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• ISCSI: Ethernet cable maximum length vs. SCSI command timeout

  - by Jeremy Hajek

  I have a question about a non-optimal setup and the practical implications of this. Ideally you would place the ESXi server right in the same room as the FreeNas white box end of question. My situation is this: I have a run of ~125ft of Cat 5e connecting a ESXi server to a FreeNas whitebox in the server room. I know the distance of the ethernet cable is within the maximum distance for ethernet traffic but I have two questions... Can Cat 5e support gigbit speeds at that distance if the switch on the back end is a linksys SRW-2048? Should I be concerned about the distance causing data read and write timeouts in the SCSI portion--(disk operations of the ESXi)?

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• SonicWall HA "gotchas"?

  - by Mark Henderson

  We're looking to move away from PFSense and CARP to a pair of SonicWall NSA 24001 configured in Active/Passive for High Availability. I've never dealt with SonicWall before, so is there anything I should know that their sales guy won't tell me? I'm aware that they had an issue with a lot of their devices shutting down connectivity because of a licensing fault, and they have an overtly complex management GUI (on the older devices at least), but are there any other big "gotchas" that I need to be aware of before committing a not insubstantial amount of money towards these devices? 1If you're outside the US, the SonicWall global sites suck balls. Use the US site for all your product research, and then use your local site when you're after local information.

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• Disk is apparently in use by the system

  - by Shaun

  I've just fitted two disks to my home server. I'm trying to format and then raid them but I'm getting a problem that hours of Googling hasn't resolved this. The error that I'm getting is: # mkfs.ext3 /dev/sdb1 mke2fs 1.39 (29-May-2006) /dev/sdb1 is apparently in use by the system; will not make a filesystem here! # df -h Filesystem Size Used Avail Use% Mounted on /dev/sda1 4.0G 1.9G 2.0G 49% / none 380M 0 380M 0% /dev/shm /opt/xensource/packages/iso/XenCenter.iso 51M 51M 0 100% /var/xen/xc-install # mount -t ext3 /dev/sdb1 /mnt/b mount: /dev/sdb1 already mounted or /mnt/b busy I'm new to this and it's got me beat. I wouldn't ask if I hadn't done my research first. Thanks.

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• WBAdmin SystemState Problems

  - by TheD

  I recently installed DHCP on my 2008R2 Server and now Backup Exec and WBAdmin/WSB is having System State issues. Essentially, after some research, I came across a handy tool called VSHADOW which has allowed me to output all the files (and their respective directories) to a text file. And hooray, I think I found the problem: * WRITER "Dhcp Jet Writer" - WriterId = {be9ac81e-3619-421f-920f-4c6fea9e93ad} - InstanceId = {0ed0a8f4-19b0-414d-a3a8-d51d6f4ac8e0} - Supports restore events = TRUE - Writer restore conditions = VSS_WRE_IF_REPLACE_FAILS - Restore method = VSS_RME_RESTORE_AT_REBOOT - Requires reboot after restore = TRUE - Excluded files: - Component "Dhcp Jet Writer:\C:_Windows_system32_dhcp\dhcp" - Name: 'dhcp' - Logical Path: 'C:_Windows_system32_dhcp' - Full Path: '\C:_Windows_system32_dhcp\dhcp' The logical path and Full Path for DHCP is completely wrong. However I can't find where I would change this path, I assume in the registry but I've had no luck finding the key !

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• DNS Server (2008 r2) MMC The server DC01 could not be contacted. The error was: Access was denied

  - by Silviu-Ionut Radu

  I've just migrated the AD with the whole nine yards, FSMO, PDC, RID, Schema, etc, from an SBS 2003 to a Win 2008 R2 Std. I have managed to have no error in the dcdiag before I demoted the SBS 2003 from the AD, fsmocheck, conectivity, advertising, dns, etc. The SBS 2003 demoted successfully. After this step I have restarted both, the old SBS and the new Win 2008 r2. After restart the new DC (which is the GC) started with an Access denied to the DNS Server MMC, actually it is looking like I would try to connect to the 2008 r2 DNS server from an older server console I can NOT manage DNS server through MMC nor through dnscmd (Command failed: ERROR_ACCESS_DENIED 5 0x5) I cannot even use the Action Option from the DNS Server MMC because all the options are DISABLED but for "Launch nslookup". I've made a lot of research on the internet but no luck, yet. So I come to ask for help. Thank you very much.

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• Recommended integration mechanism for bi-directional, authenticated, encrypted connection in C clien

  - by rcampbell

  Let me first give an example. Imagine you have a single server running a JVM application. This server keeps a collection of N equations, once for each client: Client #1: 2x Client #2: 1 + y Client #3: z/4 This server includes an HTTP interface so that random visitors can type https://www.acme.com/client/3 int their browsers and see the latest evaluated result of z/4. The tricky part is that either the client or the server may change the variable value at any time, informing the other party immediately. More specifically, Client #3 - a C app - can initially tell the server that z = 20. An hour later that same client informs the server that z = 23. Likewise the server can later inform the client that z = 28. As caf pointed out in the comments, there can be a race condition when values are changed by the client and server simultaneously. The solution would be for both client and server to send the operation performed in their message, which would need to be executed by the other party. To keep things simple, let's limit the operations to (commutative) addition, allowing us to disregard message ordering. For example, the client seeds the server with z = 20: server:z=20, client:z=20 server sends {+3} message (so z=23 locally) & client sends {-2} message (so z=18 locally) at the exact same time server receives {-2} message at some point, adds to his local copy so z=21 client receives {+3} message at some point, adds to his local copy so z=21 As long as all messages are eventually evaluated by both parties, the correct answer will eventually be given to the users of the client and server since we limited ourselves to commutative operations (addition of 3 and -2). This does mean that both client and server can be returning incorrect answers in the time it takes for messages to be exchanged and processed. While undesirable, I believe this is unavoidable. Some possible implementations of this idea include: Open an encrypted, always on TCP socket connection for communication Pros: no additional infrastructure needed, client and server know immediately if there is a problem (disconnect) with the other party, fairly straightforward (except the the encryption), native support from both JVM and C platforms Cons: pretty low-level so you end up writing a lot yourself (protocol, delivery verification, retry-on-failure logic), probably have a lot of firewall headaches during client app installation Asynchronous messaging (ex: ActiveMQ) Pros: transactional, both C & Java integration, free up the client and server apps from needing retry logic or delivery verification, pretty straightforward encryption, easy extensibility via message filters/routers/etc Cons: need additional infrastructure (message server) which must never fail, Database or file system as asynchronous integration point Same pros/cons as above but messier RESTful Web Service Pros: simple, possible reuse of the server's existing REST API, SSL figures out the encryption problem for you (maybe use RSA key a la GitHub for authentication?) Cons: Client now needs to run a C HTTP REST server w/SSL, client and server need retry logic. Axis2 has both a Java and C version, but you may be limited to SOAP. What other techniques should I be evaluating? What real world experiences have you had with these mechanisms? Which do you recommend for this problem and why?

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• Making python run on my webserver

  - by richzilla

  Hi all, im getting a bit stuck regarding options for running python scripts on my server. From the research ive done so far, i can see i need to modify apache slightly to run python scripts, by using either mod_wsgi or mod_python. Two issues i have: mod_python doesnt appear to be maintained anymore (last release, 2007) mod_wsgi appears to require modification of my httpd.conf file on a per application basis. What im wanting to know, is there a way of getting python scripts to run in the same way as php, i.e. just by going to index.py etc... or is it more involved than that? At present im just trying to set it up on my xampp install. Any help would be appreciated.

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• Do you have suggestions for these assembly mnemonics?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• Apple file sharing: bind to a specific interface

  - by Cesar

  My customer have an office small office with just a wifi router. He use this router for internet connectivity and file transfer operations between the desktops. Recently the file transfer activity between desktop (all osx based) is increased a lot so he bought a switch (no connected to the router, too far away) for transfer the file over the cable instead over the wifi. Problem: How to bind the file sharing service just to the Ethernet interface and exclude the wifi interface ? (actually the service binds to the wifi automatically and there are no options about the interface binding)

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• I installed DKIM and SPF. Do I need to install Domain Keys as well?

  - by johnlai2004

  I have linux apache mysql and php server. My website uses the php mail() function and the server's postfix server to email other people. I successfully installed SPF and DKIM on my server to reduce the likelihood of my website's email-outs from ending up in people's spam boxes. In my research, I stumbled on Domain Keys which seems to be a "historical" version of DKIM. Do the big web mail services like Google, Yahoo and Hotmail still use Domain Keys? If not, then maybe I don't need to install it?

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• What does % mean in linux / how to install jmf

  - by Ben

  I am fairly new to linux and am using fedora 14 (64 bit). I have to install the java media framework for one of my projects. In the installation instructions on their website (http://www.oracle.com/technetwork/java/javase/download-142937.html) they use the % symbol. I have done some research and googling and can't find what the significance of % is. Does anyone know? I have been able to find just about every other symbol meaning (., .., #, and more). They use it in the following context Run the command % /bin/sh ./jmf-2_1_1e-linux-i586.bin

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• Is giving read permissions on /etc/shadow to apache user a wise decision from security point of view?

  - by Czar

  I have to use PAM authentication for DAV SVN, but when everything is configured as specified in mod_auth_pam documentation, authentication does not work. After some research I realized, that for this to work, httpd should be running under root user (which I don't like and won't implement) or apache user (under which httpd is running by default) should have permissions to read /etc/shadow file. So there is a pair of questions connected to each other which I want to ask: Is giving this permition to apache user a wise decision from security point of view? If answer to the first question is "yes", what is the correct way to do so? For now I've done following: groupadd shadow usermod -G shadow apache chmod g+r /etc/shadow Another way I can come up with is using acl: setfacl -m u:apache:r /etc/shadow Note: OS is Fedora 14 x86_64 (kernel: 2.6.35.11) httpd v2.2.17 mod_auth_pam v1.1.1

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• How do I log file system read/writes by filename in Linux?

  - by Casey

  I'm looking for a simple method that will log file system operations. It should display the name of the file being accessed or modified. I'm familiar with powertop, and it appears this works to an extent, in so much that it show the user files that were written to. Is there any other utilities that support this feature. Some of my findings: powertop: best for write access logging, but more focused on CPU activity iotop: shows real time disk access by process, but not file name lsof: shows the open files per process, but not real time file access iostat: shows the real time I/O performance of disk/arrays but does not indicate file or process

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• How do I log which process is deleting a file on Windows XP?

  - by Jordan Milne

  I'm having an issue with a file getting deleted seemingly randomly throughout the day. The vendor of the software whose file is getting deleete says that another piece of software installed on the computer is deleting it, while the other software's vendor says the opposite. I've tried using Process Monitor so I can pinpoint exactly what's deleting it, but even when filtered specifically to that file, createfile operations are being triggered a few times a second, and I can't seem to filter it to deletions specifically. Is there a tool or script I can use to specifically monitor deletion attempts on a single file?

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• Missing disk space in Windows XP

  - by Jørn Schou-Rode

  On my mother's Lenovo laptop, Windows XP claims that the hard drive is almost full. According to the properties window, 52.7 out of 55.2 GB is in use: By deleting temp files from Internet Explorer, System Restore, Recycle bin, Windows Update, System Cleanup, I managed to free up about one GB. That's still 50 GB in use, which still is a lot more than I expected. Hence, I gave good old WinDirStat a spin, and here's the output: It might be hard to read here, but the first line says that the total amount of disk space in use on drive C is 24.3 GB. So Windows claims usage of 52.7 GB and WinDirStat can only account for 24.3 GB. Where is the other half of that disk space being used? I hope someone has an answer, or some tricks or tips to do further research. UPDATE: The laptop in question has an SSD hard drive. I am aware that these disk (at least the earlier ones) have a limited life-time. Could the symptoms described be caused by wear and tear on the SSD?

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• SEAGATE Barracuda 7200.11 HDD not running

  - by Dane411

  After a huge research, I'm stuck at the beggining of getting my HDD data back. Whats happening to me is that in the moment when I plug the power wire to my external 1TB SEAGATE Barracuda 7200.11 ST31000333AS HDD Fw LC15, it makes the sound like it's spinning to almost full speed and then shuts down and spins up again, and so on. It's well known that those HDDs have a bad firmware that someday randomly fails. There are like 2 main problems identified, BSY (busy) state, and LBA0 error. Last time I connected it to power nothing happened, it didnt try to start at all, is it that so called bricked state? I guess my HDDs error is the first one, but I dont really know if what I described is that BSY state or not, neither I know how to check it. How could I know it? Thank you so much!

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• Large file copy from NFS to local disk performance drop

  - by Bernhard

  I'm trying to copy a 200GB file from an NFS mount to a local disk. The local disk is an XFS filesystem on a LVM on top of a RAID 5 system (hardware RAID controler). I'm using rsync to monitor the transfer speed. At the beginning the IO speed is about 200MB/s, stable for the first 18GB. But then the performance drops by a factor of 10-20 and never recovers to the initial rate. Sometimes it reaches about 50-100MB/s but just for a few seconds and then the process seems to hang for a bit. At the same time all file-stat operations on the target filesystem are blocking for a long time (minutes). Also interrupting the copy process blocks for several minutes, a sub-sequent delete of the partly copied file takes also several minutes. Any ideas what could be causing this?

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• How to share malicious source code?

  - by darma

  I have a client whose site (not one i developed) is infected by a trojan/malicious code. I have asked him to send me the dirty files in a zip but either gmail or unzipping is blocking them. I've tried text files and word files, and i'm suspecting many different file types will be blocked the same way, either by my mail client, anti-malware software, browser etc. (which is normal). Do you know a way he could share those lines so i can read them and do some research about the malicious source code? An image/screenshot of his text editor would be an idea but the files are long + i'd prefer to be able to copy/paste from them. Thank you!

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• Video on demand streaming solution

  - by Rafal Saltarski

  we are looking into building a commercial vod service and I'm doing research on the subject. We need the video to be protected with DRM so users cant rip/copy (i realise its mostly useless but the lawyers demand it from us) and the server solution to be scalable and able to distrubute content in hd to a high number of clients. Besides, we would need to be able to develop a player integrated with the payment system, so users that havent bought access would for example only see the first 30 seconds of video and then have the playback interrupted, or only be able to watch video for 72h after payment. Also it would be nice if we could distribute video to mobile platforms like android/wp8/ios but thats not a priority at the moment. I have zero experience on that topic so I would greatly appreciate any feedback or giving me stuff to read about like protocols or key phrases i should know. Thanks

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• Want 2 external monitors with a 13' MacBook - is this possible?

  - by kevinburke

  I've got a 13' white MacBook from 2008 and I'd like to run one or two external monitors, my budget is $500. I've tried to do research and this is what I was going to get - will these work OK? Two Diamond BVU195 HD USB Display Adapters (DVI and VGA with included DVI to VGA adapter) to plug into the USB port Two Dell ST2310 monitors One external USB hub so I don't use up both of my USB ports Will this work? I've read some people say it does and some people say it doesn't, but I don't know enough to say either way. Also do you have recommendations for a better monitor than the dell sd2310? what's the best setup I can buy for $500? Thanks very much for your help, Kevin

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• Postfix - Block email from non-existent local addresses

  - by Kelso.b

  My question is very similar to this one, but for postfix. We keep getting emails from addresses like "[email protected]" delivered to other "@ourdomain.com" addresses. From my google research, I understand it might not be practical to verify the email originated from our IP or VPN (Although this would be ideal, so if you can think of a way to do this, let me know), but in most of these cases the sender address (ex. "accounting") is not a valid account. I imagine there must be a way to make sure that a local account exists before delivering the message.

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• NT4 server generate too much weird DNS queries, How can i see the source PID?

  - by Hanan N.

  I have a NT4 server that in the last two weeks started to generate too many weird DNS queries to the DNS server is set to use. I have got warnings from the IPS system that it has blocked the responses from the DNS server back to the NT4 server. The queries it generate doesn't relate to any computer in the network, it is like 120624100088.xxxxxxx.net where xxx is the internal network, the numbers are just random at each query. I have done some research on how to get the PID that is generating the queries, and i found that only Process Monitor could give me that information, but since it is NT4 system Process Monitor doesn't work on it. It is a production server and i am just can't stop services as i want. I would like to get your advice on how can i get the PID that is generating these queries? Thanks.

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• Speed up file access on home network

  - by kurasa

  I have 2 PCs (Windows 7 Ultimate) and a Mac running Windows 7 using vmware fusion on my home network tied together using WRN1000 NETGEAR Router On one of the PC's I have a set of file (MYOB .myo). These use a data source to access the data in the files. Operations (reading,writing) to the .myo on the PC which hosts the files is fine but the other 2 it is painfully slow/unreliable and I am wondering what I can do to speed this up. Some ideas I have are 1. Turn off the Windows firewall on all the windows installations on the home network 2. Buy another router. Specifically a router which I can connect a USB flash drive on the back where I can put the .myo files and all the PC can access the files from the USB flash drive on the router (does this speed things up?) Any advice greatly appreciated on how I can speed up this access to data

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• Windows 7 just restarts, no BSOD, shows "Event ID 14 volsnap"

  - by Mdc007

  My Windows 7 just restarts without giving me a BSOD. When it reboots, it will hang sometimes and you have to let it rest. Sometimes it will print a message saying that Hal.dll is missing or corrupt. When it does restart I can't run a backup or a clone drive – it comes up with constant errors. I tried to run chkdsk – it says everything's clean. What is really puzzling is SyncToy on a different drive hangs half way through and won't run either. Machine: OCZ SSD Agility 2 for C drive SATA HDD for programs, documents on D drive MSI AMD 880 chipset Event viewer says something about critical power failure I/O operations and "Event ID 14 volsnap" – but that is just telling me the computer powered off which I already know.

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• Looking at desktop virtualization, but some users need 3D support. Is HP Remote Graphics a viable solution?

  - by Ryan Thompson

  My company is looking at desktop virtualization, and are planning to move all of the desktop compute resources into the server room or data center, and provide users with thin clients for access. In most cases, a simple VNC or Remote Desktop solution is adequate, but some users are running visualizations that require 3D capability--something that VNC and Remote Desktop cannot support. Rather than making an exception and providing desktop machines for these users, complicating out rollout and future operations, we are considering adding servers with GPUs, and using HP's Remote Graphics to provide access from the thin client. The demo version appears to work acceptably, but there is a bit of a learning curve, it's not clear how well it would work for multiple simultaneous sessions, and it's not clear if it would be a good solution to apply to non-3D sessions. If possible, as with the hardware, we want to deploy a single software solution instead of a mishmash. If anyone has had experience managing a large installation of HP Remote Graphics, I would appreciate any feedback you can provide.

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