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  • Windows 7, going crazy with environment variables

    - by roymustang86
    So, I am trying to learn java. I installed the JDK and proceeded to write a few programs. Each time, I have to give the path to javac.exe to compile the .java file. SO, I decided to tweak the %PATH% variable. And no matter what I change it to, it doesn't work. when I do an echo %PATH%, I get 'Program' is not recognized as an internal or external command, operable program or batch file. This is my Path variable contents : C:\app\product\11.1.0\client_1\bin;%CommonProgramFiles%\Microsoft Shared\Windows Live;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;"C:\Program Files (x86)\Common Files\Roxio Shared\DLLShared\";"C:\Program Files\Broadcom\Broadcom 802.11";"C:\Program Files (x86)\Common Files\Roxio Shared\OEM\DLLShared\";"C:\Program Files (x86)\Common Files\Roxio Shared\OEM\DLLShared\";"C:\Program Files (x86)\Common Files\Roxio Shared\OEM\12.0\DLLShared\";"C:\Program Files (x86)\Roxio\OEM\AudioCore\";"C:\Program Files (x86)\Intel\Services\IPT\" How do I work around this? the double quotes were not there before, I added it thinking the space was the problem.

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  • Windows 2003 Server - Can I map a folder to another folder on the same server?

    - by TheCleaner
    Scenario: I have a server that was running low on space. We have an external iscsi SAN that it now has a LUN on and connected to the server as E:\ We are moving the PHOTOS folder from the old location on D:\ to the new E:. That new drive is being shared out as "ARCHIVE". So: \server\shared\photos now becomes \server\archive\photos I can easily place a shortcut in the original location saying "DOUBLE CLICK HERE FOR THE PHOTOS", but it isn't ideal. What I'd like is to be able to have \server\shared\photos simply point to \server\archive\photos. So that if someone wants to map a drive to \server\shared and then browse to the photos folder once in there they will see what is in the \server\archive\photos location. Is that possible? I was thinking about SUBST or DFS, but I don't think either of those will do it.

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  • Path Environmental Variable errors

    - by roymustang86
    So, I am trying to learn java. I installed the JDK and proceeded to write a few programs. Each time, I have to give the path to javac.exe to compile the .java file. SO, I decided to tweak the %PATH% variable. And no matter what I change it to, it doesn't work. when I do an echo %PATH%, I get 'Program' is not recognized as an internal or external command, operable program or batch file. This is my Path variable contents : C:\app\product\11.1.0\client_1\bin;%CommonProgramFiles%\Microsoft Shared\Windows Live;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;"C:\Program Files (x86)\Common Files\Roxio Shared\DLLShared\";"C:\Program Files\Broadcom\Broadcom 802.11";"C:\Program Files (x86)\Common Files\Roxio Shared\OEM\DLLShared\";"C:\Program Files (x86)\Common Files\Roxio Shared\OEM\DLLShared\";"C:\Program Files (x86)\Common Files\Roxio Shared\OEM\12.0\DLLShared\";"C:\Program Files (x86)\Roxio\OEM\AudioCore\";"C:\Program Files (x86)\Intel\Services\IPT\" How do I work around this? the double quotes were not there before, I added it thinking the space was the problem.

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  • Allowing Apache in Ubuntu to access files in NTFS hard drive

    - by lyrae
    I have LAMP running in Ubuntu. However, my files are located on a separate NTFS hard drive (/media/shared/mysite/). going to http://localhost gives me a 403 how can i, securely, allow apache to read/write the NTFS disk? 'shared' is currently being mounted when system boots. here's the entry in fstab: /dev/sda1 /media/shared ntfs-3g quiet,defaults,locale=en_US.utf8,umask=000 0 0

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  • forfiles.exe scripting

    - by PHLiGHT
    I'm looking to automatically delete files older than 7 days old with forfiles. The code below works when I manually do it it and respond yes to deleting the files. How can I incorporate the yes into this? This is the output E:\Documents and Settings\Administratorforfiles -p "H:\SHARED\Sca ns" -s -m . -d -7 -c "cmd /c del @path" Could Not Find H:\SHARED\Scans.DS_Store H:\SHARED\Scans\XXX\DOC006.XSM*, Are you sure (Y/N)?

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  • Is it possible to view the contents of an underlying NFS mount without unmounting the NFS content?

    - by Brent
    I have a shared directory on a server - let's call it /home/shared - which is mounted with content from another server via nfs. When it is unmounted /home/shared is supposed to be empty - however, running du -x on the directory indicates that it is not empty. I cannot unmount the NFS content to inspect the mount point, since it is in use by others. Is there any way that I can view/edit the contents of the actual mount point (not the NFS content) while leaving the NFS content mounted for others to use?

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  • Folder access per user

    - by user137670
    I have sbs 2003 r2. I have a shared folder (s-drive) for all shared info for everyone. when user is on shared folder, you see size of folder 230G. I have one user that only sees 1g when on shared folder. I have pcs using XP pro. Have check quota and they say no quota limit checked. I had user use a different pc and still same result. With this I looked at server and users profile and compared with user that did not have problem. could not see anything different. what did I miss in some option or do I have to rebuild user? I have tried google with different terms but have not gotten any good clues

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  • Confusion for mime files: magic, magic.mgc, magic.mime

    - by Florence Foo
    I'm using Ubuntu. I'm trying to use ruby gem 'shared-mime-info' for an application I'm writing. I understand that magic.mgc is a compiled version of magic file which has magic number definitions for the different file types. BUT I don't understand why is it /usr/share/mime/magic is in binary format instead of just normal text file with each parameters separated by white space like everywhere else I'm finding on the internet when it's referencing this file? The /usr/share/mime/magic has the word 'MIME-Magic' at the beginning of the file and prioritize the rest of the stuff like. So it doesn't look like magic.mgc at all. [100:application/vnd.scribus] >1=^@^KSCRIBUSUTF8 [90:application/vnd.stardivision.writer] >2089=^@ shared-mime-info seems to want a magic file in the binary non compiled format as above and I wanted to add definition for DOCX but how does one update or generate this file without using a hex editor? There is a reference to the magic file I found at: http://standards.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-latest.html And it mention this file is updated with update-mime-database but what if I just want to add some new entry to it. hex editor? Anyway I ended up using hexer to make a new magic file in ~/.local/share/mime/ with only the entry I wanted to add and the MIME-Magic header. Seems to work (assuming I will ever deal with docx for now). 00000000: 4d 49 4d 45 2d 4d 61 67 69 63 00 0a 5b 36 30 3a MIME-Magic..[60: 00000010: 61 70 70 6c 69 63 61 74 69 6f 6e 2f 76 6e 64 2e application/vnd. 00000020: 6f 70 65 6e 78 6d 6c 66 6f 72 6d 61 74 73 2d 6f openxmlformats-o 00000030: 66 66 69 63 65 64 6f 63 75 6d 65 6e 74 2e 77 6f fficedocument.wo 00000040: 72 64 70 72 6f 63 65 73 73 69 6e 67 6d 6c 2e 64 rdprocessingml.d 00000050: 6f 63 75 6d 65 6e 74 5d 0a 3e 30 3d 00 08 50 4b ocument].>0=..PK 00000060: 03 04 14 00 06 00 0a -- -- -- -- -- -- -- -- -- .......---------

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  • Windows Azure Evolution - Web Sites (aka Antares) Part 1

    - by Shaun
    This is the 3rd post of my Windows Azure Evolution series, focus on the new features and enhancement which was alone with the Windows Azure Platform Upgrade June 2012, announced at the MEET Windows Azure event on 7th June. In the first post I introduced the new preview developer portal and how to works for the existing features such as cloud services, storages and SQL databases. In the second one I talked about the Windows Azure .NET SDK 1.7 on the latest Visual Studio 2012 RC on Windows 8. From this one I will begin to introduce some new features. Now let’s have a look on the first one of them, Windows Azure Web Sites.   Overview Windows Azure Web Sites (WAWS), as known as Antares, was a new feature still in preview stage in this upgrade. It allows people to quickly and easily deploy websites to a highly scalable cloud environment, uses the languages and open source apps of the choice then deploy such as FTP, Git and TFS. It also can be integrated with Windows Azure services like SQL Database, Caching, CDN and Storage easily. After read its introduction we may have a question: since we can deploy a website from both cloud service web role and web site, what’s the different between them? So, let’s have a quick compare.   CLOUD SERVICE WEB SITE OS Windows Server Windows Server Virtualization Windows Azure Virtual Machine Windows Azure Virtual Machine Host IIS IIS Platform ASP.NET WebForm, ASP.NET MVC, WCF ASP.NET WebForm, ASP.NET MVC, PHP Language C#, VB.NET C#, VB.NET, PHP Database SQL Database SQL Database, MySQL Architecture Multi layered, background worker, message queuing, etc.. Simple website with backend database. VS Project Windows Azure Cloud Service ASP.NET Web Form, ASP.NET MVC, etc.. Out-of-box Gallery (none) Drupal, DotNetNuke, WordPress, etc.. Deployment Package upload, Visual Studio publish FTP, Git, TFS, WebMatrix Compute Mode Dedicate VM Shared Across VMs, Dedicate VM Scale Scale up, scale out Scale up, scale out As you can see, there are many difference between the cloud service and web site, but the main point is that, the cloud service focus on those complex architecture web application. For example, if you want to build a website with frontend layer, middle business layer and data access layer, with some background worker process connected through the message queue, then you should better use cloud service, since it provides full control of your code and application. But if you just want to build a personal blog or a  business portal, then you can use the web site. Since the web site have many galleries, you can create them even without any coding and configuration. David Pallmann have an awesome figure explains the benefits between the could service, web site and virtual machine.   Create a Personal Blog in Web Site from Gallery As I mentioned above, one of the big feature in WAWS is to build a website from an existing gallery, which means we don’t need to coding and configure. What we need to do is open the windows azure developer portal and click the NEW button, select WEB SITE and FROM GALLERY. In the popping up windows there are many websites we can choose to use. For example, for personal blog there are Orchard CMS, WordPress; for CMS there are DotNetNuke, Drupal 7, mojoPortal. Let’s select WordPress and click the next button. The next step is to configure the web site. We will need to specify the DNS name and select the subscription and region. Since the WordPress uses MySQL as its backend database, we also need to create a MySQL database as well. Windows Azure Web Sites utilize ClearDB to host the MySQL databases. You cannot create a MySQL database directly from SQL Databases section. Finally, since we selected to create a new MySQL database we need to specify the database name and region in the last step. Also we need to accept the ClearDB’s terms as well. Then windows azure platform will download the WordPress codes and deploy the MySQL database and website. Then it will be ready to use. Select the website and click the BROWSE button, the WordPress administration page will be shown. After configured the WordPress here is my personal web blog on the cloud. It took me no more than 10 minutes to establish without any coding.   Monitor, Configure, Scale and Linked Resources Let’s click into the website I had just created in the portal and have a look on what we can do. In the website details page where are five sections. - Dashboard The overall information about this website, such as the basic usage status, public URL, compute mode, FTP address, subscription and links that we can specify the deployment credentials, TFS and Git publish setting, etc.. - Monitor Some status information such as the CPU usage, memory usage etc., errors, etc.. We can add more metrics by clicking the ADD METRICS button and the bottom as well. - Configure Here we can set the configurations of our website such as the .NET and PHP runtime version, diagnostics settings, application settings and the IIS default documents. - Scale This is something interesting. In WAWS there are two compute mode or called web site mode. One is “shared”, which means our website will be shared with other web sites in a group of windows azure virtual machines. Each web site have its own process (w3wp.exe) with some sandbox technology to isolate from others. When we need to scaling-out our web site in shared mode, we actually increased the working process count. Hence in shared mode we cannot specify the virtual machine size since they are shared across all web sites. This is a little bit different than the scaling mode of the cloud service (hosted service web role and worker role). The other mode called “dedicate”, which means our web site will use the whole windows azure virtual machine. This is the same hosting behavior as cloud service web role. In web role it will be deployed on the virtual machines we specified and all of them are only used by us. In web sites dedicate mode, it’s the same. In this mode when we scaling-out our web site we will use more virtual machines, and each of them will only host our own website. And we can specify the virtual machine size in this mode. In the developer portal we can select which mode we are using from the scale section. In shared mode we can only specify the instance count, but in dedicate mode we can specify the instance size as well as the instance count. - Linked Resource The MySQL database created alone with the creation of our WordPress web site is a linked resource. We can add more linked resources in this section.   Pricing For the web site itself, since this feature is in preview period if you are using shared mode, then you will get free up to 10 web sites. But if you are using dedicate mode, the price would be the virtual machines you are using. For example, if you are using dedicate and configured two middle size virtual machines then you will pay $230.40 per month. If there is SQL Database linked to your web site then they will be charged separately based on the Pay-As-You-Go price. For example a 1GB web edition database costs $9.99 per month. And the bandwidth will be charged as well. For example 10GB outbound data transfer costs $1.20 per month. For more information about the pricing please have a look at the windows azure pricing page.   Summary Windows Azure Web Sites gives us easier and quicker way to create, develop and deploy website to window azure platform. Comparing with the cloud service web role, the WAWS have many out-of-box gallery we can use directly. So if you just want to build a blog, CMS or business portal you don’t need to learn ASP.NET, you don’t need to learn how to configure DotNetNuke, you don’t need to learn how to prepare PHP and MySQL. By using WAWS gallery you can establish a website within 10 minutes without any lines of code. But in some cases we do need to code by ourselves. We may need to tweak the layout of our pages, or we may have a traditional ASP.NET or PHP web application which needed to migrated to the cloud. Besides the gallery WAWS also provides many features to download, upload code. It also provides the feature to integrate with some version control services such as TFS and Git. And it also provides the deploy approaches through FTP and Web Deploy. In the next post I will demonstrate how to use WebMatrix to download and modify the website, and how to use TFS and Git to deploy automatically one our code changes committed.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • Hosting and domain registrations for multiple clients under a single hosting account of mine?

    - by letseatfood
    I am finally getting regular work designing, developing, and deploying websites for small businesses and individuals. So far the websites utilize single-user content management systems, so the websites create, as far as I know, minimal load on the shared servers. I have always required that each of my clients purchase annual shared hosting at Dreamhost. For domain registration, I ask that they register with Dreamhost, but some already have a registered domain elsewhere and this is fine with me. I do this so the billing issues are the client's responsibility, not mine. My question is: Since I can register unlimited domains and connect them to my one shared hosting account at Dreamhost, should I not be requiring clients to individually pay for shared hosting and a domain? Should I actually be paying for one hosting account and then hosting all of my client's websites on that account? As I said before, I currently have each client buy their own hosting, because I feel that, for example, if there is high traffic to their site, there would be less a chance of the site going down than if their site was hosted with many others on one account. I am famous for being long-winded, please let me know if I can clarify at all. Thanks!

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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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  • Hosting and domain registrations for multiple clients

    - by letseatfood
    I am finally getting regular work desiging, developing, and deploying websites for small businesses and individuals. So far the websites utilize single-user content management systems, so the websites create, as far as I know, minimal load on the shared servers. I have always required that each of my clients purchase annual shared hosting at Dreamhost. For domain registration, I ask that they register with Dreamhost, but some already have a registered domain elsewhere and this is fine with me. I do this so the billing issues are the client's responsibility, not mine. My question is: Since I can register unlimited domains and connect them to my one shared hosting account at Dreamhost, should I not be requiring clients to individually pay for shared hosting and a domain? Should I actually be paying for one hosting account and then hosting all of my client's websites on that account? As I said before, I currently have each client buy their own hosting, because I feel that, for example, if there is high traffic to their site, there would be less a chance of the site going down than if their site was hosted with many others on one account. I am famous for being long-winded, please let me know if I can clarify at all. Thanks!

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  • Errors when installing updates

    - by user71613
    I am getting the following errors when installing updates. They started to appear after I upgraded my system to 12.04. Errors were encountered while processing: samba-common samba-common-bin samba grub-pc grub-gfxpayload-lists Setting up samba-common (2:3.6.3-2ubuntu2.2) ... perl: error while loading shared libraries: libperl.so.5.12: cannot open shared object file: No such file or directory dpkg: error processing samba-common (--configure): subprocess installed post-installation script returned error exit status 127 dpkg: dependency problems prevent configuration of samba-common-bin: samba-common-bin depends on samba-common (>= 2:3.4.0~pre1-2); however: Package samba-common is not configured yet. dpkg: error processing samba-common-bin (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of samba: samba depends on samba-common (= 2:3.6.3-2ubuntu2.2); however: Package samba-common is not configured yet. samba depends on samba-common-bin; however: Package samba-common-bin is not configured yet. dpkg: error processing samba (--configure): dependency problems - leaving unconfigured Setting up grub-gfxpayload-lists (0.6) ... Setting up grub-pc (1.99-21ubuntu3.1) ... perl: error while loading shared libraries: libperl.so.5.12: cannot open shared object file: No such file or directory dpkg: error processing grub-pc (--configure): subprocess installed post-installation script returned error exit status 127 Any ideas how to fix this?

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  • DLL Config in Mono

    - by nubela
    Hi, I'm trying to pick up Svn.NET (http://www.pumacode.org/projects/svndotnet/) library for use in my Mono project. I tried compiling its mockapp - svnmockapp project (http://www.pumacode.org/projects/svndotnet/browser/trunk/SvnMockApp) , I am able to get the references right and get it compiled right. I understand that it references 2 other modules libapr (libapr-1.so.0) and svn_client (libsvn_client-1.so.0) , by which I've created PumaCode.SvnDotNet.dll.config in /bin/Debug . That is all I've done to tried to try to get the mockapp at least outputting something to show that it is indeed interfacing SVN. Nevertheless, it is not working. Commands that are entered that doesn't interface SVN works fine: $ mono SvnTest.exe -usage Usage: SvnTest <subcommand> [options] Short Options: ~?.V Subcommands: add, checkout[co], status[st], update[up] For help on subcommands, use the -?/--help subcommand option. Commands that tries to access SVN throws an exception: $ mono SvnTest.exe st An exception was thrown by the type initializer for PumaCode.SvnDotNet.AprSharp.Apr Unhandled Exception: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object at PumaCode.SvnDotNet.SubversionSharp.SvnMockApp.CmdBase.Run (PumaCode.SvnDotNet.SubversionSharp.SvnMockApp.SubCommand sc, System.String[] args) [0x00000] at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (object,object[],System.Exception&) at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] --- End of inner exception stack trace --- at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] at PumaCode.SvnDotNet.SubversionSharp.SvnMockApp.Application.Run (System.String[] args) [0x00000] at PumaCode.SvnDotNet.SubversionSharp.SvnMockApp.Application.Main (System.String[] args) [0x00000] Using MONO_DEBUG_LEVEL="debug", we get the following log pasted here. At the tail end of the log, we see this: . . . Mono-INFO: DllImport attempting to load: 'libapr-1'. Mono-INFO: DllImport loading location: 'libapr-1.so'. Mono-INFO: DllImport error loading library: 'libapr-1.so: cannot open shared object file: No such file or directory'. Mono-INFO: DllImport loading library: './libapr-1.so'. Mono-INFO: DllImport error loading library './libapr-1.so: cannot open shared object file: No such file or directory'. Mono-INFO: DllImport loading: 'libapr-1'. Mono-INFO: DllImport error loading library 'libapr-1: cannot open shared object file: No such file or directory'. Mono-INFO: DllImport attempting to load: 'libapr-1'. Mono-INFO: DllImport loading location: 'libapr-1.so'. Mono-INFO: DllImport error loading library: 'libapr-1.so: cannot open shared object file: No such file or directory'. Mono-INFO: DllImport loading library: './libapr-1.so'. Mono-INFO: DllImport error loading library './libapr-1.so: cannot open shared object file: No such file or directory'. Mono-INFO: DllImport loading: 'libapr-1'. Mono-INFO: DllImport error loading library 'libapr-1: cannot open shared object file: No such file or directory'. Mono-INFO: DllImport attempting to load: 'libapr-1'. Mono-INFO: DllImport loading location: 'libapr-1.so'. Mono-INFO: DllImport error loading library: 'libapr-1.so: cannot open shared object file: No such file or directory'. Mono-INFO: DllImport loading library: './libapr-1.so'. Mono-INFO: DllImport error loading library './libapr-1.so: cannot open shared object file: No such file or directory'. Mono-INFO: DllImport loading: 'libapr-1'. Mono-INFO: DllImport error loading library 'libapr-1: cannot open shared object file: No such file or directory'. An exception was thrown by the type initializer for PumaCode.SvnDotNet.AprSharp.Apr I've tried to symlink the appropriate modules in the directory where SvnTest.exe exists, but this still persist. How can I fix this? Did I place the PumaCode.SvnDotNet.dll.config in the wrong folder? (I placed it at /bin/Debug and also tried /bin) What can I do to remedy this? Thank you for your kind help! Much appreciated! Heres the config file: (PumaCode.SvnDotNet.dll.config) <configuration> <dllmap dll="libapr" target="/usr/lib/libapr-1.so.0"/> <dllmap dll="svn_client-1" target="/usr/lib/libsvn_client-1.so.0"/> </configuration>

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  • How to handle failure to release a resource which is contained in a smart pointer?

    - by cj
    How should an error during resource deallocation be handled, when the object representing the resource is contained in a shared pointer? Smart pointers are a useful tool to manage resources safely. Examples of such resources are memory, disk files, database connections, or network connections. // open a connection to the local HTTP port boost::shared_ptr<Socket> socket = Socket::connect("localhost:80"); In a typical scenario, the class encapsulating the resource should be noncopyable and polymorphic. A good way to support this is to provide a factory method returning a shared pointer, and declare all constructors non-public. The shared pointers can now be copied from and assigned to freely. The object is automatically destroyed when no reference to it remains, and the destructor then releases the resource. /** A TCP/IP connection. */ class Socket { public: static boost::shared_ptr<Socket> connect(const std::string& address); virtual ~Socket(); protected: Socket(const std::string& address); private: // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; But there is a problem with this approach. The destructor must not throw, so a failure to release the resource will remain undetected. A common way out of this problem is to add a public method to release the resource. class Socket { public: virtual void close(); // may throw // ... }; Unfortunately, this approach introduces another problem: Our objects may now contain resources which have already been released. This complicates the implementation of the resource class. Even worse, it makes it possible for clients of the class to use it incorrectly. The following example may seem far-fetched, but it is a common pitfall in multi-threaded code. socket->close(); // ... size_t nread = socket->read(&buffer[0], buffer.size()); // wrong use! Either we ensure that the resource is not released before the object is destroyed, thereby losing any way to deal with a failed resource deallocation. Or we provide a way to release the resource explicitly during the object's lifetime, thereby making it possible to use the resource class incorrectly. There is a way out of this dilemma. But the solution involves using a modified shared pointer class. These modifications are likely to be controversial. Typical shared pointer implementations, such as boost::shared_ptr, require that no exception be thrown when their object's destructor is called. Generally, no destructor should ever throw, so this is a reasonable requirement. These implementations also allow a custom deleter function to be specified, which is called in lieu of the destructor when no reference to the object remains. The no-throw requirement is extended to this custom deleter function. The rationale for this requirement is clear: The shared pointer's destructor must not throw. If the deleter function does not throw, nor will the shared pointer's destructor. However, the same holds for other member functions of the shared pointer which lead to resource deallocation, e.g. reset(): If resource deallocation fails, no exception can be thrown. The solution proposed here is to allow custom deleter functions to throw. This means that the modified shared pointer's destructor must catch exceptions thrown by the deleter function. On the other hand, member functions other than the destructor, e.g. reset(), shall not catch exceptions of the deleter function (and their implementation becomes somewhat more complicated). Here is the original example, using a throwing deleter function: /** A TCP/IP connection. */ class Socket { public: static SharedPtr<Socket> connect(const std::string& address); protected: Socket(const std::string& address); virtual Socket() { } private: struct Deleter; // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; struct Socket::Deleter { void operator()(Socket* socket) { // Close the connection. If an error occurs, delete the socket // and throw an exception. delete socket; } }; SharedPtr<Socket> Socket::connect(const std::string& address) { return SharedPtr<Socket>(new Socket(address), Deleter()); } We can now use reset() to free the resource explicitly. If there is still a reference to the resource in another thread or another part of the program, calling reset() will only decrement the reference count. If this is the last reference to the resource, the resource is released. If resource deallocation fails, an exception is thrown. SharedPtr<Socket> socket = Socket::connect("localhost:80"); // ... socket.reset();

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  • Updating Cisco VPN config to add vpnc support

    - by Igor Kuzmitshov
    I have a Cisco 1841 configured for VPN connections of two types: Peer-to-peer for partners' routers (IPsec) — using different crypto isakmp key and crypto map with set peer, set transform-set, match address for every peer (same map name, different priorities). That crypto map name is added to the WAN interface. Client access (PPTP) — using vpdn-group with accept-dialin protocol pptp. Now, a new partner wants to connect using vpnc client. The latter needs IPSec ID (group name) and IPSec secret in addition to username and password. I guess that IPSec secret is pre-shared key that can be specified in crypto isakmp key on Cisco. But I could not find any VPN tutorials involving groups. Hence, my questions: How to add IPSec ID (group name) and IPSec secret on Cisco router for vpnc connections? Should I add a new crypto map matching all addresses as well? Is it possible to add this configuration without breaking the existing setup? Thank you.

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  • Postfix - exclude messages with specific header values from relayhost?

    - by Kyle MacFarlane
    Starting with the following basic configuration to relay all messages in Postfix to PostMarkApp.com: #start postmarkapps settings smtp_sasl_auth_enable = yes smtp_sasl_password_maps = static:secret:secret (where "secret is your API key") smtp_sasl_security_options = noanonymous relayhost = [smtp.postmarkapp.com]:25 #end postmarkapp settings The problem with this is if for example something starts spitting our error messages they will all go through PostMark and cost money. One way to bypass relayhost is to setup sender_dependent_relayhost_maps and have certain addresses map back to yourdomain.com. But this doesn't work in web apps where all messages are sent by the same user but with varying From headers. So how can I achieve the same effect as sender_dependent_relayhost_maps but looking at the From or Subject headers instead of merely the user?

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  • php cookie not working

    - by Jacksta
    I am trying to use a cookie with authentication. This page works once entering user and pass <? if ((!$_POST[username]) || (!$_POST[password])) { header("Location: show_login.html"); exit; } $db_name = "testDB"; $table_name = "auth_users"; $connection = @mysql_connect("localhost", "user", "pass") or die(mysql_error()); $db = @mysql_select_db($db_name, $connection) or die(mysql_error()); $sql = "SELECT * FROM $table_name WHERE username ='$_POST[username]' AND password = password('$_POST[password]')"; $result = @mysql_query($sql, $connection) or die(mysql_error()); $num = mysql_num_rows($result); if ($num != 0) { $cookie_name = "auth"; $cookie_value = "ok"; $cookie_expire = "0"; $cookie_domain = "domain.com.au"; setcookie($cookie_name, $cookis_value, $cookie_expire, "/", $cookie_domain, 0); $display_block = " <p><strong>Secret Menu:</strong></p> <ul> <li><a href=\"secretA.php\">secret page A</a> <li><a href=\"secretB.php\">secret page B</a> </ul>"; } else { header("Location: show_login.html"); exit; } ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Secret Area</title> </head> <body> <? echo "$display_block"; ?> </body> </html> WHen clicking on either secretA.php or secretB.php I am redirected to log in again, it should work. here is the code. secretB.php <?php if ($_COOKIE[auth] == "ok") { $msg = "<p>Welcome to secret page B, authorised user! </P>"; } else { header( "Location: /show_login.html"); exit; } ?> <HTML> <HEAD> <title>Secret Page B:</title> </HEAD> <BODY> <? echo "$msg"; ?> </BODY> </HTML>

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  • Ada and 'The Book'

    - by Phil Factor
    The long friendship between Charles Babbage and Ada Lovelace created one of the most exciting and mysterious of collaborations ever to have resulted in a technological breakthrough. The fireworks that created by the collision of two prodigious mathematical and creative talents resulted in an invention, the Analytical Engine, which went on to change society fundamentally. However, beyond that, we just don't know what the bulk of their collaborative work was about:;  it was done in strictest secrecy. Even the known outcome of their friendship, the first programmable computer, was shrouded in mystery. At the time, nobody, except close friends and family, had any idea of Ada Byron's contribution to the invention of the ‘Engine’, and how to program it. Her great insight was published in August 1843, under the initials AAL, standing for Ada Augusta Lovelace, her title then being the Countess of Lovelace. It was contained in a lengthy ‘note’ to her translation of a publication that remains the best description of Babbage's amazing Analytical Engine. The secret identity of the person behind those enigmatic initials was finally revealed by Prince de Polignac who, seventy years later, wrote to Ada's daughter to seek confirmation that her mother had, indeed, been the author of the brilliant sentences that described so accurately how Babbage's mechanical computer could be programmed with punch-cards. L.F. Menabrea's paper on the Analytical Engine first appeared in the 'Bibliotheque Universelle de Geneve' in October 1842, and Ada translated it anonymously for Taylor's 'Scientific Memoirs'. Charles Babbage was surprised that she had not written an original paper as she already knew a surprising amount about the way the machine worked. He persuaded her to at least write some explanatory notes. These notes ended up extending to four times the length of the original article and represented the first published account of how a machine could be programmed to perform any calculation. Her example of programming the Bernoulli sequence would have worked on the Analytical engine had the device’s construction been completed, and gave Ada an unassailable claim to have invented the art of programming. What was the reason for Ada's secrecy? She was the only legitimate child of Lord Byron, who was probably the best known celebrity of the age, so she was already famous. She was a senior aristocrat, with titles, a fortune in money and vast estates in the Midlands. She had political influence, and was the cousin of Lord Melbourne, who was the Prime Minister at that time. She was friendly with the young Queen Victoria. Her mathematical activities were a pastime, and not one that would be considered by others to be in keeping with her roles and responsibilities. You wouldn't dare to dream up a fictional heroine like Ada. She was dazzlingly beautiful and talented. She could speak several languages fluently, and play some musical instruments with professional skill. Contemporary accounts refer to her being 'accomplished in science, art and literature'. On top of that, she was a brilliant mathematician, a talent inherited from her mother, Annabella Milbanke. In her mother's circle of literary and scientific friends was Charles Babbage, and Ada's friendship with him dates from her teenage zest for Mathematics. She was one of the first people he'd ever met who understood what he had attempted to achieve with the 'Difference Engine', and with whom he could converse as intellectual equals. He arranged for her to have an education from the most talented academics in the country. Ada melted the heart of the cantankerous genius to the point that he became a faithful and loyal father-figure to her. She was one of the very few who could grasp the principles of the later, and very different, ‘Analytical Engine’ which was designed from the start to tackle a variety of tasks. Sadly, Ada Byron's life ended less than a decade after completing the work that assured her long-term fame, in November 1852. She was dying of cancer, her gambling habits had caused her to run up huge debts, she'd had more than one affairs, and she was being blackmailed. Her brilliant but unempathic mother was nursing her in her final illness, destroying her personal letters and records, and repaying her debts. Her husband was distraught but helpless. Charles Babbage, however, maintained his steadfast paternalistic friendship to the end. She appointed her loyal friend to be her executor. For years, she and Babbage had been working together on a secret project, known only as 'The Book'. We have a clue to what it was in a letter written by her nine years earlier, on 11th August 1843. It was a joint project by herself and Lord Lovelace, her husband, and was intended to involve Babbage's 'undivided energies'. It involved 'consulting your Engine' (it required Babbage’s computer). The letter gives no hint about the project except for the high-minded nature of its purpose, and its highly mathematical nature.  From then on, the surviving correspondence between the two gives only veiled references to 'The Book'. There isn't much, since Babbage later destroyed any letters that could have damaged her reputation within the Establishment. 'I cannot spare the book today, which I am very sorry for. At the moment I want it for constant reference, but I think you can have it tomorrow' (Oct 1844)  And 'I will send you the book directly, and you can say, when you receive it, how long you will want to keep it'. (Nov 1844)  The two of them were obviously intent on the work: She writes, four years later, 'I have an engagement for Wednesday which will prevent me from attending to your wishes about the book' (Dec 1848). This was something that they both needed to work on, but could not do in parallel: 'I will send the book on Tuesday, and it can be left with you till Friday' (11 Feb 1849). After six years work, it had been so well-handled that it was beginning to fall apart: 'Don't forget the new cover you promised for the book. The poor book is very shabby and wants one' (20 Sept 1849). So what was going on? The word 'book' was not a code-word: it was a real book, probably a 'printer's blank', plain paper, but properly bound so printers and publishers could show off how the published work might look. The hints from the correspondence are of advanced mathematics. It is obvious that the book was travelling between them, back and forth, each one working on it for less than a week before passing it back. Ada and her husband were certainly involved in gambling large sums of money on the horses, and so most biographers have concluded that the three of them were trying to calculate the mathematical odds on the horses. This theory has three large problems. Firstly, Ada's original letter proposing the project refers to its high-minded nature. Babbage was temperamentally opposed to gambling and would scarcely have given so much time to the project, even though he was devoted to Ada. Secondly, Babbage would have very soon have realized the hopelessness of trying to beat the bookies. This sort of betting never attracts his type of intellectual background. The third problem is that any work on calculating the odds on horses would not need a well-thumbed book to pass back and forth between them; they would have not had to work in series. The original project was instigated by Ada, along with her husband, William King-Noel, 1st Earl of Lovelace. Charles Babbage was invited to join the project after the couple had come up with the idea. What could William have contributed? One might assume that William was a Bertie Wooster character, addicted only to the joys of the turf, but this was far from the truth. He was a scientist, a Cambridge graduate who was later elected to be a Fellow of the Royal Society. After Eton, he went to Trinity College, Cambridge. On graduation, he entered the diplomatic service and acted as secretary under Lord Nugent, who was Lord Commissioner of the Ionian Islands. William was very friendly with Babbage too, able to discuss scientific matters on equal terms. He was a capable engineer who invented a process for bending large timbers by the application of steam heat. He delivered a paper to the Institution of Civil Engineers in 1849, and received praise from the great engineer, Isambard Kingdom Brunel. As well as being Lord Lieutenant of the County of Surrey for most of Victoria's reign, he had time for a string of scientific and engineering achievements. Whatever the project was, it is unlikely that William was a junior partner. After Ada's death, the project disappeared. Then, two years later, Babbage, through one of his occasional outbursts of temper, demonstrated that he was able to decrypt one of the most powerful of secret codes, Vigenère's autokey cipher.  All contemporary diplomatic and military messages used a variant of this cipher. Babbage had made three important discoveries, namely, the mathematical law of this cipher, the principle of the key periodicity, and the technique of the symmetry of position. The technique is now known as the Kasiski examination, also called the Kasiski test, but Babbage got there first. At one time, he listed amongst his future projects, the writing of a book 'The Philosophy of Decyphering', but it never came to anything. This discovery was going to change the course of history, since it was used to decipher the Russians’ military dispatches in the Crimean war. Babbage himself played a role during the Crimean War as a cryptographical adviser to his friend, Rear-Admiral Sir Francis Beaufort of the Admiralty. This is as much as we can be certain about in trying to make sense of the bulk of the time that Charles Babbage and Ada Lovelace worked together. Nine years of intensive work, involving the 'Engine' and a great deal of mathematics and research seems to have been lost: or has it? I've argued in the past http://www.simple-talk.com/community/blogs/philfactor/archive/2008/06/13/59614.aspx that the cracking of the Vigenère autokey cipher, was a fundamental motive behind the British Government's support and funding of the 'Difference Engine'. The Duke of Wellington, whose understanding of the military significance of being able to read enemy dispatches, was the most steadfast advocate of the project. If the three friends were actually doing the work of cracking codes by mathematical techniques that used the techniques of key periodicity, and symmetry of position (the use of a book being passed quickly to and fro is very suggestive), intending to then use the 'Engine' to do the routine cracking of each dispatch, then this is a rather different story. The project was Ada and William's idea. (William had served in the diplomatic service and would be familiar with the use of codes). This makes Ada Lovelace the initiator of a project which, by giving both Britain, and probably the USA, a diplomatic and military advantage in the second part of the Nineteenth century, changed world history. Ada would never have wanted any credit for cracking the cipher, and developing the method that rendered all contemporary military and diplomatic ciphering techniques nugatory; quite the reverse. And it is clear from the gaps in the record of the letters between the collaborators that the evidence was destroyed, probably on her request by her irascible but intensely honorable executor, Charles Babbage. Charles Babbage toyed with the idea of going public, but the Crimean war put an end to that. The British Government had a valuable secret, and intended to keep it that way. Ada and Charles had quite often discussed possible moneymaking projects that would fund the development of the Analytic Engine, the first programmable computer, but their secret work was never in the running as a potential cash cow. I suspect that the British Government was, even then, working on the concealment of a discovery whose value to the nation depended on it remaining so. The success of code-breaking in the Crimean war, and the American Civil war, led to the British and Americans  subsequently giving much more weight and funding to the science of decryption. Paradoxically, this makes Ada's contribution even closer to the creation of Colossus, the first digital computer, at Bletchley Park, specifically to crack the Nazi’s secret codes.

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  • "ldap_add: Naming violation (64)" error when configuring OpenLDAP

    - by user3215
    I am following the Ubuntu server guide to configure OpenLDAP on an Ubuntu 10.04 server, but can not get it to work. When I try to use sudo ldapadd -x -D cn=admin,dc=don,dc=com -W -f frontend.ldif I'm getting the following error: Enter LDAP Password: <entered 'secret' as password> adding new entry "dc=don,dc=com" ldap_add: Naming violation (64) additional info: value of single-valued naming attribute 'dc' conflicts with value present in entry Again when I try to do the same, I'm getting the following error: root@avy-desktop:/home/avy# sudo ldapadd -x -D cn=admin,dc=don,dc=com -W -f frontend.ldif Enter LDAP Password: ldap_bind: Invalid credentials (49) Here is the backend.ldif file: # Load dynamic backend modules dn: cn=module,cn=config objectClass: olcModuleList cn: module olcModulepath: /usr/lib/ldap olcModuleload: back_hdb # Database settings dn: olcDatabase=hdb,cn=config objectClass: olcDatabaseConfig objectClass: olcHdbConfig olcDatabase: {1}hdb olcSuffix: dc=don,dc=com olcDbDirectory: /var/lib/ldap olcRootDN: cn=admin,dc=don,dc=com olcRootPW: secret olcDbConfig: set_cachesize 0 2097152 0 olcDbConfig: set_lk_max_objects 1500 olcDbConfig: set_lk_max_locks 1500 olcDbConfig: set_lk_max_lockers 1500 olcDbIndex: objectClass eq olcLastMod: TRUE olcDbCheckpoint: 512 30 olcAccess: to attrs=userPassword by dn="cn=admin,dc=don,dc=com" write by anonymous auth by self write by * none olcAccess: to attrs=shadowLastChange by self write by * read olcAccess: to dn.base="" by * read olcAccess: to * by dn="cn=admin,dc=don,dc=com" write by * read frontend.ldif file: # Create top-level object in domain dn: dc=don,dc=com objectClass: top objectClass: dcObject objectclass: organization o: Example Organization dc: Example description: LDAP Example # Admin user. dn: cn=admin,dc=don,dc=com objectClass: simpleSecurityObject objectClass: organizationalRole cn: admin description: LDAP administrator userPassword: secret dn: ou=people,dc=don,dc=com objectClass: organizationalUnit ou: people dn: ou=groups,dc=don,dc=com objectClass: organizationalUnit ou: groups dn: uid=john,ou=people,dc=don,dc=com objectClass: inetOrgPerson objectClass: posixAccount objectClass: shadowAccount uid: john sn: Doe givenName: John cn: John Doe displayName: John Doe uidNumber: 1000 gidNumber: 10000 userPassword: password gecos: John Doe loginShell: /bin/bash homeDirectory: /home/john shadowExpire: -1 shadowFlag: 0 shadowWarning: 7 shadowMin: 8 shadowMax: 999999 shadowLastChange: 10877 mail: [email protected] postalCode: 31000 l: Toulouse o: Example mobile: +33 (0)6 xx xx xx xx homePhone: +33 (0)5 xx xx xx xx title: System Administrator postalAddress: initials: JD dn: cn=example,ou=groups,dc=don,dc=com objectClass: posixGroup cn: example gidNumber: 10000 Can anyone help me?

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  • How to Configure OpenLDAP on Ubuntu 10.04 Server

    - by user3215
    I am following the Ubuntu server guide to configure OpenLDAP on an Ubuntu 10.04 server, but can not get it to work. When I try to use sudo ldapadd -x -D cn=admin,dc=don,dc=com -W -f frontend.ldif I'm getting the following error: Enter LDAP Password: <entered 'secret' as password> adding new entry "dc=don,dc=com" ldap_add: Naming violation (64) additional info: value of single-valued naming attribute 'dc' conflicts with value present in entry Again when I try to do the same, I'm getting the following error: root@avy-desktop:/home/avy# sudo ldapadd -x -D cn=admin,dc=don,dc=com -W -f frontend.ldif Enter LDAP Password: ldap_bind: Invalid credentials (49) Here is the backend.ldif file: # Load dynamic backend modules dn: cn=module,cn=config objectClass: olcModuleList cn: module olcModulepath: /usr/lib/ldap olcModuleload: back_hdb # Database settings dn: olcDatabase=hdb,cn=config objectClass: olcDatabaseConfig objectClass: olcHdbConfig olcDatabase: {1}hdb olcSuffix: dc=don,dc=com olcDbDirectory: /var/lib/ldap olcRootDN: cn=admin,dc=don,dc=com olcRootPW: secret olcDbConfig: set_cachesize 0 2097152 0 olcDbConfig: set_lk_max_objects 1500 olcDbConfig: set_lk_max_locks 1500 olcDbConfig: set_lk_max_lockers 1500 olcDbIndex: objectClass eq olcLastMod: TRUE olcDbCheckpoint: 512 30 olcAccess: to attrs=userPassword by dn="cn=admin,dc=don,dc=com" write by anonymous auth by self write by * none olcAccess: to attrs=shadowLastChange by self write by * read olcAccess: to dn.base="" by * read olcAccess: to * by dn="cn=admin,dc=don,dc=com" write by * read frontend.ldif file: # Create top-level object in domain dn: dc=don,dc=com objectClass: top objectClass: dcObject objectclass: organization o: Example Organization dc: Example description: LDAP Example # Admin user. dn: cn=admin,dc=don,dc=com objectClass: simpleSecurityObject objectClass: organizationalRole cn: admin description: LDAP administrator userPassword: secret dn: ou=people,dc=don,dc=com objectClass: organizationalUnit ou: people dn: ou=groups,dc=don,dc=com objectClass: organizationalUnit ou: groups dn: uid=john,ou=people,dc=don,dc=com objectClass: inetOrgPerson objectClass: posixAccount objectClass: shadowAccount uid: john sn: Doe givenName: John cn: John Doe displayName: John Doe uidNumber: 1000 gidNumber: 10000 userPassword: password gecos: John Doe loginShell: /bin/bash homeDirectory: /home/john shadowExpire: -1 shadowFlag: 0 shadowWarning: 7 shadowMin: 8 shadowMax: 999999 shadowLastChange: 10877 mail: [email protected] postalCode: 31000 l: Toulouse o: Example mobile: +33 (0)6 xx xx xx xx homePhone: +33 (0)5 xx xx xx xx title: System Administrator postalAddress: initials: JD dn: cn=example,ou=groups,dc=don,dc=com objectClass: posixGroup cn: example gidNumber: 10000 Can anyone help me?

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  • How to configure ldap on ubuntu 10.04 server

    - by user3215
    I am following the link to configure ldap on ubuntu 10.04 server but could not. when I try to use sudo ldapadd -x -D cn=admin,dc=don,dc=com -W -f frontend.ldif I'm getting the following error: Enter LDAP Password: <entered 'secret' as password> adding new entry "dc=don,dc=com" ldap_add: Naming violation (64) additional info: value of single-valued naming attribute 'dc' conflicts with value present in entry Again when I try to do the same, I'm getting the following error: root@avy-desktop:/home/avy# sudo ldapadd -x -D cn=admin,dc=don,dc=com -W -f frontend.ldif Enter LDAP Password: ldap_bind: Invalid credentials (49) Here is the backend.ldif file # Load dynamic backend modules dn: cn=module,cn=config objectClass: olcModuleList cn: module olcModulepath: /usr/lib/ldap olcModuleload: back_hdb # Database settings dn: olcDatabase=hdb,cn=config objectClass: olcDatabaseConfig objectClass: olcHdbConfig olcDatabase: {1}hdb olcSuffix: dc=don,dc=com olcDbDirectory: /var/lib/ldap olcRootDN: cn=admin,dc=don,dc=com olcRootPW: secret olcDbConfig: set_cachesize 0 2097152 0 olcDbConfig: set_lk_max_objects 1500 olcDbConfig: set_lk_max_locks 1500 olcDbConfig: set_lk_max_lockers 1500 olcDbIndex: objectClass eq olcLastMod: TRUE olcDbCheckpoint: 512 30 olcAccess: to attrs=userPassword by dn="cn=admin,dc=don,dc=com" write by anonymous auth by self write by * none olcAccess: to attrs=shadowLastChange by self write by * read olcAccess: to dn.base="" by * read olcAccess: to * by dn="cn=admin,dc=don,dc=com" write by * read frontend.ldif file: # Create top-level object in domain dn: dc=don,dc=com objectClass: top objectClass: dcObject objectclass: organization o: Example Organization dc: Example description: LDAP Example # Admin user. dn: cn=admin,dc=don,dc=com objectClass: simpleSecurityObject objectClass: organizationalRole cn: admin description: LDAP administrator userPassword: secret dn: ou=people,dc=don,dc=com objectClass: organizationalUnit ou: people dn: ou=groups,dc=don,dc=com objectClass: organizationalUnit ou: groups dn: uid=john,ou=people,dc=don,dc=com objectClass: inetOrgPerson objectClass: posixAccount objectClass: shadowAccount uid: john sn: Doe givenName: John cn: John Doe displayName: John Doe uidNumber: 1000 gidNumber: 10000 userPassword: password gecos: John Doe loginShell: /bin/bash homeDirectory: /home/john shadowExpire: -1 shadowFlag: 0 shadowWarning: 7 shadowMin: 8 shadowMax: 999999 shadowLastChange: 10877 mail: [email protected] postalCode: 31000 l: Toulouse o: Example mobile: +33 (0)6 xx xx xx xx homePhone: +33 (0)5 xx xx xx xx title: System Administrator postalAddress: initials: JD dn: cn=example,ou=groups,dc=don,dc=com objectClass: posixGroup cn: example gidNumber: 10000 Anybody could help me?

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  • Where to Perform Authentication in REST API Server?

    - by David V
    I am working on a set of REST APIs that needs to be secured so that only authenticated calls will be performed. There will be multiple web apps to service these APIs. Is there a best-practice approach as to where the authentication should occur? I have thought of two possible places. Have each web app perform the authentication by using a shared authentication service. This seems to be in line with tools like Spring Security, which is configured at the web app level. Protect each web app with a "gateway" for security. In this approach, the web app never receives unauthenticated calls. This seems to be the approach of Apache HTTP Server Authentication. With this approach, would you use Apache or nginx to protect it, or something else in between Apache/nginx and your web app? For additional reference, the authentication is similar to services like AWS that have a non-secret identifier combined with a shared secret key. I am also considering using HMAC. Also, we are writing the web services in Java using Spring. Update: To clarify, each request needs to be authenticated with the identifier and secret key. This is similar to how AWS REST requests work.

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  • Why lock-free data structures just aren't lock-free enough

    - by Alex.Davies
    Today's post will explore why the current ways to communicate between threads don't scale, and show you a possible way to build scalable parallel programming on top of shared memory. The problem with shared memory Soon, we will have dozens, hundreds and then millions of cores in our computers. It's inevitable, because individual cores just can't get much faster. At some point, that's going to mean that we have to rethink our architecture entirely, as millions of cores can't all access a shared memory space efficiently. But millions of cores are still a long way off, and in the meantime we'll see machines with dozens of cores, struggling with shared memory. Alex's tip: The best way for an application to make use of that increasing parallel power is to use a concurrency model like actors, that deals with synchronisation issues for you. Then, the maintainer of the actors framework can find the most efficient way to coordinate access to shared memory to allow your actors to pass messages to each other efficiently. At the moment, NAct uses the .NET thread pool and a few locks to marshal messages. It works well on dual and quad core machines, but it won't scale to more cores. Every time we use a lock, our core performs an atomic memory operation (eg. CAS) on a cell of memory representing the lock, so it's sure that no other core can possibly have that lock. This is very fast when the lock isn't contended, but we need to notify all the other cores, in case they held the cell of memory in a cache. As the number of cores increases, the total cost of a lock increases linearly. A lot of work has been done on "lock-free" data structures, which avoid locks by using atomic memory operations directly. These give fairly dramatic performance improvements, particularly on systems with a few (2 to 4) cores. The .NET 4 concurrent collections in System.Collections.Concurrent are mostly lock-free. However, lock-free data structures still don't scale indefinitely, because any use of an atomic memory operation still involves every core in the system. A sync-free data structure Some concurrent data structures are possible to write in a completely synchronization-free way, without using any atomic memory operations. One useful example is a single producer, single consumer (SPSC) queue. It's easy to write a sync-free fixed size SPSC queue using a circular buffer*. Slightly trickier is a queue that grows as needed. You can use a linked list to represent the queue, but if you leave the nodes to be garbage collected once you're done with them, the GC will need to involve all the cores in collecting the finished nodes. Instead, I've implemented a proof of concept inspired by this intel article which reuses the nodes by putting them in a second queue to send back to the producer. * In all these cases, you need to use memory barriers correctly, but these are local to a core, so don't have the same scalability problems as atomic memory operations. Performance tests I tried benchmarking my SPSC queue against the .NET ConcurrentQueue, and against a standard Queue protected by locks. In some ways, this isn't a fair comparison, because both of these support multiple producers and multiple consumers, but I'll come to that later. I started on my dual-core laptop, running a simple test that had one thread producing 64 bit integers, and another consuming them, to measure the pure overhead of the queue. So, nothing very interesting here. Both concurrent collections perform better than the lock-based one as expected, but there's not a lot to choose between the ConcurrentQueue and my SPSC queue. I was a little disappointed, but then, the .NET Framework team spent a lot longer optimising it than I did. So I dug out a more powerful machine that Red Gate's DBA tools team had been using for testing. It is a 6 core Intel i7 machine with hyperthreading, adding up to 12 logical cores. Now the results get more interesting. As I increased the number of producer-consumer pairs to 6 (to saturate all 12 logical cores), the locking approach was slow, and got even slower, as you'd expect. What I didn't expect to be so clear was the drop-off in performance of the lock-free ConcurrentQueue. I could see the machine only using about 20% of available CPU cycles when it should have been saturated. My interpretation is that as all the cores used atomic memory operations to safely access the queue, they ended up spending most of the time notifying each other about cache lines that need invalidating. The sync-free approach scaled perfectly, despite still working via shared memory, which after all, should still be a bottleneck. I can't quite believe that the results are so clear, so if you can think of any other effects that might cause them, please comment! Obviously, this benchmark isn't realistic because we're only measuring the overhead of the queue. Any real workload, even on a machine with 12 cores, would dwarf the overhead, and there'd be no point worrying about this effect. But would that be true on a machine with 100 cores? Still to be solved. The trouble is, you can't build many concurrent algorithms using only an SPSC queue to communicate. In particular, I can't see a way to build something as general purpose as actors on top of just SPSC queues. Fundamentally, an actor needs to be able to receive messages from multiple other actors, which seems to need an MPSC queue. I've been thinking about ways to build a sync-free MPSC queue out of multiple SPSC queues and some kind of sign-up mechanism. Hopefully I'll have something to tell you about soon, but leave a comment if you have any ideas.

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  • How to Share Files Between User Accounts on Windows, Linux, or OS X

    - by Chris Hoffman
    Your operating system provides each user account with its own folders when you set up several different user accounts on the same computer. Shared folders allow you to share files between user accounts. This process works similarly on Windows, Linux, and Mac OS X. These are all powerful multi-user operating systems with similar folder and file permission systems. Windows On Windows, the “Public” user’s folders are accessible to all users. You’ll find this folder under C:\Users\Public by default. Files you place in any of these folders will be accessible to other users, so it’s a good way to share music, videos, and other types of files between users on the same computer. Windows even adds these folders to each user’s libraries by default. For example, a user’s Music library contains the user’s music folder under C:\Users\NAME\as well as the public music folder under C:\Users\Public\. This makes it easy for each user to find the shared, public files. It also makes it easy to make a file public — just drag and drop a file from the user-specific folder to the public folder in the library. Libraries are hidden by default on Windows 8.1, so you’ll have to unhide them to do this. These Public folders can also be used to share folders publically on the local network. You’ll find the Public folder sharing option under Advanced sharing settings in the Network and Sharing Control Panel. You could also choose to make any folder shared between users, but this will require messing with folder permissions in Windows. To do this, right-click a folder anywhere in the file system and select Properties. Use the options on the Security tab to change the folder’s permissions and make it accessible to different user accounts. You’ll need administrator access to do this. Linux This is a bit more complicated on Linux, as typical Linux distributions don’t come with a special user folder all users have read-write access to. The Public folder on Ubuntu is for sharing files between computers on a network. You can use Linux’s permissions system to give other user accounts read or read-write access to specific folders. The process below is for Ubuntu 14.04, but it should be identical on any other Linux distribution using GNOME with the Nautilus file manager. It should be similar for other desktop environments, too. Locate the folder you want to make accessible to other users, right-click it, and select Properties. On the Permissions tab, give “Others” the “Create and delete files” permission. Click the Change Permissions for Enclosed Files button and give “Others” the “Read and write” and “Create and Delete Files” permissions. Other users on the same computer will then have read and write access to your folder. They’ll find it under /home/YOURNAME/folder under Computer. To speed things up, they can create a link or bookmark to the folder so they always have easy access to it. Mac OS X Mac OS X creates a special Shared folder that all user accounts have access to. This folder is intended for sharing files between different user accounts. It’s located at /Users/Shared. To access it, open the Finder and click Go > Computer. Navigate to Macintosh HD > Users > Shared. Files you place in this folder can be accessed by any user account on your Mac. These tricks are useful if you’re sharing a computer with other people and you all have your own user accounts — maybe your kids have their own limited accounts. You can share a music library, downloads folder, picture archive, videos, documents, or anything else you like without keeping duplicate copies.

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