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  • Are there any programming languages targeting PHP, besides haXe?

    - by stesch
    PHP doesn't get much love but is still a winner at easy deployment (for cheap hosting). Are there any programming languages (besides haXe) that target PHP? Writing applications in this language and then translating it into PHP, like some languages target C as an intermediate language? The Scheme implementation Chicken compiles into C. XOTcl converts Java code into Tcl code LINJ was(?) a tool to convert Lisp into nice looking Java code … + a lot of ways to produce JavaScript without touching JavaScript.

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  • Is there a good reason Uni courses still use "academic" languages like modula2?

    - by Cheeso
    This question prompts me to ask - why do universities still teach in languages like Modula2, when improved modern languages are available for free? Are there uni's that still teach Pascal, for example? I mean, it was good 30 years ago, but... now? Why? Why not Java, C#, Haskell? Related: Is it backwards to still teach LISP? Is this a duplicate question? If not, I think it ought to be a community wiki topic.

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  • Interview question: difference between object and object-oriented languages.

    - by Bar
    My friend was asked the following question: what's the difference between object language and object-oriented language? It's a little unintelligible question. What does term «object language» correspond to? Does that mean «pure» object-oriented language, like the Wikipedia article says: Languages called "pure" OO languages, because everything in them is treated consistently as an object, from primitives such as characters and punctuation, all the way up to whole classes, prototypes, blocks, modules, etc. They were designed specifically to facilitate, even enforce, OO methods. Examples: Smalltalk, Eiffel, Ruby, JADE, VB.NET.

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  • should a student be diversifying or mastering programming languages?

    - by Max Link
    As the question states, is it better if a student diversifies or explores when learning programming languages or should they focus only on 2-3 languages and really get to know them well? Example of what I mean by diversifying: Functional -> Scheme Procedural -> C Object Oriented -> Java Dynamic or scripting -> Python Other -> C++ I have a few breaks in between semesters sometimes (up to 3 months) and I'm thinking of either learning a new language or "master" those that I know right now. Which would benefit me in the future? I know some(about 3 months of self studying each) Java, C, and C++ already . If I'm not mistaken, where I live, the industry is heavy on Java, C++, and C#.

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  • Rename Applications and Virtual Directories in IIS7

    - by AngelEyes
    from http://lanitdev.wordpress.com/2010/09/02/rename-applications-and-virtual-directories-in-iis7/   Rename Applications and Virtual Directories in IIS7 September 2, 2010 — Brian Grinstead Have you ever wondered why the box to change the name or “Alias” on an application or virtual directory is greyed out (see screenshot below)? I found a way to change the name without recreating all your settings. It uses the built in administration commands in IIS7, called appcmd. Renaming Applications In IIS7 Open a command prompt to see all of your applications. 1 C:> %systemroot%\system32\inetsrv\appcmd list app 2   3     APP "Default Web Site/OldApplicationName" 4     APP "Default Web Site/AnotherApplication" Run a command like this to change your “OldApplicationName” path to “NewApplicationName”. Now you can use http://localhost/newapplicationname 1 C:> %systemroot%\system32\inetsrv\appcmd set app "Default Web Site/OldApplicationName" -path:/NewApplicationName 2   3     APP object "Default Web Site/OldApplicationName" changed Renaming Virtual Directories In IIS7 Open a command prompt to see all of your virtual directories. 1 C:> %systemroot%\system32\inetsrv\appcmd list appcmd 2   3     VDIR "Default Web Site/OldApplicationName/Images" (physicalPath:\\server\images) 4     VDIR "Default Web Site/OldApplicationName/Data/Config" (physicalPath:\\server\config) We want to rename /Images to /Images2 and /Data/Config to /Data/Config2. Here are the example commands: 1 C:> %systemroot%\system32\inetsrv\appcmd set vdir "Default Web Site/OldApplicationName/Images" -path:/Images2 2   3     VDIR object "Default Web Site/OldApplicationName/Images" changed 4   5 C:> %systemroot%\system32\inetsrv\appcmd set vdir "Default Web Site/OldApplicationName/Data/Config" -path:/Data/Config2 6   7     VDIR object "Default Web Site/OldApplicationName/Data/Config" changed

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  • How can I get Virtual Server 2005 R2 running on Windows Server 2008 R2?

    - by Bret Fisher
    For various reasons (old VT-less hardware, and .vhd support) we need to still run Virtual Server 2005 R2. It's just for lab/demo work but we'd like to run the host on the newest Windows OS possible. It's documented and at least partially supported to run the old Virtual Server 2005 R2 SP1 on Windows Server 2008 (non-R2). I've done that before. I'm wondering if anyone has gotten the scenario in the title above to work. This post says it's possible but has anyone here actually done it before I go through that process: http://blogs.infosupport.com/blogs/ericd/archive/2009/08/31/running-virtual-server-2005-r2-sp1-on-windows-server-2008-r2.aspx

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  • Virtual Linux

    <b>Datamation:</b> "The definition of virtual Linux is as fluid as the Linux platform itself. For the desktop user, virtual Linux translates into being able to use Linux without changing their existing operating system. For those working with servers however, virtual Linux can mean something very different altogether."

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  • VBoxHeadless - Running Virtual Machines With VirtualBox 3.1.x On A Headless Fedora 12 Server

    <b>Howtoforge:</b> "This guide explains how you can run virtual machines with Sun VirtualBox 3.1.x on a headless Fedora 12 server. Normally you use the VirtualBox GUI to manage your virtual machines, but a server does not have a desktop environment. Fortunately, VirtualBox comes with a tool called VBoxHeadless that allows you to connect to the virtual machines over a remote desktop connection, so there's no need for the VirtualBox GUI."

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  • Apache: Virtual Host and .htacess for URL Rewriting not working

    - by parth
    I have configured a virtual host in my local machine and every thing is working fine. Now I want to use SEO friendly urls. To achieve this I have used the .htaccess file. My virtual host configuration is: <VirtualHost *:80> DocumentRoot "C:/xampp/htdocs/ypp" ServerName ypp.com ServerAlias www.ypp.com ##ErrorLog "logs/dummy-host2.localhost-error.log" ##CustomLog "logs/dummy-host2.localhost-access.log" combined </VirtualHost> and my .htaccess file has: AllowOverride All RewriteEngine On RewriteBase /ypp/ RewriteRule ^/browse$ /browse.php RewriteRule ^/browse/([a-z]+)$ /browse.php?cat=$1 RewriteRule ^/browse/([a-z]+)/([a-z]+)$ /browse.php?cat=$1&subcat=$2 The above .htaccess setting is not working. After that I modified my virtual host setting and it is working. The new virtual host setting is: <VirtualHost *:80> RewriteEngine On RewriteRule ^/browse$ /browse.php RewriteRule ^/browse/([a-z]+)$ /browse.php?cat=$1 RewriteRule ^/browse/([a-z]+)/([a-z]+)$ /browse.php?cat=$1&subcat=$2 ServerAdmin [email protected] DocumentRoot "C:/xampp/htdocs/ypp" ServerName ypp.com ServerAlias www.ypp.com ##ErrorLog "logs/dummy-host2.localhost-error.log" ##CustomLog "logs/dummy-host2.localhost-access.log" combined <Directory "C:/xampp/htdocs/ypp"> AllowOverride All </Directory> </VirtualHost> Please let me know where I am going wrong in the .htacess file for url rewriting. I do not want to use the settings in virtual host, since for every change I have restart apache.

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  • How To Enlarge a Virtual Machine’s Disk in VirtualBox or VMware

    - by Chris Hoffman
    When you create a virtual hard disk in VirtualBox or VMware, you specify a maximum disk size. If you want more space on your virtual machine’s hard disk later, you’ll have to enlarge the virtual hard disk and partition. Note that you may want to back up your virtual hard disk file before performing these operations – there’s always a chance something can go wrong, so it’s always good to have backups. However, the process worked fine for us. Image Credit: flickrsven How To Create a Customized Windows 7 Installation Disc With Integrated Updates How to Get Pro Features in Windows Home Versions with Third Party Tools HTG Explains: Is ReadyBoost Worth Using?

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  • Manage SQL Server Connectivity through Windows Azure Virtual Machines Remote PowerShell

    - by SQLOS Team
    Manage SQL Server Connectivity through Windows Azure Virtual Machines Remote PowerShell Blog This blog post comes from Khalid Mouss, Senior Program Manager in Microsoft SQL Server. Overview The goal of this blog is to demonstrate how we can automate through PowerShell connecting multiple SQL Server deployments in Windows Azure Virtual Machines. We would configure TCP port that we would open (and close) though Windows firewall from a remote PowerShell session to the Virtual Machine (VM). This will demonstrate how to take the advantage of the remote PowerShell support in Windows Azure Virtual Machines to automate the steps required to connect SQL Server in the same cloud service and in different cloud services.  Scenario 1: VMs connected through the same Cloud Service 2 Virtual machines configured in the same cloud service. Both VMs running different SQL Server instances on them. Both VMs configured with remote PowerShell turned on to be able to run PS and other commands directly into them remotely in order to re-configure them to allow incoming SQL connections from a remote VM or on premise machine(s). Note: RDP (Remote Desktop Protocol) is kept configured in both VMs by default to be able to remote connect to them and check the connections to SQL instances for demo purposes only; but not actually required. Step 1 – Provision VMs and Configure Ports   Provision VM1; named DemoVM1 as follows (see examples screenshots below if using the portal):   Provision VM2 (DemoVM2) with PowerShell Remoting enabled and connected to DemoVM1 above (see examples screenshots below if using the portal): After provisioning of the 2 VMs above, here is the default port configurations for example: Step2 – Verify / Confirm the TCP port used by the database Engine By the default, the port will be configured to be 1433 – this can be changed to a different port number if desired.   1. RDP to each of the VMs created below – this will also ensure the VMs complete SysPrep(ing) and complete configuration 2. Go to SQL Server Configuration Manager -> SQL Server Network Configuration -> Protocols for <SQL instance> -> TCP/IP - > IP Addresses   3. Confirm the port number used by SQL Server Engine; in this case 1433 4. Update from Windows Authentication to Mixed mode   5.       Restart SQL Server service for the change to take effect 6.       Repeat steps 3., 4., and 5. For the second VM: DemoVM2 Step 3 – Remote Powershell to DemoVM1 Enter-PSSession -ComputerName condemo.cloudapp.net -Port 61503 -Credential <username> -UseSSL -SessionOption (New-PSSessionOption -SkipCACheck -SkipCNCheck) Your will then be prompted to enter the password. Step 4 – Open 1433 port in the Windows firewall netsh advfirewall firewall add rule name="DemoVM1Port" dir=in localport=1433 protocol=TCP action=allow Output: netsh advfirewall firewall show rule name=DemoVM1Port Rule Name:                            DemoVM1Port ---------------------------------------------------------------------- Enabled:                              Yes Direction:                            In Profiles:                             Domain,Private,Public Grouping:                             LocalIP:                              Any RemoteIP:                             Any Protocol:                             TCP LocalPort:                            1433 RemotePort:                           Any Edge traversal:                       No Action:                               Allow Ok. Step 5 – Now connect from DemoVM2 to DB instance in DemoVM1 Step 6 – Close port 1433 in the Windows firewall netsh advfirewall firewall delete rule name=DemoVM1Port Output: Deleted 1 rule(s). Ok. netsh advfirewall firewall show  rule name=DemoVM1Port No rules match the specified criteria.   Step 7 – Try to connect from DemoVM2 to DB Instance in DemoVM1  Because port 1433 has been closed (in step 6) in the Windows Firewall in VM1 machine, we can longer connect from VM3 remotely to VM1. Scenario 2: VMs provisioned in different Cloud Services 2 Virtual machines configured in different cloud services. Both VMs running different SQL Server instances on them. Both VMs configured with remote PowerShell turned on to be able to run PS and other commands directly into them remotely in order to re-configure them to allow incoming SQL connections from a remote VM or on on-premise machine(s). Note: RDP (Remote Desktop Protocol) is kept configured in both VMs by default to be able to remote connect to them and check the connections to SQL instances for demo purposes only; but not actually needed. Step 1 – Provision new VM3 Provision VM3; named DemoVM3 as follows (see examples screenshots below if using the portal): After provisioning is complete, here is the default port configurations: Step 2 – Add public port to VM1 connect to from VM3’s DB instance Since VM3 and VM1 are not connected in the same cloud service, we will need to specify the full DNS address while connecting between the machines which includes the public port. We shall add a public port 57000 in this case that is linked to private port 1433 which will be used later to connect to the DB instance. Step 3 – Remote Powershell to DemoVM1 Enter-PSSession -ComputerName condemo.cloudapp.net -Port 61503 -Credential <UserName> -UseSSL -SessionOption (New-PSSessionOption -SkipCACheck -SkipCNCheck) You will then be prompted to enter the password.   Step 4 – Open 1433 port in the Windows firewall netsh advfirewall firewall add rule name="DemoVM1Port" dir=in localport=1433 protocol=TCP action=allow Output: Ok. netsh advfirewall firewall show rule name=DemoVM1Port Rule Name:                            DemoVM1Port ---------------------------------------------------------------------- Enabled:                              Yes Direction:                            In Profiles:                             Domain,Private,Public Grouping:                             LocalIP:                              Any RemoteIP:                             Any Protocol:                             TCP LocalPort:                            1433 RemotePort:                           Any Edge traversal:                       No Action:                               Allow Ok.   Step 5 – Now connect from DemoVM3 to DB instance in DemoVM1 RDP into VM3, launch SSM and Connect to VM1’s DB instance as follows. You must specify the full server name using the DNS address and public port number configured above. Step 6 – Close port 1433 in the Windows firewall netsh advfirewall firewall delete rule name=DemoVM1Port   Output: Deleted 1 rule(s). Ok. netsh advfirewall firewall show  rule name=DemoVM1Port No rules match the specified criteria.  Step 7 – Try to connect from DemoVM2 to DB Instance in DemoVM1  Because port 1433 has been closed (in step 6) in the Windows Firewall in VM1 machine, we can no longer connect from VM3 remotely to VM1. Conclusion Through the new support for remote PowerShell in Windows Azure Virtual Machines, one can script and automate many Virtual Machine and SQL management tasks. In this blog, we have demonstrated, how to start a remote PowerShell session, re-configure Virtual Machine firewall to allow (or disallow) SQL Server connections. References SQL Server in Windows Azure Virtual Machines   Originally posted at http://blogs.msdn.com/b/sqlosteam/

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  • Ubuntu 12.10 installation in virtual box

    - by Rohit Pandey
    I am trying to install Ubuntu 12.10 as guest in virtual box in Windows 7 machine. After intallation and copying the files it asks me to restart Now and I click that button but I get an error that Virtual box stopped working and it prompts me to close the virtual box. When i restart Virtual box, Status in the Ubuntu is displayed as Aborted and after restarting it tries to reinstall Ubuntu. I have tried thrice. Please guide me how to resolve this issue. Regards, Rohit.

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  • Announcement Oracle Virtual Networking

    - by uwes
    Oracle Virtual Networking information and collateral are now available on Oracle.com and Oracle Technical Network (OTN). Oracle Virtual Networking revolutionizes data center economics with a complete portfolio of hardware and software products to provision and manage virtual I/O and networks for servers and storage. These products are available for ordering now. They were part of the Xsigo acquisition on November 6, 2012. For More Information Go To: Oracle Fabric Interconnect oracle.com OTN Oracle Fabric Manager oracle.com OTN Oracle Fabric Monitor oracle.com OTN Oracle SDN oracle.com OTN

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  • Apache: Virtual Host and .htacess for URL Rewriting not working

    - by parth
    I have configured virtual host in my local machine and every thing working fine . Now I want to use SEO friendly urls. To achive this I have used .htacess file . My virtual host configuration is : <VirtualHost *:80> DocumentRoot "C:/xampp/htdocs/ypp" ServerName ypp.com ServerAlias www.ypp.com ##ErrorLog "logs/dummy-host2.localhost-error.log" ##CustomLog "logs/dummy-host2.localhost-access.log" combined </VirtualHost> and my .htacess file has : AllowOverride All RewriteEngine On RewriteBase /ypp/ RewriteRule ^/browse$ /browse.php RewriteRule ^/browse/([a-z]+)$ /browse.php?cat=$1 RewriteRule ^/browse/([a-z]+)/([a-z]+)$ /browse.php?cat=$1&subcat=$2 The above .htacess setting is not working . After that I have modigied my virtual host setting and it is working . new virtual host setting is : <VirtualHost *:80> RewriteEngine On RewriteRule ^/browse$ /browse.php RewriteRule ^/browse/([a-z]+)$ /browse.php?cat=$1 RewriteRule ^/browse/([a-z]+)/([a-z]+)$ /browse.php?cat=$1&subcat=$2 ServerAdmin [email protected] DocumentRoot "C:/xampp/htdocs/ypp" ServerName ypp.com ServerAlias www.ypp.com ##ErrorLog "logs/dummy-host2.localhost-error.log" ##CustomLog "logs/dummy-host2.localhost-access.log" combined <Directory "C:/xampp/htdocs/ypp"> AllowOverride All </Directory> </VirtualHost> Please guide me where I am wrong in .htacess file for url rewriting . I donot want to use setting in virtual host because for every change I have restart apache .

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  • virtual host not working in windows7 xampp

    - by K.B Panamaldeniya-littletipz
    hi i am using windows7 and xampp , i want to create a virtual host . so i added 127.0.0.1 myawesomeproject to my C:\Windows\System32\drivers\etc\hosts like this # Copyright (c) 1993-2009 Microsoft Corp. # # This is a sample HOSTS file used by Microsoft TCP/IP for Windows. # # This file contains the mappings of IP addresses to host names. Each # entry should be kept on an individual line. The IP address should # be placed in the first column followed by the corresponding host name. # The IP address and the host name should be separated by at least one # space. # # Additionally, comments (such as these) may be inserted on individual # lines or following the machine name denoted by a '#' symbol. # # For example: # # 102.54.94.97 rhino.acme.com # source server # 38.25.63.10 x.acme.com # x client host # localhost name resolution is handled within DNS itself. 127.0.0.1 localhost 127.0.0.1 myawesomeproject ::1 localhost and i added some lines to C:\xampp\apache\conf\extra\httpd-vhosts.conf like this # # Virtual Hosts # # If you want to maintain multiple domains/hostnames on your # machine you can setup VirtualHost containers for them. Most configurations # use only name-based virtual hosts so the server doesn't need to worry about # IP addresses. This is indicated by the asterisks in the directives below. # # Please see the documentation at # <URL:http://httpd.apache.org/docs/2.2/vhosts/> # for further details before you try to setup virtual hosts. # # You may use the command line option '-S' to verify your virtual host # configuration. # # Use name-based virtual hosting. # NameVirtualHost *:80 # # VirtualHost example: # Almost any Apache directive may go into a VirtualHost container. # The first VirtualHost section is used for all requests that do not # match a ServerName or ServerAlias in any <VirtualHost> block. # ##<VirtualHost *:80> ##ServerAdmin [email protected] ##DocumentRoot "C:/xampp/htdocs/dummy-host.localhost" ##ServerName dummy-host.localhost ##ServerAlias www.dummy-host.localhost ##ErrorLog "logs/dummy-host.localhost-error.log" ##CustomLog "logs/dummy-host.localhost-access.log" combined ##</VirtualHost> ##<VirtualHost *:80> ##ServerAdmin [email protected] ##DocumentRoot "C:/xampp/htdocs/dummy-host2.localhost" ##ServerName dummy-host2.localhost ##ServerAlias www.dummy-host2.localhost ##ErrorLog "logs/dummy-host2.localhost-error.log" ##CustomLog "logs/dummy-host2.localhost-access.log" combined ##</VirtualHost> <VirtualHost *> DocumentRoot "C:\xampp\htdocs" ServerName localhost </VirtualHost> <VirtualHost *> <VirtualHost *:80> ServerAdmin [email protected] DocumentRoot c:\myawesomeproject ServerName localhost <Directory "c:\myawesomeproject"> Order allow,deny Allow from all </Directory> </VirtualHost> i created a folder called myawesomeproject in my c drive . when i type http://myawesomeproject it is rederecting to http://myawesomeproject/xampp i added another folder 'test' inside myawesomeproject . so the path to 'test' is C:/myawesomeproject/test . the problem is when i type http://myawesomeproject/test it gives an error. it says Object not found! The requested URL was not found on this server. If you entered the URL manually please check your spelling and try again. If you think this is a server error, please contact the webmaster. Error 404 myawesomeproject 8/22/2011 4:30:29 PM Apache/2.2.17 (Win32) mod_ssl/2.2.17 OpenSSL/0.9.8o PHP/5.3.4 mod_perl/2.0.4 Perl/v5.10.1 why is this . how can i create a virtual host........................ :(

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  • unity, seeing all instances of same open application windows on all virtual desktop

    - by Nasser M. Abbasi
    I noticed this strange issue with unity. I am using 12.04. The desktop has 4 virtual desktops, which I can switch between using the 'workspace switcher' which is very nice. But I noticed the following: When I have 2 instances of the same app (say 2 different firefox windows, or 2 different terminal windows), in 2 different virtual desktops, then I click on the icon for that application located on the launcher panel (the left long strip with icons on it), then I see the application comes into focus. Then when I click again right away (on the same icon on the launcher), then now all instances of this application that are open come into ONE view (may be on was on desktop 1, and the other was on desktop 3 for example) and then I can now click on the one instance window that I want to select to use. This is all very nice actually. But this does NOT work for all applications! I just tried it, and it worked for firefox, and for gedit and for the gnome terminal. I have one firefox window open in virtual desktop 1, and another window open in virtual desktop 2. I clicked once on the firefox icon, then again, and both windows came into the main desktop and I was able to select which one to use. When I tried the same thing on dolphin file manager, which I also had 2 windows (instances) of it open in 2 different virtual desktops, this behavior did not happen. I clicked again, and nothing happened. Only one remained in focus. So I had to fo look for the second dolphin window the hard way. It looks like some apps are supported by this feature and some are not. How does one make it so that all applications are supported like this? This is a very handy feature. Is it a configuration item somewhere? thanks

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  • Google I/O 2012 - Managing Google Compute Engine Virtual Machines Through Google App Engine

    Google I/O 2012 - Managing Google Compute Engine Virtual Machines Through Google App Engine Alon Levi, Adam Eijdenberg Google Compute Engine provides highly efficient and scalable virtual machines for large scale data processing operations. Integration with Google App Engine provides an orchestration framework to manage large virtual machine clusters used for data processing. This session will talk demonstrate integration and discuss future use cases of the two technologies. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 0 0 ratings Time: 51:06 More in Science & Technology

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  • Batch file to Delete Old Virtual Directories.

    - by Michael Freidgeim
    On some servers we have many old Virtual Directories created for previous versions of our application. IIS user interface allows to delete only one in a time. Fortunately we can use IIS scripts as described in How to manage Web sites and Web virtual directories by using command-line scripts in IIS 6.0 I've created batch file DeleteOldVDirs.cmd rem http://support.microsoft.com/kb/816568 rem syntax: iisvdir /delete WebSite [/Virtual Path]Name [/s Computer [/u [Domain\]User /p Password]] REM list all directories and create batch of deletes iisvdir /query "Default Web Site" echo "Enter Ctrl-C  if you want to stop deleting" Pause iisvdir /delete "Default Web Site/VDirName1" iisvdir /delete "Default Web Site/VDirName2" ...   If the name of WebSite or Virtual directory contain spaces(e.g  "Default Web Site"), don't forget to use double quotes. Note that the batch doesn't delete physical directories from flie system.You need to delete them using Windows Explorer, but it does support multiple selection!

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  • How to give virtual machine access to the Internet, but block from LAN?

    - by Pekka
    I am setting up a virtual machine using Microsoft Virtual PC in Windows 7. The VM will run a Windows XP. I want to set up a public-facing server in it for web pages, subversion and other things, and instruct the router to port forward any requests to that Virtual Machine. I managed to do that - I assigned the VM to the network adapter, and it is now acting as just another DHCP client - but to increase security I would like to block the VM from the rest of the LAN, so it accepts only incoming connections from the Internet. For this to be effective in case of a compromise, it would have to happen on VM level as far as I can see. Can this be done?

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  • Basis of definitions

    - by Yttrill
    Let us suppose we have a set of functions which characterise something: in the OO world methods characterising a type. In mathematics these are propositions and we have two kinds: axioms and lemmas. Axioms are assumptions, lemmas are easily derived from them. In C++ axioms are pure virtual functions. Here's the problem: there's more than one way to axiomatise a system. Given a set of propositions or methods, a subset of the propositions which is necessary and sufficient to derive all the others is called a basis. So too, for methods or functions, we have a desired set which must be defined, and typically every one has one or more definitions in terms of the others, and we require the programmer to provide instance definitions which are sufficient to allow all the others to be defined, and, if there is an overspecification, then it is consistent. Let me give an example (in Felix, Haskell code would be similar): class Eq[t] { virtual fun ==(x:t,y:t):bool => eq(x,y); virtual fun eq(x:t, y:t)=> x == y; virtual fun != (x:t,y:t):bool => not (x == y); axiom reflex(x:t): x == x; axiom sym(x:t, y:t): (x == y) == (y == x); axiom trans(x:t, y:t, z:t): implies(x == y and y == z, x == z); } Here it is clear: the programmer must define either == or eq or both. If both are defined, the definitions must be equivalent. Failing to define one doesn't cause a compiler error, it causes an infinite loop at run time. Defining both inequivalently doesn't cause an error either, it is just inconsistent. Note the axioms specified constrain the semantics of any definition. Given a definition of == either directly or via a definition of eq, then != is defined automatically, although the programmer might replace the default with something more efficient, clearly such an overspecification has to be consistent. Please note, == could also be defined in terms of !=, but we didn't do that. A characterisation of a partial or total order is more complex. It is much more demanding since there is a combinatorial explosion of possible bases. There is an reason to desire overspecification: performance. There also another reason: choice and convenience. So here, there are several questions: one is how to check semantics are obeyed and I am not looking for an answer here (way too hard!). The other question is: How can we specify, and check, that an instance provides at least a basis? And a much harder question: how can we provide several default definitions which depend on the basis chosen?

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  • How do I boot a virtual machine image from my network?

    - by Haabda
    I have many machines which require the same configurations. My goal is to boot them all from the network and load a virtual machine. It would be wonderful to have one image for all of our customer service machines. That way, I could load the virtual image, perform updates, and know the next time they boot up they will have all the changes. Ideally, the machines would store the image locally and only download a new image if there has been a change. With all the information out there on "desktop virtualization", "PXE booting", and "virtual machines", I feel lost. I have been reading for hours and feel like I have only just scratched the surface. I would like to do this using open source or free software. Any suggestions?

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  • New Virtual Compute Appliance Videos

    - by Cinzia Mascanzoni
    Watch the latest Virtual Compute Appliance videos to aid your conversations with partners and customers! Virtual Compute Appliance Flash demo shows your customers and partners the business benefits. VCA Product demo. Tier1 Customer Testimonial Video of using Oracle's Virtual Compute Appliance to build a private cloud virtualization platform to host its customers’ Oracle Enterprise and Windows applications. Centroid Partner Testimonial Video.

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  • How to setup the c++ rule of three in a virtual base class

    - by Minion91
    I am trying to create a pure virtual base class (or simulated pure virtual) my goal: User can't create instances of BaseClass. Derived classes have to implement default constructor, copy constructor, copy assignment operator and destructor. My attempt: class Base { public: virtual ~Base() {}; /* some pure virtual functions */ private: Base() = default; Base(const Base& base) = default; Base& operator=(const Base& base) = default; } This gives some errors complaining that (for one) the copy constructor is private. But i don't want this mimicked constructor to be called. Can anyone give me the correct construction to do this if this is at all possible?

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  • Why does linux-image-virtual depend on a generic kernel now?

    - by ændrük
    The linux-image-virtual metapackage has historically provided a kernel that is specifically designed for use in virtual machines: Ubuntu 8.04: linux-image-2.6.24-32-virtual Ubuntu 10.04: linux-image-2.6.32-44-virtual Ubuntu 11.10: linux-image-3.0.0-26-virtual Ubuntu 12.04: linux-image-3.2.0-32-virtual Apparently, this has now changed: Ubuntu 12.10: linux-image-3.5.0-17-generic What's the explanation? Is this still the correct kernel to use in a virtual machine?

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  • Do virtual machines perform better on the host HDD or USB drive?

    - by Jeremy Ricketts
    The question I'm asking is kind of general, and I'll give more specifics about my specific setup. Here's the main question though: Do virtual machines generally perform better on the host HDD or is it better to operate them from an external disk? My specific setup: A Macbook Pro with a nearly full internal SATA drive that spins at 7200. On this system I'm running large programs like Photoshop and some other RAM-intense applications. I've dedicated 2 of my 8 gigs of RAM to my VMware Fusion virtual machine, which runs Windows 7 and Visual Studio, sits on the same drive. When that thing boots up, my system really starts crawling. I have an external USB (specifics of that drive are here) which I'm thinking about moving the VM to. Obviously a USB drive is slower than my internal HDD, but maybe having two operating systems using the same disk is WORSE than putting one of them on a separate (albiet slower) disk. This a bad idea?

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