* FROM sys.stats s CROSS APPLY sys.dm_db_stats_properties(s.object_id, s.Stats_id) sp WHERE sp.object_id = object_id('Sales.SalesOrderHeader') The first two columns returned by this function are the object_id and the stats_id columns. The next column, ‘last_updated’, gives you the date and the time that a particular statistic was last updated. The next column, ‘rows’, gives you the total number of rows in the table as of the last statistic update date. The ‘rows_sampled’ column gives you the number of rows that were sampled to create the statistic. The ‘steps’ column represents the number of specific value ranges from the statistic histogram. The ‘unfiltered_rows’ column represents the number of rows before any filters are applied. If a particular statistic is not filtered, the ‘unfiltered_rows’ column will always equal the ‘rows’ column. Lastly we have the ‘modification_counter’ column which represents the number of modification to the leading column in a given statistic since the last time the statistic was updated. Probably the most important column from this Dynamic Management Function is the ‘last_updated’ column. You want to always ensure that you have accurate and updated statistics on your database objects. Accurate statistics are vital for the query optimizer to generate efficient and reliable query execution plans. Without accurate and updated statistics, the performance of your SQL Server would likely suffer. For more information about this Dynamic Management Function, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/jj553546.aspx Folllow me on Twitter @PrimeTimeDBA

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• Unable to cast transparent proxy to type &lt;type&gt;

  - by Rick Strahl

  This is not the first time I've run into this wonderful error while creating new AppDomains in .NET and then trying to load types and access them across App Domains. In almost all cases the problem I've run into with this error the problem comes from the two AppDomains involved loading different copies of the same type. Unless the types match exactly and come exactly from the same assembly the typecast will fail. The most common scenario is that the types are loaded from different assemblies - as unlikely as that sounds. An Example of Failure To give some context, I'm working on some old code in Html Help Builder that creates a new AppDomain in order to parse assembly information for documentation purposes. I create a new AppDomain in order to load up an assembly process it and then immediately unload it along with the AppDomain. The AppDomain allows for unloading that otherwise wouldn't be possible as well as isolating my code from the assembly that's being loaded. The process to accomplish this is fairly established and I use it for lots of applications that use add-in like functionality - basically anywhere where code needs to be isolated and have the ability to be unloaded. My pattern for this is: Create a new AppDomain Load a Factory Class into the AppDomain Use the Factory Class to load additional types from the remote domain Here's the relevant code from my TypeParserFactory that creates a domain and then loads a specific type - TypeParser - that is accessed cross-AppDomain in the parent domain:public class TypeParserFactory : System.MarshalByRefObject,IDisposable { …/// <summary> /// TypeParser Factory method that loads the TypeParser /// object into a new AppDomain so it can be unloaded. /// Creates AppDomain and creates type. /// </summary> /// <returns></returns> public TypeParser CreateTypeParser() { if (!CreateAppDomain(null)) return null; /// Create the instance inside of the new AppDomain /// Note: remote domain uses local EXE's AppBasePath!!! TypeParser parser = null; try { Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; parser = (TypeParser) this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); } catch (Exception ex) { this.ErrorMessage = ex.GetBaseException().Message; return null; } return parser; } private bool CreateAppDomain(string lcAppDomain) { if (lcAppDomain == null) lcAppDomain = "wwReflection" + Guid.NewGuid().ToString().GetHashCode().ToString("x"); AppDomainSetup setup = new AppDomainSetup(); // *** Point at current directory setup.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory; //setup.PrivateBinPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "bin"); this.LocalAppDomain = AppDomain.CreateDomain(lcAppDomain,null,setup); // Need a custom resolver so we can load assembly from non current path AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(CurrentDomain_AssemblyResolve); return true; } …} Note that the classes must be either [Serializable] (by value) or inherit from MarshalByRefObject in order to be accessible remotely. Here I need to call methods on the remote object so all classes are MarshalByRefObject. The specific problem code is the loading up a new type which points at an assembly that visible both in the current domain and the remote domain and then instantiates a type from it. This is the code in question:Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; parser = (TypeParser) this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); The last line of code is what blows up with the Unable to cast transparent proxy to type <type> error. Without the cast the code actually returns a TransparentProxy instance, but the cast is what blows up. In other words I AM in fact getting a TypeParser instance back but it can't be cast to the TypeParser type that is loaded in the current AppDomain. Finding the Problem To see what's going on I tried using the .NET 4.0 dynamic type on the result and lo and behold it worked with dynamic - the value returned is actually a TypeParser instance: Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; object objparser = this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); // dynamic works dynamic dynParser = objparser; string info = dynParser.GetVersionInfo(); // method call works // casting fails parser = (TypeParser)objparser; So clearly a TypeParser type is coming back, but nevertheless it's not the right one. Hmmm… mysterious.Another couple of tries reveal the problem however:// works dynamic dynParser = objparser; string info = dynParser.GetVersionInfo(); // method call works // c:\wwapps\wwhelp\wwReflection20.dll (Current Execution Folder) string info3 = typeof(TypeParser).Assembly.CodeBase; // c:\program files\vfp9\wwReflection20.dll (my COM client EXE's folder) string info4 = dynParser.GetType().Assembly.CodeBase; // fails parser = (TypeParser)objparser; As you can see the second value is coming from a totally different assembly. Note that this is even though I EXPLICITLY SPECIFIED an assembly path to load the assembly from! Instead .NET decided to load the assembly from the original ApplicationBase folder. Ouch! How I actually tracked this down was a little more tedious: I added a method like this to both the factory and the instance types and then compared notes:public string GetVersionInfo() { return ".NET Version: " + Environment.Version.ToString() + "\r\n" + "wwReflection Assembly: " + typeof(TypeParserFactory).Assembly.CodeBase.Replace("file:///", "").Replace("/", "\\") + "\r\n" + "Assembly Cur Dir: " + Directory.GetCurrentDirectory() + "\r\n" + "ApplicationBase: " + AppDomain.CurrentDomain.SetupInformation.ApplicationBase + "\r\n" + "App Domain: " + AppDomain.CurrentDomain.FriendlyName + "\r\n"; } For the factory I got: .NET Version: 4.0.30319.239wwReflection Assembly: c:\wwapps\wwhelp\bin\wwreflection20.dllAssembly Cur Dir: c:\wwapps\wwhelpApplicationBase: C:\Programs\vfp9\App Domain: wwReflection534cfa1f For the instance type I got: .NET Version: 4.0.30319.239wwReflection Assembly: C:\\Programs\\vfp9\wwreflection20.dllAssembly Cur Dir: c:\\wwapps\\wwhelpApplicationBase: C:\\Programs\\vfp9\App Domain: wwDotNetBridge_56006605 which clearly shows the problem. You can see that both are loading from different appDomains but the each is loading the assembly from a different location. Probably a better solution yet (for ANY kind of assembly loading problem) is to use the .NET Fusion Log Viewer to trace assembly loads.The Fusion viewer will show a load trace for each assembly loaded and where it's looking to find it. Here's what the viewer looks like: The last trace above that I found for the second wwReflection20 load (the one that is wonky) looks like this:*** Assembly Binder Log Entry (1/13/2012 @ 3:06:49 AM) *** The operation was successful. Bind result: hr = 0x0. The operation completed successfully. Assembly manager loaded from: C:\Windows\Microsoft.NET\Framework\V4.0.30319\clr.dll Running under executable c:\programs\vfp9\vfp9.exe --- A detailed error log follows. === Pre-bind state information === LOG: User = Ras\ricks LOG: DisplayName = wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null (Fully-specified) LOG: Appbase = file:///C:/Programs/vfp9/ LOG: Initial PrivatePath = NULL LOG: Dynamic Base = NULL LOG: Cache Base = NULL LOG: AppName = vfp9.exe Calling assembly : (Unknown). === LOG: This bind starts in default load context. LOG: Using application configuration file: C:\Programs\vfp9\vfp9.exe.Config LOG: Using host configuration file: LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\V4.0.30319\config\machine.config. LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind). LOG: Attempting download of new URL file:///C:/Programs/vfp9/wwReflection20.DLL. LOG: Assembly download was successful. Attempting setup of file: C:\Programs\vfp9\wwReflection20.dll LOG: Entering run-from-source setup phase. LOG: Assembly Name is: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null LOG: Binding succeeds. Returns assembly from C:\Programs\vfp9\wwReflection20.dll. LOG: Assembly is loaded in default load context. WRN: The same assembly was loaded into multiple contexts of an application domain: WRN: Context: Default | Domain ID: 2 | Assembly Name: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null WRN: Context: LoadFrom | Domain ID: 2 | Assembly Name: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null WRN: This might lead to runtime failures. WRN: It is recommended to inspect your application on whether this is intentional or not. WRN: See whitepaper http://go.microsoft.com/fwlink/?LinkId=109270 for more information and common solutions to this issue. Notice that the fusion log clearly shows that the .NET loader makes no attempt to even load the assembly from the path I explicitly specified. Remember your Assembly Locations As mentioned earlier all failures I've seen like this ultimately resulted from different versions of the same type being available in the two AppDomains. At first sight that seems ridiculous - how could the types be different and why would you have multiple assemblies - but there are actually a number of scenarios where it's quite possible to have multiple copies of the same assembly floating around in multiple places. If you're hosting different environments (like hosting the Razor Engine, or ASP.NET Runtime for example) it's common to create a private BIN folder and it's important to make sure that there's no overlap of assemblies. In my case of Html Help Builder the problem started because I'm using COM interop to access the .NET assembly and the above code. COM Interop has very specific requirements on where assemblies can be found and because I was mucking around with the loader code today, I ended up moving assemblies around to a new location for explicit loading. The explicit load works in the main AppDomain, but failed in the remote domain as I showed. The solution here was simple enough: Delete the extraneous assembly which was left around by accident. Not a common problem, but one that when it bites is pretty nasty to figure out because it seems so unlikely that types wouldn't match. I know I've run into this a few times and writing this down hopefully will make me remember in the future rather than poking around again for an hour trying to debug the issue as I did today. Hopefully it'll save some of you some time as well in the future.© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  COM   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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