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• UDP blocked by Windows XP Firewall when sending to local machine

  - by user36367

  Hi there, I work for a software development company but the issue doesn't seem to be programming-related. Here is my setup: - Windows XP Professional with Service Pack 3, all updated - Program that sends UDP datagrams - Program that receives UDP datagrams - Windows Firewall set to allow inbound UDP datagrams on a specific port (Scope: Subnet) If I send a UDP datagram on any port to other, similar machines, it goes through. If I send the UDP datagram to the same computer running the program that sends (whether using broadcast, localhost IP or the specific IP of the machine), the receiver program gets nothing. I've traced the problem down to the Windows XP Firewall, as Windows 7 does not have this problem (and I do not wish to sully my hands with Vista). If the exception I create for that UDP port in the WinXP firewall is set for a Scope of Subnet the datagram is blocked, but if I set it to All Computers or specifically enter my network settings (192.168.2.161 or 192.168.2.0/255.255.255.0) it works fine. Using different UDP ports makes no difference. I've tried different programs to reproduce this problem (ServerTalk to send and either IP Port Spy or PortPeeker to receive) to make sure it's not our code that's the issue, and those programs' datagrams were blocked as well. Also, that computer only has one network interface, so there are no additional network weirdness. I receive my IP from a DHCP server, so this is a straightforward setup. Given that it doesn't happen in Windows 7 I must assume it's a defect in the Windows XP Firewall, but I'd think someone else would have encountered this problem before. Has anyone encountered anything like this? Any ideas? Thanks in advance!

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• Internal Code Signing: Key Distribution, or Certificate Server?

  - by Myrddin Emrys

  I should first note that we have nobody in IT with significant familiarity with self-signed certification. We have a moderately sprawling network (one forest, many locations), and we are now rolling out internal code signing; until now users have run untrusted code, or we even disabled(!) the warnings. Intranet applications, scripts, and sites will now be signed with self certification. I am aware of two obvious ways we can deploy this: Distributing the keys directly via a group policy, and setting up a cert server. Can someone explain the trade-offs between these two methods? How many certs before the group policy method is unwieldy? Are they large enough that remote users will have issues? Does the group policy method distribute duplicates on every login? Is there a better method I am not aware of? I can find a lot of documentation on certifications and various ways to create them, but I have not been able to find something that summarizes the difference between the distribution methods and what criteria make one or the other superior.

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• Why do I need a managed switch and which one should I buy?

  - by ascanio1

  I bought a 2nd router and I want both routers to have direct WAN access to the modem. One of the 2 routers directs VOIP traffic to a telephone line port. This VOIP service is provided by the cable carrier which also leases the modem & the router. The cable company technician told me that this VOIP line uses IPv6 addressing and therefore I must employ an IPv6 capable/compliant Giga Hub/Switch or my telephone line won't work anymore. Pls advise me (brand/model) an IPv6 compliant, 2 port, switch to purchase. Pls educate me: By reading this forum I thought that hubs broadcast traffic to all ports, regardless of which input/output is being used and so, theoretically, they have nothing to do with IP. Correct? Same story for unmanaged switches, where the only difference is that these latter devices route traffic only to those ports which are detected to be in use. Correct? I also understood that unmanaged switches route traffic simply by detecting hardware use and not by selecting specific IP traffic. Correct? Finally, there are managed switches which DO select traffic based on IP and, therefore, only these managed switches are involved with IPv6... Why would my cable company explicitly tell me, over and over, that I must use an IPv6 compliant switch? Why would they need a managed switch instead of an unmanaged one? Thanks in advance for helping me understand!

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• Terminal emulation has stopped working. Garbage escape chars

  - by oligofren

  To enable me to do some remote administration of our servers I started using a terminal emulation program called TouchTerm Pro on my iPhone. While not the smoothest experience, it has allowed me to leave my computer behind when going out of town, which makes the slightly painful experience worthwhile. As of late, the app unfortunately no longer works. Pressing up and down keys after logging on via ssh gives me garbage like ^[[A and ^[[B. Combinations with Ctrl - like you can see in the video - no longer works either. Writing full command lines and executing by the enter key works though. Being able to search my bash history was the difference between a usable app and endless frustration, so getting it to work is essential. The app has (of course) met its end of life, not getting updated anymore. I am not quite sure, which side (client or server) that has to be "fixed"/hacked to make the control sequences work again. But is there something I can do to make it work as intended? You can see a video of TouchTerm in operation here.

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• How far should we take the N+N redundancy craziness ?

  - by Brann

  The industry standard when it comes from redundancy is quite high, to say the least. To illustrate my point, here is my current setup (I'm running a financial service). Each server has a RAID array in case something goes wrong on one hard drive .... and in case something goes wrong on the server, it's mirrored by another spare identical server ... and both server cannot go down at the same time, because I've got redundant power, and redundant network connectivity, etc ... and my hosting center itself has dual electricity connections to two different energy providers, and redundant network connectivity, and redundant toilets in case the two security guards (sorry, four) needs to use it at the same time ... and in case something goes wrong anyway (a nuclear nuke? can't think of anything else), I've got another identical hosting facility in another country with the exact same setup. Cost of reputational damage if down = very high Probability of a hardware failure with my setup : <<1% Probability of a hardware failure with a less paranoiac setup : <<1% ASWELL Probability of a software failure in our application code : 1% (if your software is never down because of bugs, then I suggest you doublecheck your reporting/monitoring system is not down. Even SQLServer - which is arguably developed and tested by clever people with a strong methodology - is sometimes down) In other words, I feel like I could host a cheap laptop in my mother's flat, and the human/software problems would still be my higher risk. Of course, there are other things to take into consideration such as : scalability data security the clients expectations that you meet the industry standard But still, hosting two servers in two different data centers (without extra spare servers, nor doubled network equipment apart from the one provided by my hosting facility) would provide me with the scalability and the physical security I need. I feel like we're reaching a point where redundancy is just a communcation tool. Honestly, what's the difference between a 99.999% uptime and a 99.9999% uptime when you know you'll be down 1% of the time because of software bugs ? How far do you push your redundancy crazyness ?

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• How to connect 2 routers (Asmax and D-link)

  - by piobyz

  I just bought a new router, D-link DSL 2641B and want to connect it to another one, provided by my ISP, Asmax AR 804MP. Previously, I had Linksys WRT350N, and there was no problem, while I had Ethernet cable plugged in to one of LAN ports in Asmax and INTERNET(RJ45) port in Linksys, connection used PPPoE protocol -- worked OK. D-link has DSL(RJ11) port (which I don't want to use as Asmax replacement, while there is a separate Ethernet cable with a TV plugged to Asmax, which I don't want to configure from scratch on D-link). How should I connect my new D-link to work with Asmax? Via DSL port? Via one of the LAN ports (in which case I probably should change the purpose of this port in the config, I guess?). I tried connecting D-link both ways: LAN(ASMAX) to LAN(DLINK) LAN(ASMAX) to DSL(DLINK) (using RJ11 - RJ45 cable) I hope there is some setting in the DLINK's config that I overlooked. I haven't tried to see what's in ASMAX's config, but I guess I don't need to change anything there, while Linksys worked just fine? The only difference I see, is that D-link has RJ11 DSL port as WAN, and Linksys has RJ45 (called by them INTERNET) as a main WAN port.

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• Trouble with Russian pc's on my wifi

  - by hogni89

  I have created a WiFi hotspot for the local community. The problem is, some Russian PC's (Windows XP, Windows Vista and Windows 7) can't get internet connection (We have a lot of bypassing russian fishing vessels / cargo ships). The pc's obtain a valid IP address, and some of them can even manage to send some few packages - But none of them are usable on the network. They all say "Limited internet access" or "???????????? ?????? ? ????????". The thing these PC's have in common is, that they all run a Russian installation of Windows. No one else has problems with the WiFi hotspot - Danish and English Windows, Linux and OS X all work like a charm. Can it be, that there is a difference between the danish / english windows installation, compared to the Russian installation? EDIT START They can't ping the router (One PC got one response - ONCE), they can't access any sites and Windows newer asks "Is this network public, home or work?". EDIT END PS: The hotspot is a airMAX rocket M from Ubiquiti Networks, Inc (www.ubnt.com)

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• windows 7 turns off itself everyday at about 9am

  - by Radek

  I was given this comp at work and after a week or so this strange thing started to happen in the middle of doing something :-( It turns off itself at about 9.10am every morning Just once a day and it works fine after it had it little nap. it happens both if the comp was on all night or I turned it off before leaving the office. I tried to swapped the memory as I was told that there was an issue with memory. But moving or removing any memory did not make any difference. I am not aware that I would install any program that could cause that. I installed AVG and set it up to do every day scan about 8am + if restart is needed it requires user confirmation. 'The Software Protection service has stopped' few minutes before it turned off itself but it happened also at other times without the computer turned off. I turned off Windows automatic updates as the first thing when I got the comp configuration Windows 7 Ultimate Intel Core2 Quad Q9550 at 2.8GH, 8GB RAM ST31000528AS Barracuda 7200.12 SATA 3Gb/s 1TB Update Below message are logged when I turn the comp on again. Message 1: The previous system shutdown at 9:08:54 AM on ?6/?29/?2010 was unexpected. Message 2: Level:Critical Source: Kernel Power EventID 41 Task Category (63) The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly. Log after manual restart Update 2 (task scheduler)

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• Distributed storage and computing

  - by Tim van Elteren

  Dear Serverfault community, After researching a number of distributed file systems for deployment in a production environment with the main purpose of performing both batch and real-time distributed computing I've identified the following list as potential candidates, mainly on maturity, license and support: Ceph Lustre GlusterFS HDFS FhGFS MooseFS XtreemFS The key properties that our system should exhibit: an open source, liberally licensed, yet production ready, e.g. a mature, reliable, community and commercially supported solution; ability to run on commodity hardware, preferably be designed for it; provide high availability of the data with the most focus on reads; high scalability, so operation over multiple data centres, possibly on a global scale; removal of single points of failure with the use of replication and distribution of (meta-)data, e.g. provide fault-tolerance. The sensitivity points that were identified, and resulted in the following questions, are: transparency to the processing layer / application with respect to data locality, e.g. know where data is physically located on a server level, mainly for resource allocation and fast processing, high performance, how can this be accomplished? Do you from experience know what solutions provide this transparency and to what extent? posix compliance, or conformance, is mentioned on the wiki pages of most of the above listed solutions. The question here mainly is, how relevant is support for the posix standard? Hadoop for example isn't posix compliant by design, what are the pro's and con's? what about the difference between synchronous and asynchronous opeartion of a distributed file system. Though a synchronous distributed file system has the preference because of reliability it also imposes certain limitations with respect to scalability. What would be, from your expertise, the way to go on this? I'm looking forward to your replies. Thanks in advance! :) With kind regards, Tim van Elteren

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• Issues Deploying Functional WAR to Elastic Beanstalk with Tomcat7

  - by BFar

  I am currently deploying OpenTripPlanner (http://github.com/OpenPlans/OpenTripPlanner.git) to Elastic Beanstalk. I'm able to successfully build and deploy opentripplanner with my own customized settings on an ec2. I have set it up so that the appropriate WAR file can be placed in the Tomcat/Webapps folder, and when Tomcat is started up, it will auto-deploy, and even download open trip planner's graph.obj from an S3. All of that works just fine, except when I try to deploy to Elastic Beanstalk. When I upload to Elastic Beanstalk, the log shows that my WAR file is successfully unpacked & successfully downloads the graph.obj from my S3. The only difference is that then nothing happens and I can't load the site in my browser. The health is RED, and I can't figure out what is going on. I've tried looking into ports and dns issues, but I can't determine what's wrong. Anyone have any ideas? Why would a WAR that works on tomcat7 outside of Beanstalk fail to be accessible?

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• Only tunnel certain applications via OpenVPN

  - by jinjin

  Hi, I've purchased a VPN solution, it works correctly when I have "redirect-gateway def1" in the configuration file (routing all traffic through the VPN). However when I remove that line from the configuration file, I am still able to ping-out of the machine (ping -I tap0), however I cannot ping the IP assigned to the machine (it's a public ip), i get the error: Destination Host Unreachable. I only want to have certain applications sending traffic through the VPN tunnel (eg: ZNC, irssi), all of which i can select which IP they use. However they can't recieve any data, making the tunnel essentially useless to me when disabling redirect-gateway. Any ideas on how to allow specific applications use the tunnel, without of forcing everything to go through it? My configuration file is as follows: dev tap remote #.#.#.# float #.#.#.# port 5129 comp-lzo ifconfig #.#.#.# 255.255.255.128 route-gateway #.#.#.# #redirect-gateway def1 secret key.txt cipher AES-128-CBC The output of ifconfig -a when the tunnel is connected: tap0 Link encap:Ethernet HWaddr 00:ff:47:d3:6d:f3 inet addr:#.#.#.# Bcast:#.#.#.# Mask:255.255.255.255 inet6 addr: <snip> Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:612 errors:0 dropped:0 overruns:0 frame:0 TX packets:35 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:25704 (25.1 KiB) TX bytes:6427 (6.2 KiB) EDIT: the Bcast:#.#.#.# (ifconfig) is different from route-gateway #.#.#.# (openvpn) if that makes any difference.

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• Formula-based Excel page headers

  - by Jake Krohn

  I'm using the "Rows to repeat at top" function in Excel's "Page Setup" dialog to ensure that a multi-row header block appears on every printed page of my worksheet. However, I'd like to be able to change certain bits of the header based on the content of the current page. I would simply like to display the value of one cell in the first row that is printed on the page. If this is my header: Section: xx And the data looks like this (columns are Section and Name): 1 Foo 1 Bar 2 Baz I want the "xx" in the header to be "1". If, further down on the next page, the value in the Section column is "3", I want that printed in the header of the next page. I originally thought that using the "OFFSET" function might help, e.g. ="Section: "&OFFSET(A2, 1, 0) But it only shows the offset from the original placement of the header, thus only working on page 1. The end document is a PDF, so right now I'm able to go back in with the "TouchUp Text Tool" in Acrobat and add the numbers page by page. But it gets to be a tedious process with 70+ page reports. Anyone have any better ideas that don't require me mucking up the original Excel document with inserted headers every N lines? This is Excel 2008 for Mac, if it makes a difference.

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• Anonymous Login attemps from IPs all over Asia, how do I stop them from being able to do this?

  - by Ryan

  We had a successful hack attempt from Russia and one of our servers was used as a staging ground for further attacks, actually somehow they managed to get access to a Windows account called 'services'. I took that server offline as it was our SMTP server and no longer need it (3rd party system in place now). Now some of our other servers are having these ANONYMOUS LOGIN attempts in the Event Viewer that have IP addresses coming from China, Romania, Italy (I guess there's some Europe in there too)... I don't know what these people want but they just keep hitting the server. How can I prevent this? I don't want our servers compromised again, last time our host took our entire hardware node off of the network because it was attacking other systems, causing our services to go down which is really bad. How can I prevent these strange IP addresses from trying to access my servers? They are Windows Server 2003 R2 Enterprise 'containers' (virtual machines) running on a Parallels Virtuozzo HW node, if that makes a difference. I can configure each machine individually as if it were it's own server of course... UPDATE: New login attempts still happening, now these ones are tracing back to Ukraine... WTF.. here is the Event: Successful Network Logon: User Name: Domain: Logon ID: (0x0,0xB4FEB30C) Logon Type: 3 Logon Process: NtLmSsp Authentication Package: NTLM Workstation Name: REANIMAT-328817 Logon GUID: - Caller User Name: - Caller Domain: - Caller Logon ID: - Caller Process ID: - Transited Services: - Source Network Address: 94.179.189.117 Source Port: 0 For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. Here is one from France I found too: Event Type: Success Audit Event Source: Security Event Category: Logon/Logoff Event ID: 540 Date: 1/20/2011 Time: 11:09:50 AM User: NT AUTHORITY\ANONYMOUS LOGON Computer: QA Description: Successful Network Logon: User Name: Domain: Logon ID: (0x0,0xB35D8539) Logon Type: 3 Logon Process: NtLmSsp Authentication Package: NTLM Workstation Name: COMPUTER Logon GUID: - Caller User Name: - Caller Domain: - Caller Logon ID: - Caller Process ID: - Transited Services: - Source Network Address: 82.238.39.154 Source Port: 0 For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

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• Subversion error: Repository moved permanently to please relocate

  - by Bart S.

  I've set up subversion and apache on my server. If I browse to it through my webbrowser it works fine (http://svn.host.com/reposname). However, if I do a checkout on my machine I get the following error: Command: Checkout from http://svn.host.com/reposname, revision HEAD, Fully recursive, Externals included Error: Repository moved permanently to 'http://svn.host.com/reposname/'; please relocate I checked apache's error log, but it doesn't say anything. (it does now - see edit) My repositories are stored under: /var/www/svn/repos/ My website is stored under: /var/www/vhosts/x/... Here's the conf file for the subdomain: <Location /> DAV svn SVNParentPath /var/www/svn/repos/ AuthType Basic AuthName "Authorization Realm" AuthUserFile /var/www/svn/auth/svn.htpasswd Require valid-user </Location> Authentication works fine. Does anyone know what might be causing this? -- Edit So I restarted apache (again) and tried it again and now it give me an error message, but it doesn't really help. Anyone have an idea what it means? [Wed Mar 31 23:41:55 2010] [error] [client my.ip.he.re] Could not fetch resource information. [403, #0] [Wed Mar 31 23:41:55 2010] [error] [client my.ip.he.re] (2)No such file or directory: The URI does not contain the name of a repository. [403, #190001] -- Edit 2 If I do svn info it doesn't give anything usefull: [root@eduro eduro.nl]# svn info http://svn.domain.com/repos/ Username: username Password for 'username': svn: Repository moved permanently to 'http://svn.domain.com/repos/'; please relocate I also tried doing a local checkout (svn checkout file:///var/www/svn/repos/reposname) and that works fine (also adding / commiting works fine). So it seems is has something to do with apache. Some other information: I'm running CentOs 5.3 Plesk 9.3 Subversion, version 1.6.9 (r901367) -- Edit 3 I tried moving the repositories, but it didn't make any difference. selinux is disabled so that isn't it either. -- Edit 4 Really? Nobody :(?

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• Load balancing with puppet

  - by Gonçalo Queirós

  Hi there. Im trying to setup a loadbalancing system. My load balancer (nginx) has a conf file where i should list all IP's of the upstream servers. I could put the IP's on the conf manually, but this ways i would need to change the conf file every time i add/remove an upstream server. For now i came up with two different ideas, but i don't like much of neither: 1 - Have every upstream machine to use Exported Resources to create a file with it's IP..Then the load balancer server will have an "include conf_directory/*", and load all the files created by the upstrem servers. Since the load balancer is using nginx this can be done, but if i wan't latter on to configure something that doesn't have the "include" on the conf files, this solution will not work. 2 - If the config doesn't support the "include" command, then we could have again, every upstream server use the Exported Resources to create a filw with its IP, and latter on, the load balancer execute a command that would pick every file and generate the config Both versions addopt the same techinque, the difference is that version 2 is used when the server (that needs to have a conf generated) doesn't recognize a command like "include" inside its own conf. Now, my question is, is there any way to do this in a different form? I suspect that there is, since puppet is made to manage multiple servers, it seems a bit strange not have a easy way to configure load balancers.

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• Puzzling TCP performance over 3G / UMTS

  - by lemonsqueeze

  I'm using 3G as my primary internet connection, and TCP over this thing is getting more puzzling every day. For example: Downloading from kernel.org is crazy fast: $wget http://www.kernel.org/pub/linux/kernel/v3.0/linux-3.6.8.tar.bz2 increases to ~500kB/s after a few secs ! Some servers are incredibly slow, for instance www.graphic-pc.com:Same thing, downloading a big file with wget it starts at ~30kB/s for a split second, then collapses to 5-10k or even worse. Web browsing is decent but somewhat unreliable. Randomly, a page will take really long to load or even fail to load, but a reload can succeed almost immediately. Now, by chance i started playing with OpenVPN over UDP on top of the 3G connection, and OMG suddenly everything's extremely fast !Same www.graphic-pc.com now shoots at 100-200kB/s ! What's going on here ??? How come it is so much better with the VPN than without ?? And why does graphic-pc.com crawl when kernel.org flies ?Something to do with my tcp stack (or the server), or some buggy router in between ?? Notes: Setup is laptop running Ubuntu Lucid and a Huawei 3G dongle (So direct pppd connection). I can reproduce this pretty much any time during the day and I'm not moving, so it's clearly not cell environment or internet congestion. (although kernel.org without VPN sometimes does worse in the evening, 60kB or so - but still 500kB with VPN !) For 2) wireshark shows retransmitted packets, dup ack's, even out of order sometimes. I've tried playing with different /proc/sys/net/ipv4 parameters (tcp_rmem, window_scaling, tcp_congestion...) doesn't seem to make a difference. Update: Tried under windows 7 (no VPN) with some interesting results: tcp settings : default tcp_optimizer kernel.org : 10 kB/s 20 kB/s graphic-pc.com: 8 kB/s 70 kB/s ! tcp_optimizer turned on ctcp among other things. Have to check what os graphic-pc.com is running, my bet is linux's tcp_westwood and ms ctcp don't mix well here...

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• WAMP Installation - Multiple PHP Version Issues

  - by Pete171

  I have installed WAMP because I am attempting to modify an an application which uses Zend Optimizer (I cannot use Z.O. with PHP5.3+, which is why I decided to install WAMP). I downloaded the latest version - Wamp Server 2.1 - which comes bundled with PHP5.3.5. I then downloaded a PHP version that would be compatible with Z.O. - 5.2.9. - and a compatible Apache version, 2.0.63. My problem: PHP scripts run fine, but anything with MySQL does not work. Running the testmysql.php script returns the fatal error: Fatal error: Call to undefined function mysql_connect() in C:\wamp\www\testmysql.php on line 2". I have looked in the PHP INI files inside both PHP versions, and I'm fairly sure the relevant information is there. At least, there are parts inside that mention MySQL! Perhaps somebody could clarify exactly what information should be present? Also, when visiting a page that called phpinfo(), I noticed that the 'Loaded Configuration File' was pointing to C:\wamp\bin\php\php5.3.5\php.ini, even though I have enabled the older PHP version. I've stopped and started Apache, too, and that hasn't made a difference. Is anybody able to offer any assistance? Anything at all would be great; I'm not very good at messing around with Apache/

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• IBM BladeCenter S: Disk Configuration

  - by gravyface

  Have just the one storage bay right now (SAS 15K 600GB x 6) and have configured one storage pool in RAID 10 with 4 disks (and two global spares). For each blade, I've created a volume and mapped accordingly: Blade #1 400 GB Blade #2 200 GB Blade #3 100 GB Blade #4 100 GB When I boot up Blade 1 and enter into the UEFI Setup (F1) followed by the Adapters and UEFI Drivers LSI Logic Fusion MPT SAS Driver Utility, I see 4 disks: two are the on-board 73GB drives, the other two are 200GB each and assume I'm being presented with two logical disks from the volume I created and mapped to this blade. I was a bit surprised by this: I figured I would've been presented with one logical drive per volume, not two. I'm assuming I can just configure whatever RAID level I wish that supports two disks, but not really sure what the benefits/trade-offs here. Should I go with RAID 10 on top of RAID 10? RAID 0? Software RAID 0/1/10? Does it even matter? If this is "normal" to see two disks, then I'm going to likely just do some benchmarking and see if it makes a difference changing the RAID levels (my guess is no); if this is not normal, well, please let me know. :)

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• Router vs switch in a LAN [closed]

  - by servernewbie

  If I have a LAN and and connect it with a switch, I understand it uses a CAM table to route packets in layer 2 (by saving mac to port relations). So far all good. However, when using a router for a LAN (ONLY for a LAN, not to connect it to "the outside" WAN/internet/etc) I get a bit confused as to how it internally processes packets. I would first split this into two router scenarios: Router with buit-in switch In this scenario, I would expect that it will act exactly as a switch with a CAM table internally. This would probably benefit a bit in speed (guessing here?) compared to the next option. Router without built-in switch Here is where I get confused. If hostA wants to send a packet to hostB, it will ARP to find hostB's MAC address and send it there. Now, if we had a switch (above scenario) this would be easy. But how does it work now in a router WITHOUT a switch? If I would guess, hostA would send an Ethernet frame with hostB's MAC address to the line. The router would fetch the packet (even though the router has another MAC address, it would still fetch this packet even if it only contains hostB's MAC address). It would strip the Ethernet frame header and check the IP, and then check its own internal ARP table again for the MAC address. Now, this would seem like a waste of resources compared to a router with a built-in switch. But maybe it does not work like that at all. Does it also contain a CAM table? If that would be true, what would then the difference between these two routers really be?

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• Why is REMOTE_ADDR only sometimes available as an Apache environment variable?

  - by Xiong Chiamiov

  To avoid having to parse X-Forwarded-For in Varnish, I'm trying to just set a header on the SSL terminator (currently Apache) that stores the direct client IP in a header. On our development machine, this works: RequestHeader set X-Foo %{REMOTE_ADDR}e However, in staging it doesn't. Specifically, the header is empty, as illustrated by both varnishlog: 13 TxHeader b X-Foo: (null) (On the development machine, this shows the IP address as expected.) Similarly, logging REMOTE_ADDR shows that it only appears to be populated on the dev machine: # Config LogFormat "%{X-Forwarded-For}i %{REMOTE_ADDR}e" combined CustomLog "/var/log/httpd/access_log" combined # Log file, staging <my ip> - # Log file, development <my ip> <my ip> Since the dev machine is, well, a dev machine, it is different in a number of ways; however, I can't track down which difference is causing this. The versions of Apache are the same (2.2.22), and I don't see anything relevant in any of the standard config files or /etc/sysconfig/httpd. And the rest of the system is reasonably similar, since they're built off the same CentOS 5 base image. I can't even tell from the Apache documentation whether REMOTE_ADDR is expected to exist or not as an environment variable, but it clearly works on one machine, whether by fluke or design, and the inconsistency is driving me mad.

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• What user information is exposed via a browser?

  - by ipso

  Is there a function or website that can collect and display ALL of the user information that can be obtained via a browser? Background: This of course does not account for the significant cross-reference abilities of large corporations to collate multiple sources and signals from users across various properties, but it's a first step. Ghostery is just a great idea; to show people all of the surreptitious scripts that run on any given website. But what information is available – what is the total set of values stored – that those scripts can collect from? If you login to a search engine and stay logged in but leave their tab, is that company still collecting your webpage viewing and activity from other tabs? Can past or future inputs to pages be captured – say comments on another website? What types of activities are stored as variables in the browser app that can be collected? This is surely a highly complex question, given to countless user scenarios – but my whole point is to be able to cut through all that – and just show the total set of data available at any given point in time. Then you can A/B test and see what is available with in a fresh session with one tab open vs. the same webpage but with 12 tabs open, and a full day of history to boot. (Latest Firefox & Chrome – on Win7, Win8 or Mint13 – although I'd like to think that won't make too much of a difference. Make assumptions. Simple is better.)

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• File Open/Save Dialog always 'Not Responding'

  - by Amanda

  I am aware that this question has been asked once, however the solution for them didn't work with me. Whenever I go to open/save a file in any program, the dialog does not come up, and the application goes to 'Not Responding'. This goes on for about a few minutes, and then stops, but still does not open the dialog. There have been a few occasions where the dialog has suddenly worked for a while, but then the problem comes back. I have tried many solutions given around the internet, I have cleaned it with CCleaner, disk defragged it, sorted the index. Nothing works. Is there anybody who has any idea what the problem is? This is Windows Vista. I'm not quite sure what kind of information you guys would need about my laptop, but I'll give you it if you need it. :) Solutions I have Tried: I have tried deleting the 'Shellicon' folder in the registry, which wasn't even in there. I have looked for mapped network drives lingering around, and I haven't come across any. I have tried rebuilding teh Widnows Search Indexes...no difference.

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• Scenario - NTFS Symbolic Link or Junction?

  - by Unsigned

  Differences Absolute Relative File Directory UNC Symbolic link ? ? ? ? ? Junction ? x x ? x Scenario Let's assume we're creating a reparse point to create the redirect C:\SomeDir => D:\SomeDir Since this scenario only requires local, absolute paths, either a junction or symlink would work. In this situation, is there any advantage to using one or the other? Assume Windows 7 for the OS, disregarding backward-compatibility (prior to Vista, symlinks are not supported). Update I have found another difference. Symbolic Link - Link's permissions only affect delete/rename operations on the link itself, read/write access (to the target) is governed by the target's permissions Junction - Junction's permissions affect enumeration, revoking permissions on the junction will deny file listing through that junction, even if the target folder has more permissive ACLs The permissions make it interesting, as symlinks can allow legacy applications to access configuration files in UAC-restricted areas (such as %ProgramFiles%) without changing existing access permissions, by storing the files in a non-restricted location and creating symlinks in the restricted directory.

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• Building vs buying a server for an academic lab [closed]

  - by Roy

  I'm looking for advice on the classic build vs buy question. We need a new linux server to run Matlab computation on in our lab (academic). Matlab parallel computing toolbox licence allows up to 12 local workers so we are aiming at a 12 core server with 4GB memory per core (total of 48gb). The system will have an SSD for the OS and a raid-5 (4x2tb) for data. I looked around and found a (relatively) cheap vendor, Silicon Mechanics, that offers a system to our liking (specs below) for $6732. However, buying the components from newegg cost only $4464! The difference is $2268 which is 50% of the base cost. If buying from a company can be thought of as a sort of insurance, basically my premiums are of 50% of the base cost which to me sounds like a lot. Of course any downtime is bad, but the work is not "mission critical", i.e. if it takes a few days to fix it when it breaks its no the end of the world. If it takes weeks to months then its a problem. If it breaks 2-3 times in 3 years, not too bad. If it breaks every month not good. In term of build experience, I set up a linux cluster in grad school (from existing computers) and I build my home pcs but I never built a server before. The server components I'm thinking about: 1 x SUPERMICRO SYS-7046T-6F 4U Tower Server Barebone Dual LGA 1366 Intel 5520 DDR3 1333/1066/800 ($1,050) 12 x Kingston 4GB 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) ECC Unbuffered Server Memory ($420) 2 x Intel Xeon E5645 Westmere-EP 2.4GHz LGA 1366 80W Six-Core ($1,116) 4 x Seagate Constellation ES 2TB 7200 RPM SATA 6.0Gb/s 3.5" ($1,040) 1 x SAMSUNG Internal DVD Writer Black SATA ($20) 1 x Intel 520 Series 2.5" 180GB SATA III MLC SSD $300 1 x LSI LSI00281 PCI-Express 2.0 x8 MD2 Low profile SATA / SAS MegaRAID SAS 9260CV-4i Controller Card, $695

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• User permissions linux. (proftpd / nginx)

  - by user55745

  I've been having a complete nightmare trying to configure proftpd. I've got proftp server working with an sql database. However I want to have any files uploaded able to viewed by the webserver running on the same box. The folders get created in /var/tmp/ as rwx------ 2 ftpuser ftpgroup 4096 Oct 8 20:35 50730c4346512 drwx------ 2 ftpuser ftpgroup 4096 Oct 8 20:38 50730f3a811ca I've tried adding www-data to group with the following usermod -g www-data ftpuser But this doesn't allow the web server access. In proftpd.conf I have the following umask set Umask 0022 It doesn't seem to make a difference what I set that value to. /etc/group (sure I've messed up one of these two but I'm getting desperate) ftpgroup:x:2001:www-data www-data:x:33:ftpgroup /etc/passwd www-data:x:33:33:www-data:/var/www:/bin/sh proftpd:x:108:65534::/var/run/proftpd:/bin/false ftp:x:109:65534::/srv/ftp:/bin/false ftpuser:x:2001:33:proftpd user www-data:/bin/null:/bin/false The ftpuser table in the database has uid / gid set to 2oo1 for both. I'm going absolutely crazy trying to solve this any help would be greatly appreciated. p.s Also, although if I manually connect to the ftp server I can upload files via FileZilla. Although this isn't working for the web-camera, although there is talky talky going on between the server and the camera.

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