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  • Installing SATA dvd burner on machine with no spare SATA ports/connectors

    - by Faheem Mitha
    Greetings. I have the following motherboard Tyan Thunder K8WE S2895A2NRF Motherboard - extended ATX - nForce Pro 2200/2050 - Socket 940 - UDMA133, Serial ATA-300 (RAID) - 2 x Gigabit Ethernet - FireWire - 6-1 channel audio This is part of a computer that was assembled in the winter of 2006/2007. The user manual says the following with regard to SATA Integrated SATAII Generation 1 Controllers (from NForce Professional 2200) Two integrated dual port SATA II controllers Four SATA connectors support up to four drives 3 Gb/s per direction per channel NvRAID v2.0 support Supports RAID 0, 1, 0+1 and JBOD. I just purchased a SATA DVD burner. Here is the page for the product http://www.amazon.ca/gp/product/B002QGDWLK/ The problem I am facing is that I already have 4 SATA drives installed. I don't want to remove any of them. However, I want the DVD burner above installed as well. The person I am consulting with here (Bombay, India) tells me that my four available SATA ports are filled, and that my only option is to install a SATA card into the one free PCI slot on the motherboard. However, he says that with this setup I will not be able to boot from the DVD drive. Are these statements correct, and what are my other options if any? Even it the statements in the last para are true, I suppose I could use one of the motherboard connectors/ports there are currently being used with the hard drives with the DVD drive, and use the "add-on" connector with one of the hard drives. Not all the 4 hard drives need to be bootable. BTW, despite having read through http://en.wikipedia.org/wiki/Serial_ATA#Cables.2C_connectors.2C_and_ports I am fuzzy on the differences between connectors, cables and ports. Thanks in advance.

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  • Smart Array P400 battery failure

    - by RobIII
    The P400 Smart Array controller in my HP DL380G5 is indicating: Battery Status: Failed, Replace Battery 1 in the System Management Homepage. Also the IML indicates: POST Error: 1794-Drive Array - Array Accelerator Battery Charge Low I do have several replacement batteries (actually, several controllers including batteries) lying around at work but never had to actually replace one. I am wondering if the battery replacement (swap) could be done hot or if I need to take down my server to do the battery replacement. I have replaced other spare parts like fans and drives before and all those can be replaced hot. I just don't know about the battery of the P400 Smart Array controller. Any help would be appreciated. EDIT1 For those interested: straight from the horse's mouth: With thanks to Frands Hansen pointing it out here. EDIT2 In the end I did just power down, to be on the safe side and because the manual says so, and replace the battery. Couldn't be easier. Unplugged the old one of the end of the cable (not the end connected to the controller) and reconnected a spare one. The replaced battery is now in the server for about an hour and currently (still) recharging. I'm assuming all will end wel.

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  • JNDI / Classpath problem in glassfish

    - by Michael Borgwardt
    I am in the process of converting a large J2EE app from EJB 2 to EJB 3 (all stateless session beans, using glassfish 2.1.1), and running out of ideas. The first EJB I converted (let's call it Foo) ran without major problems (it was the only one in its ejb-module and I could completely replace the deployment descriptor with annotations) and the app ran fine. But after converting the second one (let's call it Bar, one of several in a different ejb-module) there is a weird combination of problems: The app deploys without errors (nothing in the logs either) There is an error when looking up Bar via JNDI When looking at the JNDI tree in the glassfish admin console, Bar is not present at all. Then when I look at the logs, I see this (Foo is the correct name of the EJB's remote interface of the first converted, previously working EJB): Caused by: javax.naming.NamingException: ejb ref resolution error for remote business interface Foo [Root exception is java.lang.ClassNotFoundException: Foo] at com.sun.ejb.EJBUtils.lookupRemote30BusinessObject(EJBUtils.java:425) at com.sun.ejb.containers.RemoteBusinessObjectFactory.getObjectInstance(RemoteBusinessObjectFactory.java:74) at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304) at com.sun.enterprise.naming.SerialContext.lookup(SerialContext.java:414) at com.sun.enterprise.naming.SerialContext.list(SerialContext.java:603) at javax.naming.InitialContext.list(InitialContext.java:395) at com.sun.enterprise.admin.monitor.jndi.JndiMBeanHelper.getJndiEntriesByContextPath(JndiMBeanHelper.java:106) at com.sun.enterprise.admin.monitor.jndi.JndiMBeanImpl.getNames(JndiMBeanImpl.java:231) ... 68 more Caused by: java.lang.ClassNotFoundException: XXX at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1578) at com.sun.ejb.EJBUtils.getBusinessIntfClassLoader(EJBUtils.java:679) at com.sun.ejb.EJBUtils.lookupRemote30BusinessObject(EJBUtils.java:348) ... 75 more This is followed by more exceptions for all the entries that (like Foo) do appear in the JNDI tree. These look like this: Caused by: javax.naming.NotContextException: BarHome cannot be listed at com.sun.enterprise.naming.SerialContext.list(SerialContext.java:607) at javax.naming.InitialContext.list(InitialContext.java:395) at com.sun.enterprise.admin.monitor.jndi.JndiMBeanHelper.getJndiEntriesByContextPath(JndiMBeanHelper.java:106) at com.sun.enterprise.admin.monitor.jndi.JndiMBeanImpl.getNames(JndiMBeanImpl.java:231) ... 68 more However, no exception for Bar, it does not appear in the log at all except one entry during deployment. The other EJBs in the same module do appear, as does Foo. Any ideas what could cause this or how to diagnose it further? The beans are pretty straightforward: @Stateless(name = "Foo") @RolesAllowed("FOOUSER") @TransactionAttribute(TransactionAttributeType.SUPPORTS) public class FooImpl extends BaseBean implements Foo { I'm also having some problems with the deployment descriptor for Bar (I'd like to eliminate it, but glassfish doesn't seem to like having a bean appear only in sun-ejb-jar.xml, or having some beans in a module declared in the descriptor and others use only annotations), but I can't see how that could cause the ClassNotFoundException on Foo. Is there a way to see the ClassPath that Glassfish is actually using?

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  • How do I merge cells of the same column in LyX?

    - by brickner
    I have 3 subfigures I want to arrange so that 1 will be in the left and 2 will be in the right (one above the other): Figure 1 | Figure 2 Figure 1 | Figure 3 Figure 1 should appear only once of course - across the entire column. I thought I should use 2x2 table to arrange them, but I can't find a way to merge the two cells in the same column to one cell in order to put figure 1 there. How can I merge the two cells in the same column?

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  • Forward differing hostnames to different internal IPs through NAT router

    - by abrereton
    Hi, I have one public IP address, one router and multiple servers behind the router. I would like to forward differing domains (All using HTTP) through the router to different servers. For example: example1.com => 192.168.0.110 example2.com => 192.168.0.120 foo.example2.com => 192.168.0.130 bar.example2.com => 192.168.0.140 I understand that this could be accomplished using Port Forwarding, but I need all hosts running on port 80. I found some information about IP Masquerading, but I found this difficult to understand, and I am not sure if it is what I am after. Another solution I have found is to direct all traffic to Reverse Proxy server, which forwards the requests onto the appropriate server. What about iptables? I am using a Billion 7404 VNPX router. Is there a feature that this router has that can accomplish this? Are these my only options? Have I missed something completely? Is one recommended over the others? I have searched around but I don't think I am hitting the correct keywords. Thanks in advance.

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  • Print jobs sent to server OK, but then get deleted

    - by Paul Morrison
    I have 2 HP computers, one running Win XP SP3, one running Win7. I have a Lexmark X4270 All-in-One printer attached to the Win7 machine via a USB port. I can print OK from the Win 7 machine, but when I print from the WinXP machine, the print job shows up in both print queues (showing the same number of bytes - which is good!), but then the status gets changed to "Deleting - Sent to printer", and that status shows up in both print queues. The print job then stays there until I do a cancel, followed by a system restart. FWIW the owner is shown as Guest, but I have permission for Everyone set to print... I believe I have up-to-date drivers; I don't believe it's a firewall problem. What I would like to see is the Win7 machine's reason for deleting my print jobs - is there a diagnostic tool available? Also, I notice that the port for this printer on the WinXP machine is set to USB001 - I would have thought something like \servername\sharedprinter would be more appropriate - and I can see that in the list of ports, but the system doesn't let me change the port name from USB001... Could someone shed some light? I have spent hours on this! TIA BTW I can do file sharing, no problem!

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  • client flips between internal and external IP addresses??

    - by jmiller-miramontes
    I have what seems like a not-particularly-complicated home network, all things considered: a DSL line comes in to a modem/router, which goes off to a switch, which supports a bunch of machines. My machines live in a 192.168.0.x address space; however, I'm running some public servers on the network, so I have a block of 8 (5, really) static IP addresses that are mapped to the servers by the router. The non-servers get 192.168.0.x addresses via NAT; some machines have static addresses and some get addresses from DHCP. Locally, I'm running a DNS server (named) to map between the domain names and the 192.168 address space. Somewhat messy, but everything basically works. Except: One of my local non-server clients occasionally switches from its internal address to its external address. That is, if I check the logs of a website I'm running internally, the hits coming from this client sometimes show up with the internal 192.168 address, and sometimes with the external (216.103...) address. It will flip back and forth for no apparent reason, without my doing anything. This can be a problem in terms of how the clients interact with the way I have some of the clients' SSH systems configured (e.g., allowing access from the internal network but not the external network), but it also Just Seems Wrong. I will confess that I'm kinda skating on the very edge of my networking competence here, but I can't for the life of me figure out what's going on. If it helps, the client in question is running Mac OS X / 10.6; its address is statically assigned, is not one of the five externally-accessible addresses, and gets its DNS from (first) the internal DNS server and (second) my ISP's DNS servers. I can't swear that none of the other NAT clients are also showing this problem; the one I'm dealing with is my everyday machine, so this is where I run into it. Does anybody out there have any advice? This is driving me crazy...

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  • Troubleshooting wireless connection problem / site survey?

    - by johnnyb10
    I just started in the IT department of a small company (200 users) and it's clear that one of the main problems that is driving everyone crazy is the spotty nature of the wireless connectivity throughout the office, particularly in certain conference rooms. This is a huge problem because the connection often drops during important presentations to clients. I was hired to help ease the load on the existing IT admin, who has done a great job, but is overloaded with many other tasks to deal with. So I would like to try to help out with this wireless issue. I am looking for advice on the best way to solve this problem--a realistic troubleshooting methodology that does not require me to spend any money. So far, I've experimented with Ekahau Heat Mapper, which is free and helps create a site survey. But I'm not exactly sure what I'm looking for or if there are other programs/tools/methods I should try as well. Any advice would be greatly appreciated. [Some background: The wireless setup consists of an HP ProCurve Mobility MSM (710?) controller that controls 10 access points throughout the building. There are three virtual wireless networks configured on the controller: one seems to be a default that cannot be changed, one is for internal employees and authenticates via Active Directory, and the third is a guest network for visitors. When I use HeatMapper, these show up as three different SSIDs, with different MAC addresses, all on the same channel. At first I thought maybe this would cause interference, but this seems to be the way the controller works;apparently, it automatically configures the channels to avoid interference from the other APs on the network.]

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  • web.config overrides app.config...why?

    - by vikp
    Hi, I have to DLLs: one with a web.config, another one with app.config I moved the connection strings from web.config to app.config so that it can be used by other DLLs. Now, when I call ConfigurationManager.GetSection("SomeSection") , the application looks for a web.config, when it should be looking for the app.config. It doesn't make sense why it does it because web.config is in a separate DLL. Can anybody explain this please?

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  • Listing both null and not null in mysql query

    - by tomasz
    Let's say I have the table NAME | ID | REF foo1 | 1 | NULL foo2 | 2 | 1234 foo2 | 3 | 567 foo1 | 4 | NULL foo3 | 5 | 89 I'd like to count all instances of NULL and NOT NULL in one query so that I can say NAME | null | not null foo1 | 0 | 2 foo2 | 2 | 0 foo3 | 0 | 1 I could run these two queries select NAME,count(*) from TABLE where REF is not null select NAME,count(*) from TABLE where REF is null But I'm sure there must be a simple way to do it in one mysql query.

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  • Optional non-system type parameters

    - by Courtney de Lautour
    C#4.0 obviously brings optional parameters (which I've been waiting for, for quite some time). However it seems that because only system types can be const that I cannot use any class/struct which I have created, as an optional param. Is there a some way which allows me to use a more complex type as an optional parameter. Or is this one of the realities that one must just live with?

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  • Virtual bridged networking with VLAN, could not ping

    - by v.yegy
    I require a virtual network with VLAN be build between two virtual hosts - which can be (lxc/ vbox -ubuntu or win xp). I tried with lxc and vbox with Ubuntu and was finding difficult to make it work without vlan, but was successful with vbox with xp. vbox-xp1 --- br1 ---------------- br2 ---- vbox-xp2 The config is: brctl addbr br1; brctl addbr br2 ifconfig br1 up; ifconfig br2 up stp br1 off; stp br2 off ip link add name br1-br2-l0 type veth peer name br1-br2-l1 sudo brctl addif br1 br1-br2-l0 sudo brctl addif br2 br1-br2-l1 vbox - xp 1 and 2 with network ; bridged and br1 and br2 respectively. The adapter is intel PRO/1000 MT Server and driver installed in guests. Configured IPs and two hosts pinged! VLAN config: ip link add link br1 name br1-2.5 type vlan id 5 brctl addif br2 br1-2.5 create vlan 5 in xp 1 and 2 and assign ip address Ping on with this config does not work. Wireshark trace on interface br1-br2-l1 / br1-2.5 shows that one ping results in ~240 ping packets and each growing by 4 bytes - first one being correct and 60, ping does not reach other host as I see mac is not learnt[arp -a]. -- if br1-2.5 is not configured, I see untagged packets in br1-br2-l1/0, but still not reaching other host as mac is not learnt. if br1-br2-l0/1 is made down, even if br1-2.5 is up, I count not see any packets. I tried with ebtables, but still could not make a correct config to work. -- If any one here are aware of any configuration, please let me know. I need to make a network of switches. Seems I have a very long way. Sorry for a very long question. Thanks and regards, vy

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  • Filtering a dropdown in Angular IE11 issue

    - by Brian S.
    I have a requirement for a select html element that can be duplicated multiple times on a page. The options for these select elements all come from a master list. All of the select elements can only show all of the items in the master list that have not been selected in any of the other select elements unless they just were duplicated. So I wrote a custom filter to do this in Angular and it seems to work just fine provided you are not using IE11. In IE when you select a new item from a duplicated select element, it seems to select the option after the one you selected even though the model still has the correct one set. I realize this sounds convoluted, so I created a jFiddle example. Using IE 11 try these steps: Select Bender Click the duplicate link Select Fry Notice that the one that is selected is Leela but the model still has Fry (id:2) as the one selected Now if you do the same thing in Chrome everything works as expected. Can anyone tell me how I might get around this or what I might be doing wrong? Here is the relevant Angular code: myapp.controller('Ctrl', function ($scope) { $scope.selectedIds = [{}]; $scope.allIds = [{ name: 'Bender', value: 1}, {name: 'Fry', value: 2}, {name: 'Leela', value: 3 }]; $scope.dupDropDown = function(currentDD) { var newDD = angular.copy(currentDD); $scope.selectedIds.push(newDD); } }); angular.module('appFilters',[]).filter('ddlFilter', function () { return function (allIds, currentItem, selectedIds) { //console.log(currentItem); var listToReturn = allIds.filter(function (anIdFromMasterList) { if (currentItem.id == anIdFromMasterList.value) return true; var areThereAny = selectedIds.some(function (aSelectedId) { return aSelectedId.id == anIdFromMasterList.value; }); return !areThereAny; }); return listToReturn; } }); And here is the relevant HTML <div ng-repeat="aSelection in selectedIds "> <a href="#" ng-click="dupDropDown(aSelection)">Duplicate</a> <select ng-model="aSelection.id" ng-options="a.value as a.name for a in allIds | ddlFilter:aSelection:selectedIds"> <option value="">--Select--</option> </select> </div>

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  • Time not propagating to machines on Windows domain

    - by rbeier
    We have a two-domain Active Directory forest: ourcompany.com at the root, and prod.ourcompany.com for production servers. Time is propagating properly through the root domain, but servers in the child domain are unable to sync via NTP. So the time on these servers is starting to drift, since they're relying only on the hardware clock. WHen I type "net time" on one of the production servers, I get the following error: Could not locate a time-server. More help is available by typing NET HELPMSG 3912. When I type "w32tm /resync", i get the following: Sending resync command to local computer The computer did not resync because no time data was available. "w32tm /query /source" shows the following: Free-running System Clock We have three domain controllers in the prod.ourcompany.com subdomain (overkill, but the result of a migration - we haven't gotten rid of one of the old ones yet.) To complicate matters, the domain controllers are all virtualized, running on two different physical hosts. But the time on the domain controllers themselves is accurate - the servers that aren't DCs are the ones having problems. Two of the DCs are running Server 2003, including the PDC emulator. The third DC is running Server 2008. (I could move the PDC emulator role to the 2008 machine if that would help.) The non-DC servers are all running Server 2008. All other Active Directory functionality works fine in the production domain - we're only seeing problems with NTP. I can manually sync each machine to the time source (the PDC emulator) by doing the following: net time \\dc1.prod.ourcompany.com /set /y But this is just a one-off, and it doesn't cause automated time syncing to start working. I guess I could create a scheduled task which runs the above command periodically, but I'm hoping there's a better way. Does anyone have any ideas as to why this isn't working, and what we can do to fix it? Thanks for your help, Richard

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  • Django : debugging templatetags

    - by interstar
    How on earth do people debug Django templatetags? I created one, based on a working example, my new tag looks the same to me as the existing one. But I just get a 'my_lib' is not a valid tag library: Could not load template library from django.templatetags.my_lib, No module named my_lib I know that this is probably because of something failing when defining the lib. But how do I see what's going on? What do you use to debug this situation?

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  • jQuery image gallery

    - by Dom
    Hello All, I am not sure if this will be right place to ask the question, but I have spent las 2 hours on Google trying to find something. Im looking for image gallery/sideshow that will look like the one on dell web site. Can anyone direct me to one please? I would really appreciate. Thanks Dom

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  • htaccess not properly rewriting urls

    - by Cameron Ball
    This is a bit of a weird one. I'm doing some work on a server, and I need rewrite rules for directories that actually exist (in some cases, they are more than one level deep) At the moment my .htaccess looks like this: RewriteEngine on RewriteRule ^simfiles/([-\ a-zA-Z0-9:/]+)$ http://mydomain.com/?portal=simfiles&folder=$1 [L] And this is working OK, for example, a url like: mydomain.com/sifmiles/my-files Will get redirected to mydomain.com/?portal=simfiles&folder=my-files Or in the case of a directory structure that is deeper than one level: mydomain.com/sifmiles/my-files/more-of-my-files Will get redirected to mydomain.com/?portal=simfiles&folder=my-files/more-of-my-files I wrote the regex so that it won't match things with a . in the path, because there are css and js files which reside in simfiles/somedirectory, and if I redirect everything then these cannot be loaded. I tried a configuration like this: RewriteEngine on RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^simfiles/([-\ a-zA-Z0-9:/\.]+)$ http://mydomain.com/?portal=simfiles&folder=$1 [L] But that doesn't work, things still don't load properly. So my first question is, how can I achieve this "properly"? I don't like my solution because it means redirects won't occur if the folder has a . in its name. My second problem, is that while the redirection is happening properly, the url becomes: http://mydomain.com/?portal=simfiles&folder=my-files I want the URL to remain clean, like: http://mydomain.com/sifmiles/my-files How can I achieve this?

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  • Need help tuning Mysql and linux server

    - by Newtonx
    We have multi-user application (like MailChimp,Constant Contact) . Each of our customers has it's own contact's list (from 5 to 100.000 contacts). Everything is stored in one BIG database (currently 25G). Since we released our product we have the following data history. 5 years of data history : - users/customers (200+) - contacts (40 million records) - campaigns - campaign_deliveries (73.843.764 records) - campaign_queue ( 8 millions currently ) As we get more users and table records increase our system/web app is getting slower and slower . Some queries takes too long to execute . SCHEMA Table contacts --------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------------+------------------+------+-----+---------+----------------+ | contact_id | int(10) unsigned | NO | PRI | NULL | auto_increment | | client_id | int(10) unsigned | YES | | NULL | | | name | varchar(60) | YES | | NULL | | | mail | varchar(60) | YES | MUL | NULL | | | verified | int(1) | YES | | 0 | | | owner | int(10) unsigned | NO | MUL | 0 | | | date_created | date | YES | MUL | NULL | | | geolocation | varchar(100) | YES | | NULL | | | ip | varchar(20) | YES | MUL | NULL | | +---------------------+------------------+------+-----+---------+----------------+ Table campaign_deliveries +---------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | newsletter_id | int(10) unsigned | NO | MUL | 0 | | | contact_id | int(10) unsigned | NO | MUL | 0 | | | sent_date | date | YES | MUL | NULL | | | sent_time | time | YES | MUL | NULL | | | smtp_server | varchar(20) | YES | | NULL | | | owner | int(5) | YES | MUL | NULL | | | ip | varchar(20) | YES | MUL | NULL | | +---------------+------------------+------+-----+---------+----------------+ Table campaign_queue +---------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+------------------+------+-----+---------+----------------+ | queue_id | int(10) unsigned | NO | PRI | NULL | auto_increment | | newsletter_id | int(10) unsigned | NO | MUL | 0 | | | owner | int(10) unsigned | NO | MUL | 0 | | | date_to_send | date | YES | | NULL | | | contact_id | int(11) | NO | MUL | NULL | | | date_created | date | YES | | NULL | | +---------------+------------------+------+-----+---------+----------------+ Slow queries LOG -------------------------------------------- Query_time: 350 Lock_time: 1 Rows_sent: 1 Rows_examined: 971004 SELECT COUNT(*) as total FROM contacts WHERE (contacts.owner = 70 AND contacts.verified = 1); Query_time: 235 Lock_time: 1 Rows_sent: 1 Rows_examined: 4455209 SELECT COUNT(*) as total FROM contacts WHERE (contacts.owner = 2); How can we optimize it ? Queries should take no more than 30 secs to execute? Can we optimize it and keep all data in one BIG database or should we change app's structure and set one single database to each user ? Thanks

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  • Kunagi LDAP configuration problems

    - by Willem de Vries
    We recently started with Scrum at our company and we wanted to start using Kunagi to test and see how it works. So I installed the kunagi_0.23.2.deb packet that I downloaded from their website, on my Ubuntu 11.04 running in tomcat6 using openjdk-6-jre. everything works fine except I can't get the LDAP to work. I have one AD server and one LDAP at my disposal for testing. For the LDAP I use the following info: -uri: ldap://192.168.1.11:389 -user: some_tested_user -passwd: the_pass -DN: dc=colosa,dc=net -LDAP Filter: (&(objectClass=user)) I tested various LDAP Filters, I don't know if I have the right one. However I get an erro when clicking "test LDAP". The error refers to the DN: Server service call error Calling service TestLdap failed. java.lang.RuntimeException: InvalidNameException: [LDAP: error code 34 - invalid DN] With the AD server I get no error while testing, yet I am not able to login I get: "Login faild" every time. I don't know if this is because of the LDAP Filter I entered, yet I can't get it to work. I have read this http://kunagi.org/iss652.html stating that I need to create my accounts inside Kunagi before I can login. So I did this with no effect. So basically my question is, what causes this DN string error (I am sure mine is right), and what LDAP Filter should i use? Any help would be highly appreciated.

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  • Implementing database redundancy with sharded tables

    - by ensnare
    We're looking to implement load balancing by horizontally sharding our tables across a cluster of servers. What are some options to implement live redundancy should a server fail? Would it be effective to do (2) INSERTS instead of one ... one to the target shard, and another to a secondary shard which could be accessed should the primary shard not respond? Or is there a better way? Thanks.

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  • Learning C bit manipulation

    - by VaioIsBorn
    I didn't know any better name for a title of the question. For ex: on one of my previous questions one answered ((a)-(b))&0x80000000) 31 - this is kind of a too advanced for me and i can't really get what it means. I am not looking just for an answer of that, but i need someone to tell me some books/sites/whatever where i can learn this cool "advanced" tricks in C - and learn how and where to use them respectively too.

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  • Diophantine Equation [closed]

    - by ANIL
    In mathematics, a Diophantine equation (named for Diophantus of Alexandria, a third century Greek mathematician) is a polynomial equation where the variables can only take on integer values. Although you may not realize it, you have seen Diophantine equations before: one of the most famous Diophantine equations is: X^n+Y^n=Z^n We are not certain that McDonald's knows about Diophantine equations (actually we doubt that they do), but they use them! McDonald's sells Chicken McNuggets in packages of 6, 9 or 20 McNuggets. Thus, it is possible, for example, to buy exactly 15 McNuggets (with one package of 6 and a second package of 9), but it is not possible to buy exactly 16 nuggets, since no non- negative integer combination of 6's, 9's and 20's adds up to 16. To determine if it is possible to buy exactly n McNuggets, one has to solve a Diophantine equation: find non-negative integer values of a, b, and c, such that 6a + 9b + 20c = n. Problem 1 Show that it is possible to buy exactly 50, 51, 52, 53, 54, and 55 McNuggets, by finding solutions to the Diophantine equation. You can solve this in your head, using paper and pencil, or writing a program. However you chose to solve this problem, list the combinations of 6, 9 and 20 packs of McNuggets you need to buy in order to get each of the exact amounts. Given that it is possible to buy sets of 50, 51, 52, 53, 54 or 55 McNuggets by combinations of 6, 9 and 20 packs, show that it is possible to buy 56, 57,..., 65 McNuggets. In other words, show how, given solutions for 50-55, one can derive solutions for 56-65. Problem 2 Write an iterative program that finds the largest number of McNuggets that cannot be bought in exact quantity. Your program should print the answer in the following format (where the correct number is provided in place of n): "Largest number of McNuggets that cannot be bought in exact quantity: n" Hints: Hypothesize possible instances of numbers of McNuggets that cannot be purchased exactly, starting with 1 For each possible instance, called n, a. Test if there exists non-negative integers a, b, and c, such that 6a+9b+20c = n. (This can be done by looking at all feasible combinations of a, b, and c) b. If not, n cannot be bought in exact quantity, save n When you have found six consecutive values of n that in fact pass the test of having an exact solution, the last answer that was saved (not the last value of n that had a solution) is the correct answer, since you know by the theorem that any amount larger can also be bought in exact quantity

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