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  • LVM mirroring VS RAID1

    - by syrenity
    Hi. Having learned a bit about LVM mirroring, I thought about replacing the current RAID-1 scheme I'm using to gain some flexibility. Problem is that according to what I found on the Internet, LVM is: 1) Slower then RAID-1, at least in reading (as only single volume being used for reading). 2) Non-reliable on power interrupts, and requires disk cache disabling for prevention of data loss. http://www.joshbryan.com/blog/2008/01/02/lvm2-mirrors-vs-md-raid-1/ Also it seems, at least to several setup guides I read (http://www.tcpdump.com/kb/os/linux/lvm-mirroring/intro.html), that one actually requires a 3rd disk for storing the LVM log. This makes the setup completely unusable on 2 disks installations, and lowers the amount of used mirror disks on higher amount of disks. Can anyone comment the above facts, and let me know his experience of using LVM mirroring? Thanks.

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  • Is learning how to use C (or C++) a requirement in order to be a good (excellent) programmer?

    - by blueberryfields
    When I first started to learn how to program, real programmers could write assembly in their sleep. Any serious schooling in computer science would include a hefty bit of training and practice in programming using assembly. That has since changed, to the point where I see Computer Science degrees with assembly, if included at all, is relegated to one assignment, and one chapter, for a total of two weeks' work out of 4 years' schooling. C/C++ programming seems to have followed a similar path. I'm no longer surprised to interview university graduates who have not spent more than two weeks programming in C++, and have only read of C in a book somewhere. While the most serious CS degrees still seem to include significant time learning and using one or both of the languages, the trend is clearly towards less enforced C/C++ in school. It's clearly possible to make a career producing good work without ever reading or writing a single line of C or C++ code. Given all of that, is learning the two languages worth the effort? Are they at all required to excel? (beyond the obvious, non-language specific advice, such as "a good selection of languages is probably important for a comprehensive education", and "it's probably a good idea to keep trying out and learning new languages throughout a programmers' career, just to stretch the gray cells")

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  • Separation of memory oriented process and CPU oriented process

    - by Jeevan Dongre
    I am develops guy working for an e-commerce company I am running my e-commerce application built using ruby on rails spree commerce. I am presently running 2 medium instances in the production. One is a high memory instance which has 3.8 RAM and single Core CPU and another one is high CPU instance which has Dual Core CPU. Basically AWS calls it has m1.medium and c1.medium instance respectively. My question is it possible to separate the processes according the cpu intense and memory intense? So that all the cpu intense process can be made run in high cpu instance and all the memory intense process can be made to run in the high memory instances. Is any tool available to identify those process. Kindly give me some heads up. Thank you

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  • How to create shared home directories across multiple computers?

    - by Joe D
    I know there are ways to share a folder across computers making it easy to move files. But I was wondering how one would setup a single login which lets you access the same files regardless of which machine you login on? What I would like is something similar to something you would see in a college campus where students login on machines in the lab and see their files regardless of which machine they use. I know there are server involved here. I have a need to create this on a smaller scale where we have a few computers available (and one of these could act as the server if needed and host the files) that every one shares. Note, the specific install of software might be different on each computer but the login and OS are the same. Since some computers have additional capability that our group members will need to use at rotating schedules (software licenses or hardware components, etc.). I have not done this before, so I would appreciate detailed instructions if possible or a reference to a guide that describes this. Thanks in advance.

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  • Serving static web files off a non-standard port

    - by Nimmy Lebby
    I'm close to deploying a Django project to production. I'm looking over some infrastructure decisions. Something that came up was serving static files with a different server such as lighttpd. However, we're starting off with a single dedicated server so our only option would be to use a non-standard port for the static file webserver. Is there precedence for this? I.e. Does anyone "big" do this? Any particular port I should use or shy away from using? Can anyone thing of some downsides of going this route?

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  • World Backup Day

    - by red(at)work
    Here at Red Gate Towers, the SQL Backup development team have been hunkered down in their shed for the last few months, with the toolbox, blowtorch and chamois leather out, upgrading SQL Backup. When we started, autumn leaves were falling. Now we're about to finish, spring flowers are budding. If not quite a gleaming new machine, at the very least a familiar, reliable engine with some shiny new bits on it will trundle magnificently out of the workshop. One of the interesting things I've noticed about working on software development teams is that the team is together for so long 'implementing' stuff - designing, coding, testing, fixing bugs and so on - that you occasionally forget why you're doing what you're doing. Doubt creeps in. It feels like a long time since we launched this project in a fanfare of optimism and enthusiasm, and all that clarity of purpose and mission "yee-haw" has dissipated with the daily pressures of development. Every now and again, we look up from our bunker and notice all those thousands of users out there, with their different configurations and working practices and each with their own set of problems and requirements, and we ask ourselves "does anyone care about what we're doing?" Has the world moved on while we've been busy? Could we have been doing something more useful with the time and talent of all these excellent people we've assembled? In truth, you can research and test and validate all you like, but you never really know if you've done the right thing (or at least, something valuable for some users) until you release. All projects suffer this insecurity. If they don't, maybe you're not worrying enough about what you're building. The two enemies of software development are certainty and complacency. Oh, and of course, rival teams with Nerf guns. The goal of SQL Backup 7 is to make it so easy to schedule regular restores of your backups that you have no excuse not to. Why schedule a restore? Because your data is not as good as your last backup. It's only as good as your last successful restore. If you're not checking your backups by restoring them and running an integrity check on the database, you're only doing half the job. It seems that most DBAs know that this is best practice, but it can be tricky and time-consuming to set up, so it's one of those tasks that can get forgotten in the midst all the other demands on their time. Sometimes, they're just too busy firefighting. But if it was simple to do? That was our inspiration for SQL Backup 7. So it was heartening to read Brent Ozar's blog post the other day about World Backup Day. To be honest, I'd never heard of World Backup Day (Talk Like a Pirate Day, yes, but not this one); however, its emphasis on not just backing up your data but checking the validity of those backups was exactly the same message we had in mind when building SQL Backup 7. It's printed on a piece of A3 above our planning board - "Make backup verification so easy to do that no DBA has an excuse for not doing it" It's the missing piece that completes the puzzle. Simple idea, great concept, useful feature, but, as it turned out, far from straightforward to implement. The problem is the future. As Marty McFly discovered over the course of three movies, the future is uncertain and hard to predict - so when you are scheduling a restore to take place an hour, day, week or month after the backup, there are all kinds of questions that you wouldn't normally have to consider. Where will this backup live? Will it even exist at the time? Will it be split into multiple files? What will the file names be? Will it be encrypted? What files should it be restored to? SQL Backup needs to know what to expect at the time the restore job is actually run. Of course, a DBA will know the answer to all these questions, but to deliver the whole point of version 7, we wanted to make it easy for them to input that information into SQL Backup. We think we've done that. When you create your scheduled backup job, there is now an option to create a "reminder" to follow it up with a scheduled restore to verify the resulting backups. Actually, it's much more than a reminder, as it stores all the relevant data so you can click it and pre-populate the wizard with all the right settings to set up your verification restores. Simple. But, what do you think? We'd love you to try it. Post by Brian Harris

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  • Best practice, or generally best way to set up web-hosting server, permissions, etc.

    - by Jagot
    Hi, I'm about to set up a server upon which a friend and I will be hosting web sites, and I'll be using Debian. I've set up a LAMP solution many times just to using for local testing purposes, but never for actual production use. I was wondering what are the best practices are in terms of setting the server up, in reference specifically to accessing the web root directory. A couple of the options I have seen: Set up a single user account on the server for us both to use and use a virtual host to point to the somewhere in the home directory, e.g. /home/webdev/www. Set each of us up a user account, and grant permissions in some way to /var/www (What would be the best way? Set up a new group?) I want to get this right when I first set this up as there won't be any going back for a while once our first site is up and running. Appreciate any guidance in advance.

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  • Dealing with Fine-Grained Cache Entries in Coherence

    - by jpurdy
    On occasion we have seen significant memory overhead when using very small cache entries. Consider the case where there is a small key (say a synthetic key stored in a long) and a small value (perhaps a number or short string). With most backing maps, each cache entry will require an instance of Map.Entry, and in the case of a LocalCache backing map (used for expiry and eviction), there is additional metadata stored (such as last access time). Given the size of this data (usually a few dozen bytes) and the granularity of Java memory allocation (often a minimum of 32 bytes per object, depending on the specific JVM implementation), it is easily possible to end up with the case where the cache entry appears to be a couple dozen bytes but ends up occupying several hundred bytes of actual heap, resulting in anywhere from a 5x to 10x increase in stated memory requirements. In most cases, this increase applies to only a few small NamedCaches, and is inconsequential -- but in some cases it might apply to one or more very large NamedCaches, in which case it may dominate memory sizing calculations. Ultimately, the requirement is to avoid the per-entry overhead, which can be done either at the application level by grouping multiple logical entries into single cache entries, or at the backing map level, again by combining multiple entries into a smaller number of larger heap objects. At the application level, it may be possible to combine objects based on parent-child or sibling relationships (basically the same requirements that would apply to using partition affinity). If there is no natural relationship, it may still be possible to combine objects, effectively using a Coherence NamedCache as a "map of maps". This forces the application to first find a collection of objects (by performing a partial hash) and then to look within that collection for the desired object. This is most naturally implemented as a collection of entry processors to avoid pulling unnecessary data back to the client (and also to encapsulate that logic within a service layer). At the backing map level, the NIO storage option keeps keys on heap, and so has limited benefit for this situation. The Elastic Data features of Coherence naturally combine entries into larger heap objects, with the caveat that only data -- and not indexes -- can be stored in Elastic Data.

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  • Time Machine (archive) of pre-Leopard systems?

    - by benc
    I want to get off an older Mac OS X system permanently. It is an iBook G3, so that has two important characteristics: Power PC, not Intel based. Runs only Tiger, not Leopard. This means, as far as I can tell: Cannot run Time Machine directly. Here's the approach I have been contemplating: Mount the drive in Firewire mode. Back up the drive as a external drive to the Time Machine volume. Disconnect the drive (permanently). However, I'm concerned that this drive will eventually age out, when the Time Machine volume fills up, and the old-system-as-external-drive is gone. Would it be better to do a single backup with another utility, to shared disk?

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  • Strategies for avoiding SQL in your Controllers... or how many methods should I have in my Models?

    - by Keith Palmer
    So a situation I run into reasonably often is one where my models start to either: Grow into monsters with tons and tons of methods OR Allow you to pass pieces of SQL to them, so that they are flexible enough to not require a million different methods For example, say we have a "widget" model. We start with some basic methods: get($id) insert($record) update($id, $record) delete($id) getList() // get a list of Widgets That's all fine and dandy, but then we need some reporting: listCreatedBetween($start_date, $end_date) listPurchasedBetween($start_date, $end_date) listOfPending() And then the reporting starts to get complex: listPendingCreatedBetween($start_date, $end_date) listForCustomer($customer_id) listPendingCreatedBetweenForCustomer($customer_id, $start_date, $end_date) You can see where this is growing... eventually we have so many specific query requirements that I either need to implement tons and tons of methods, or some sort of "query" object that I can pass to a single -query(query $query) method... ... or just bite the bullet, and start doing something like this: list = MyModel-query(" start_date X AND end_date < Y AND pending = 1 AND customer_id = Z ") There's a certain appeal to just having one method like that instead of 50 million other more specific methods... but it feels "wrong" sometimes to stuff a pile of what's basically SQL into the controller. Is there a "right" way to handle situations like this? Does it seem acceptable to be stuffing queries like that into a generic -query() method? Are there better strategies?

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  • Android - big game universe

    - by user1641923
    I am new to an Android development, though I have much experience with Java, C++, PHP programming and a bit experience with vector graphics too (basic 3d Studio Max, Flash, etc). I am starting to work on an Android game. It is going to be a 2D space shooter/RPG, and I am not going to use any game engines and any 3D party libs. I really want to create a very large game universe, or even pseudo-infinite (without visible borders, as if it were a 2D projection of a sphere). It should include 10-12 clusters of 7-8 planets/other space objects and random amount of single asteroids/comets, which player can interact with and also not interactive background. I am looking for a least complicated aproach to create such a universe. My current ideas are: Simply create bitmaps with space scenery background so that they can be tiled seamlessly repeated and construct my 2D universe of this tiles, then place interactive objects (planets, other spaceships) on it. Using vector graphics. I would have a solid color background, some random background objects and gradients here and there. My problems here: Lack of knowledge of how well vector graphics is integrated in Android. Performance? Memory usage? Does Android manage big bitmaps well? Do all of the bitmaps have to be in memory during all game process? I am interested in technical details regarding each of the ideas and a suggestion, which I should go with.

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  • best way to send messages to all subscribers with multiple subscriptions and multiple providers

    - by coding_idiot
    I'm writing an application in which - Many users can subsribe to posts made by another users. So for a single publisher there can be many subscribers. When a message is posted by an user X, all users who have subscribed to messages of User X will be sent an email. How to achieve this ? I'm thinking of using publish-subscribe pattern. And then I came through JMS. Which is the best JMS implementation to use according to your experience ? Or else what else solution do you propose to the given problem ? Shall I go for a straight-forward solution ?: User x posts a message, I find all users (from database) who subscribe to user x and then for every user, I call the sendEmail() method. [EDIT] My intention here is not to send-emails. I'm really sorry if it wasn't clear. I also have to send kind of system-notifications apart from Email to all subscribers. Right now, I've implemented the email-sending as a threadPool

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  • ASP.NET design not SOLID

    - by w0051977
    SOLID principles are described here: http://en.wikipedia.org/wiki/SOLID_%28object-oriented_design%29 I am developing a large ASP.NET app. The previous developer created a few very large classes each with lots of different purposes. It is very difficult to maintain and extend. The classes are deployed to the web server along with the code behind files etc. I want to share a small amount of the app with another application. I am considering moving all of the classes of the ASP.NET web app to a DLL, so the small subset of functionality can be shared. I realise it would be better to only share the classes which contain code to be shared but because of the dependencies this is proving to be very difficult e.g. class A contains code that should be shared, however class A contains references to classes B, C, D, E, F, G etc, so class A cannot be shared on its own. I am planning to refactor the code in the future. As a temporary solution I am planning to convert all the classes into a single class library. Is this a bad idea and if so, is there an alternative? as I don't have time to refactor at the moment.

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  • How to get a list of all software that starts automatically when Windows 7 starts?

    - by hippietrail
    I know that under Windows there are multiple ways to get an app to autostart but I can never remember what all of those ways are. Is there a single unified way to bring up a list of all programs which are set to run themselves at startup and let me disable those I don't want? I'd prefer something built into Windows. I have Windows 7 Starter. But a free / open source / shareware tool would also be acceptable. (This time the software I want to prevent from autostarting is: MSN Messenger, Y! Messenger, and Vodaphone Mobile Broadband, which starts whether the dongle is inserted or not. None of these three are in Windows's "Startup" folder.)

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  • SPARC SuperCluster: new Software Enhancements announced on December 4

    - by Giuseppe Facchetti
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} December 4, 2012: Oracle Unveils Cloud and Consolidation Capabilities for Oracle SPARC SuperCluster The latest SPARC SuperCluster update offers layered, zero-overhead virtualization for Mission-Critical applications. Oracle today announced new software enhancements to the Oracle SPARC SuperCluster engineered system which enable customers to consolidate any combination of mission-critical enterprise databases, middleware and applications on a single system and rapidly deploy secure, self-service cloud services. For all the details, click here.

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  • Enable a program in Windows to run multiple times?

    - by user135490
    I've got this legacy software that only allows you to run one copy at a time, it detects that you have another session opened and it won't allow you to open a second instance. The problem is this is a cpu intensive program and it only use a single core. Is there any hacks or tweaks so I can trick it and open more than one instance? This would allow me to retire about 5 servers... I'm using Windows 2008 R2. I had to use cff explorer to enable the use more than 2GB RAM as the program crashes when it tries to use more than 2GB.

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  • Plug and Go NAS Storage

    - by graham.reeds
    My wife and I are separating. One of the things we need to extricate is the media we have accumulated over the years. So I am looking for a NAS solution that is a) relatively low-cost, b) reliable and c) easy for a non-geek to use (I don't want to be tech support). All it needs to do is hold our iTunes library, photos, course work and maybe some movies and TV shows that I currently have. She will be connecting via her Netbook. I have seen this thread but the reviews on Amazon aren't particularly favourable. Due to the need for simplicity, WHS and FreeNAS are none-starters. I need redundancy as if a single drive system was to die then she would lose her course work and photos. Is the ReadyNAS the only real solution out there?

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  • Install tmux on Mac OS X

    - by unixben
    This is a short run down on how to get tmux running on your Mac OS X system. The same methodology applies when compiling this on Solaris. What is tmux? According to the developer's page, "tmux is a terminal multiplexer: it enables a number of terminals (or windows), each running a separate program, to be created, accessed, and controlled from a single screen. tmux may be detached from a screen and continue running in the background, then later reattached". Why not just use screen? For me, the primary reason I switched to tmux from screen is the much easier configuration syntax that tmux offers. If you've ever struggled with formatting screen's caption or hardstatus line, then you will appreciate the ease with which you can achieve the same results in tmux. Preparing your environment You will need a C compiler installed. I believe that OS X ships by default with GNU make, but if not, then you will need to obtain it or use Xcode. Download the sources While I'm putting all this together, I like to keep everything neatly tucked away in a build directory. mkdir ~/build cd ~/build curl -OL http://downloads.sourceforge.net/tmux/tmux-1.5.tar.gz curl -OL http://downloads.sourceforge.net/project/levent/libevent/libevent-2.0/libevent-2.0.16-stable.tar.gz Unpack the sources tar xzf tmux-1.5.tar.gz tar xzf libevent-2.0.16-stable.tar.gz Compiling libevent cd libevent-2.0.16-stable ./configure --prefix=/opt make sudo make install Compiling tmux cd ../tmux-1.5 LDFLAGS="-L/opt/lib" CPPFLAGS="-I/opt/include" LIBS="-lresolv" ./configure --prefix=/opt make sudo make install That's all there is to it!

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  • Slow http traffic between VMWare guest and host.

    - by toluju
    I have a web application running as an http server inside the VMWare guest OS, and I'm trying to access the content from the host OS. The guest is running Ubuntu, and the host is running Windows XP. The problem is, when I try to access the application from a browser in the host OS, the content takes a very long time to load (up to a minute for a single page). A browser in the guest OS can access the application with no problems. I've tried using both NAT and bridged networking, but the results are the same. The Windows firewall is turned off. The connection itself appears fine, as ping requests from guest to host as well as host to guest complete without errors or delays. Both guest and host can access the external Internet connection without a problem. I'm using VMWare Player. Any ideas?

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  • Is there some standard way to publish a calendar feed?

    - by CMP
    For a web application I am working on, I would like to be able to give the user a single url that they can enter into the calendar application of their choosing to have events from our application show up in their calendar. Most other sites I have seen that do similar things will have a one time download of an .ics file that can be imported. If I have to require my users to download a new file every time the schedule changes, it sort of defeats the purpose of having the feed at all. The calendar can change many many times a day. What I would really like is something like rss where their calendar program can look up a url and automatically see the most recent data. Does anything like this exist? Our main target is mobile devices, so it really should be supported by iCal and google Calendar. Anything else is bonus.

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  • Odd FTP ASCII/BINARY transfer behavior after migrating to a new server

    - by Incognita Mundi
    I recently got a dedicated server and after migration to the new machine I started noticing problems with file transfers. My FTP client, despite being set to auto, keeps uploading php files in binary mode and the content of those files is messed up. Since I mostly upload files of different kinds it would be annoying to change from binary to ASCII every single time, beside, I never had such problems. What could be the cause of this behavior? My dedicated server runs CENTOS 6.4 and the ftp server is Pure-FTPd. I tried different FTP clients and they all have the same problem so I assume is soem misconfiguration on the server side. Thanks

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  • MySQL Locking Up

    - by Ian
    I've got a innodb table that gets a lot of reads and almost no writes (like, 1 write for every 400,000 reads approx). I'm running into a pretty big problem though when I do INSERT into the table. MySQL completely locks up. It uses 100% cpu, and every single other table (in other databases even) have their statuses set to "Locked" until the INSERT is done. This is a big problem because MySQL stays locked up for up to 4 minutes. I'm using version 5.1.47 (rpm from mysql.com). Any ideas?

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  • Centralizing a resource file among multiple projects in one solution (C#/WPF)

    - by MarkPearl
    One of the challenges one faces when doing multi language support in WPF is when one has several projects in one solution (i.e. a business layer & ui layer) and you want multi language support. Typically each solution would have a resource file – meaning if you have 3 projects in a solution you will have 3 resource files.   For me this isn’t an ideal solution, as you normally want to send the resource files to a translator and the more resource files you have, the more fragmented the dictionary will be and the more complicated it will be for the translator. This can easily be overcome by creating a single project that just holds your translation resources and then exposing it to the other projects as a reference as explained in the following steps. Step 1 Step 1 -  Add a class library to your solution that will contain just the resource files. Your solution will now have an additional project as illustrated below. Step 2 Reference this project to the other projects. Step 3 Move all the resources from the other resource files to the translation projects resource file. Step 4 Set the translations projects resource files access modifier to public. Step 5 Reference all other projects to use the translation resource file instead of their local resource file. To do this in xaml you would need to expose the project as a namespace at the top of the xaml file… note that the example below is for a project called MaxCutLanguages – you need to put the correct project name in its place.   xmlns:MaxCutLanguages="clr-namespace:MaxCutLanguages;assembly=MaxCutLanguages"   And then in the actual xaml you need to replace any text with a reference to the resource file. <TextBlock Text="{x:Static MaxCutLanguages:Properties.Resources.HelloWorld}"/> End Result You can now delete all the resource files in the other projects as you now have one centralized resource file.

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  • Is LSB's init script function "start_daemon" really used for real daemons or should I stick to start-stop-daemon?

    - by Fred
    In the context of init scripts, according to the LSB specification, "Each conforming init script shall execute the commands in the file /lib/lsb/init-function", which then defines a couple of functions to be used when using daemons. One of those functions is start_daemon, which obviously "runs the specified program as a daemon" while checking if the daemon is already running. I'm in the process of daemonizing a service app of mine, and I'm looking at how other daemons are run to try to "fit in". In the process of looking how it's done elsewhere, I noticed that not a single daemon on my Ubuntu 10.04 machine uses start_daemon. They all call start-stop-daemon directly. Same goes for my Fedora 14 machine. Should I try to play nice and be the first one to use start_daemon, or is there really no point and start-stop-daemon is the way to go since everybody is already using that? Why is there no daemons using LSB's functions?

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  • Adobe Reader - Content Preparation progress

    - by kubal5003
    Hello, I was wondering recently if is it just me or anyone else noticed it: why Adobe Reader after opening every single document displays "Content preparation" window with progress bar and it lasts for ages.. ? On linux pdf readers work hell lot better (faster), on windows other readers also work faster. Some years back in the past Adobe Reader also used to be quick. What has happened? PDF files aren't bigger/more complex compared to 3-4 years ago. Computers are at least dual core and with much more ram and displaying pdf files is getting slower and slower..

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