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Search found 1451 results on 59 pages for 'theory'.

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• Which Wine DLLs should I *not* overwrite with the real thing?

  - by endolith

  I have a legit installation of Windows XP and dual boot with Ubuntu (currently Karmic). WineHQ says it's possible to use DLLs from a real installation of Windows in place of "DLLs that Wine does not currently implement very well". So I'd like to just create softlinks that point to all of the DLLs in my real Windows System32 folder, under the theory that this would help things function better and behave in a less buggy, more native way. But should I go as far as replacing the Wine DLLs with the real ones? If so, are there any DLLs that need to remain the way they are for compatibility with the Linux world? Which ones are safe to replace?

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• How to recover data from software RAID 5 disk partition

  - by Ali n

  I have CentOS 5.8 on my computer, with 5x 1TB hard drives. I used software RAID. (RAID 1 as a boot partition md0, RAID 0 as a root partition md1 and RAID 5 as /home partition md3). Unfortunately one of these hard drives failed lately and I want to replace it with a new one. I want to know that is it possible to change this hard drive without data loss? The important partition is RAID 5 so in theory if one of hard drives failed I should be able to recover its data without any problem. But in practice how can I do that?

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• Using Gentoo's `ebegin`, `eend` etc under Ubuntu

  - by Marcus Downing

  We're quite fond of the style of the ebegin, eend, eerror, eindent etc commands used by Portage and other tools on Gentoo. The green-yellow-red bullets and standard layout make for very quick spotting of errors, on what would otherwise be very grey command line output. #!/bin/sh source /etc/init.d/functions.sh ebegin "Copying data" rsync .... eend $? Producing output similar to: * Copying data... [ OK ] As a result we're using these commands in some of our common shell scripts, which is a problem for the people using Ubuntu and other linuxes. (linuces? linuxen? linucae? other distros) On Gentoo these functions are provided by OpenRC, and imported with functions.sh file (whose exact position seems to vary slightly). But is there a simple way of getting these commands on Ubuntu? In theory we could replace them all with dull echos, but we'd rather not?

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• How do UEFI and virtual machines relate to each other?

  - by Iterator

  I am trying to get my head around UEFI (Unified Extensible Firmware Interface) and it's not entirely clear to me how this affects virtual machines. Thus, there are three parts to this question: Is UEFI an advance in hardware support for virtualization? All other things being equal, would a machine with UEFI be more likely to run a virtual machine more efficiently than one without, or does UEFI cause any performance hits that negate any speed improvements from a virtual machine? Would the difference in execution be visible to code running in a virtual machine? (In theory, it shouldn't, but in practice?)

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• How can I improve performance over SMB/CIFS for an application that has poor write speeds?

  - by Jeremy

  I have a third party application that reads several large files and generates a third large file. Its performance is quite good when the generated file is stored on "local storage", i.e. either a direct attached or iSCSI-based disk. The source files that are read can be stored remotely on our NAS and accessed via SMB with little effect on performance. However, if we attempt to write the target file to any kind of SMB/CIFS share (Samba or Windows Server) the performance drops almost ten-fold. This is unacceptably slow in our case. Writing files to network shares is not otherwise slow. I can copy large files to SMB shares and get great performance - near what I would expect is possible given the disks and network in question. I have a theory that this application's problem with SMB shares has something to do with a lack of write caching over the share and perhaps lots of network roundtrips. Is this possible and is there anything that can be done about it?

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• Using "mv" or "ditto" to merge folders in OS X

  - by Sandro Dzneladze

  Used to the Windows way of doing I just found out OS X has no merge function – moving means replacing the folder. While this does make sense, I miss merging! I've two Wordpress directories, 1 contains default source and 2 contains worked version with plugins custom theme etc. I want to see difference between this two, so I'm putting it on SVN. Folder 1 is already up, now in theory I should simply merge contents of 2 with 1 by replacing everything with contents of 2 but leaving hidden SVN files untouched. Unfortunately OS X, when moving, replaces the folder so that my SVN client goes crazy and doesn't understand folder structure anymore. So, I believe my options are mv and ditto, but which one would you use in my situation and how? sudo mv wordpress /Documents/svn/wwwholiday/trunk/wordpress I want mv to overwrite everything it finds, but leave alone whatever is already inside folder 1 and has no duplicate in folder 2.

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• CPU Affinity on ARM processors

  - by dsljanus

  I am using some RaspberryPI boards for a data acquisition system. They are nice boards, with plenty of community support around them, but they are really slow. I am thinking of gradually replacing them with ODROID multicore boards, with the Samsung Exynos processors. I have some experience using taskset to set CPU affinity on my servers because I am always running Node.js applications that are by definition single threaded. Now, is it possible to do this on an ARM board? I do not see why it would not in theory, but I have doubts over how well it is going to work. Does anyone have experience with this kind of hack? Also, I would appreciate any comments about ARM CPUs and how they differ from x86.

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• How to tell if linux disk IO is causing excessive (> 1 second) application stalls

  - by noahz

  I have a Java application performing a large volume (hundreds of MB) of continuous output (streaming plain text) to about a dozen files a ext3 SAN filesystem. Occasionally, this application pauses for several seconds at a time. I suspect that something related to ext3 vsfs (Veritas Filesystem) functionality (and/or how it interacts with the OS) is the culprit. What steps can I take to confirm or refute this theory? I am aware of iostat and /proc/diskstats as starting points. Revised title to de-emphasize journaling and emphasize "stalls" I have done some googling and found at least one article that seems to describe behavior like I am observing: Solving the ext3 latency problem Additional Information Red Hat Enterprise Linux Server release 5.3 (Tikanga) Kernel: 2.6.18-194.32.1.el5 Primary application disk is fiber-channel SAN: lspci | grep -i fibre 14:00.0 Fibre Channel: Emulex Corporation Saturn-X: LightPulse Fibre Channel Host Adapter (rev 03) Mount info: type vxfs (rw,tmplog,largefiles,mincache=tmpcache,ioerror=mwdisable) 0 0 cat /sys/block/VxVM123456/queue/scheduler noop anticipatory [deadline] cfq

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• Tools for analyzing performance of SQL Server/Express?

  - by Adam Crossland

  The application that I have customized and continue to support for my client is seeing dramatic performance problems in the field. Simple queries on rather small datasets take over a minute when I would expect them to complete with sub-second times. My current theory is that SQL Server Express 2005 is too limited for the rather non-trivial demands being made of it, but I am not sure how to get about gathering data that I can use to either prove my point or allow me to move on to finding another cause. Can anyone point me toward some tools that would allow me to analyze the load on this database? Information such as simultaneous connections, execution times of individual queries, memory usage, heck just any profiling data at all would be a help. Many thanks.

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• Why can't I open my Access application in design mode?

  - by mmyers

  I have been given an Access 2007 application (mainly VB code) that I need to modify. It has been locked down for production, so the toolbars and so forth are not visible. However, it is a .mdb file, not .mde, so in theory it should be possible to get into design mode by holding Shift while opening it. But that method has only worked a total of three times out of the (probably) 60 or 70 times I've tried. I realize now that I should have enabled the toolbars while I had it open, but unfortunately hindsight doesn't get me anywhere now. Does anyone know what might be causing the problem? Is it my own fault, or the application's, or Access's?

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• How to put 1000 lightweight server applications in the cloud

  - by Dan Bird

  The company I work for sells a commercial desktop/server app that runs on any non dedicated Windows PC or server and uses Tomcat for all interactions with the application. Customers are asking that we host their instance of the application so they don't have to run it locally on their own servers. The app is lightweight and an average server, in theory, could handle 25-50 instances before users would notice a slowdown. However only 1 instance can run per Windows instance (because the application writes to a common registry branch) so we'd need something like VMWare to create 25-50 Windows instances. We know we eventually need to reprogram to make it truly cloud-worthy but what would you recommend for a server farm or whatever for this? We don't have the setup to purchase our own servers so we must use a 3rd party. We have budgeted $500 - $1000 per year per customer for this service. Thanks in advance for your suggestions, experiences and guidance.

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• Asus EEE PC 1005HA (XP Home) refuses to connect to Virgin Mobile MiFi

  - by Dennis Wurster

  My client has an Asus EEE PC model 1005HA, and we're attempting to connect it to the WiFi network created by a VirginMobile MiFi unit. They also have a MacBook Pro with Snow Leopard that has absolutely no issue connecting to the MiFi. The specific symptom is that the netbook fails to lease an IP address from the MiFi unit. I supply the 12-digit numerical password (WPA) to the netbook, it throws a 'waiting for network' dialog with an indeterminate progress indicator, and then times out. Update: We've determined that this behavior has stopped when the EEE PC and the MiFi unit were taken out of the client's home, and to a different home that didn't have an existing wifi network. Similarly, when taken to a third location that didn't have wifi, the EEE PC and MiFi got along swimmingly. My current theory is that the existing wifi networks and the wifi leg of the MiFi unit are on the same channel and competing with one another. Perhaps the MacBook Pro has the capability to overcome this interference, while the EEE PC doesn't.

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• LVM, Soft RAID1, and Replication?

  - by mtkoan

  Hi all, I am practicing putting together a HA file server. It is a linux server with 2 1.5TB Hard drives. My plan is to use LVM to manage the physical volumes into logical volumes for /, /home, and /var. Then use md (soft RAID 1) to mirror the image onto the second HDD, THEN use DRDB to mirror the entire setup another server. Is this overkill? Would I just be okay with just md and DRDB? The system will serve user's homedirs (~100) and probably some groupware or other local intranet. On my own machines I've always separated root and /home partitions in case I break something, I can easily reinstall the OS. Should I follow that same theory here? If so I need LVM, because I really can't predict where we'll need more space, /var or /home.

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• Using video ports 'backwards'

  - by ACarter

  If I want to connect my laptop, which has a VGA output, to a monitor, I plug a VGA cable into both ends. The output being my laptop, and the input the monitor VGA output sockets are the same as VGA input sockets however, so what if I want to use my laptop as the monitor, with the video being outputted from somewhere else? As I said, VGA's output is the same as input, so in theory, I have the hardware in my laptop to do this. But presumably I need some software. So can I use the VGA port on a laptop as a video input? (And also, can this be done with HDMI?)

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• Script errors when run by launchd at startup, but not when run in Terminal

  - by Mechcozmo

  I'm attempting to create a RAM disk that loads the previous contents when the system starts up, and every six hours writes the contents to a disk image. Currently, when you run the script from the terminal ("sudo bash LogToRAM.sh") everything works fine. But when run from launchd during startup, it doesn't work. Here's the lines from the log; the first line just gives some idea as to where in the boot process we are: SecurityAgent[202] Showing Login Window com.mechcozmo.LogToRAM[51] + /Developer/usr/bin/SetFile -a V /Volumes/LogfileRAMdisk com.mechcozmo.LogToRAM[51] ERROR: File Not Found. (-43) on file: /Volumes/LogfileRAMdisk com.mechcozmo.LogToRAM[51] + /usr/sbin/asr -source '/Library/Application Support/LogToRAM/RAMdisk_store.dmg' -target /Volumes/LogfileRAMdisk/ -noverify Here is the script and plist file in question. Note that 'set -vx' is up at the top of the script; it give a lot of information about what is happening in the script. My current theory is that the /Volumes directory does not exist at this stage of the boot process, but that seems unlikely to be honest.

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• installing SQLite3 gem on remote FreeBSD server using RVM - root permissions needed?

  - by atmosx

  I am trying to install ruby SQLite3 gem, on a remote freebsd server. I'm using RVM which in theory does not need 'root permission' to compile gems but I get a root error, here: [user ~]$ gem install sqlite3 -- --with-sqlite3-dir=/home/www/atma/opt/ [...] make install /usr/bin/install -c -o root -g wheel -m 0755 sqlite3_native.so /home/www/atma/.gems/gems/sqlite3-1.3.6/lib/sqlite3 install: /home/www/atma/.gems/gems/sqlite3-1.3.6/lib/sqlite3/sqlite3_native.so: chown/chgrp: Operation not permitted make: * [/home/www/atma/.gems/gems/sqlite3-1.3.6/lib/sqlite3/sqlite3_native.so] Error 71 Gem files will remain installed in /home/www/atma/.gems/gems/sqlite3-1.3.6 for inspection. Results logged to /home/www/atma/.gems/gems/sqlite3-1.3.6/ext/sqlite3/gem_make.out Any ideas how to approach this? Maybe re-installing RVM? best regards, PA

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• Anyone have any experience with bargain laptop batteries?

  - by chris

  I've got an oldish D820 that's got a 100% dead battery. I know that I could, in theory, take it apart and replace bad cells in the battery. I'm not really comfortable with doing that. I also know that there are various places that sell replacement batteries for 20% to 80% of the cost that Dell would charge. Does anyone have any experiences with buying more than a couple of these off-brand batteries? If a battery goes boom, it could be really ugly, so I'd rather not risk it, but at the same time, the dell batteries are really expensive... Any opinions on these ebay / off-brand battery vendors? Thanks!

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• How do I disable microphone volume auto-adjusting?

  - by balpha

  My coworkers started yelling at me today because apparently I started screaming in their ears during a Google hangout. And sure enough, when I go to the Microphone settings dialog, I can see the level being auto-adjusted constantly; sometimes way too high. I don't think this has happened previously; at least nobody ever complained. Can I find out who is doing that auto-adjusting, and more importantly, can I turn it off? I couldn't find any related setting in the recording device settings. I'm using Windows 7 64bit, and (I'm mentioning this because the theory has come up that it may be related) I don't have Skype running.

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• Preferred apache permissions for www files with several authors

  - by user1316464

  I can't for the life of me figure out how to design my permissions scheme for my apache files. My requirements seem pretty simple: Apache should have standard permissions of RX for Directories and R for files Web authors should have RWX for Directories and RW for files Don't want to give any access to "other" Want new files/folders to inherit the proper permissions Here are the schemes I've tried 570 for directories and 460 for files Owner: Apache Group: Webdev The problem here is that new files created by users int the Webdev group are owned by user:Webdev and Apache can't read them. If Apache were in the group Webdev then it would also have the wrong permissions (ie it would have Write permissions to files) 750 for directories and 640 for files Owner: Webdev Group: Apache (Webdev is a member of Apache) The problem here is that there is only one webdev account and I have multiple people who need access to contribute. In theory this would work with only one developer if Webdev were also a member of the Apache group. Any ideas?

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• SSH: one user logs in, other don't

  - by Co Lega

  Some users can ssh correctly, others don't. I have an admin user, which is in wheel. I used vsftpd for allowing FTP. I created a nologin user for FTP. Call this user "ftpuser". Now I want to allow sftp. It allows me to connect using admin user. I remove the nologin, by giving the user a shell via usermod -s /bin/bash ftpuser. It still doesn't allow me to connect from the ftpuser via sftp. The content of /home/ftpuser/.ssh is just the known_hosts file which contains "localhost" entry only. User permissions are (in theory) ok: ls -la /home working (admin) : drwx------ 18 admin admin 4096 Feb 6 15:33 admin non-working(ftpuser): drwx------ 3 ftpuser ftp 4096 Mar 26 15:25 ftpuser I haven't configured anything special on openssh. Does the ftpuser need anything extra than shell to enter via ssh?

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• Is visiting HTTPS websites on a public hotspot secure?

  - by Calmarius

  It's often said that HTTPS SSL/TLS connections are encrypted and said to be secure because the communication between the server and me is encrypted (also provides server authentication) so if someone sniffs my packets, they will need zillions of years to decrypt if using brute force in theory. Let's assume I'm on a public wifi and there is a malicious user on the same wifi who sniffs every packet. Now let's assume I'm trying to access my gmail account using this wifi. My browser does a SSL/TLS handshake with the server and gets the keys to use for encryption and decryption. If that malicious user sniffed all my incoming and outgoing packets. Can he calculate the same keys and read my encrypted traffic too or even send encrypted messages to the server in my name?

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• Cascading KVM switches

  - by einpoklum

  I have a not-so-small number of computers (say, 5) which I want to access with a single keyboard, USB and monitor. I can get an 8-port KVM switch, which is a pretty expensive piece of hardware; however, in theory, I should be able to cascade KVM switches: Have one 4-port KVM switch between 2 other KVMs (a 2-port and a 4-port). Is this doable (with typical off-the-shelf switches and cables)? Has anyone had experience doing this? Note: I'm interested in USB-only for the keyboard and mouse, and either VGA or DVI for the display. Audio and PS/2 connections are irrelevant for me..

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• How can I measure TCP timeout limit on NAT firewall for setting keepalive interval?

  - by jmanning2k

  A new (NAT) firewall appliance was recently installed at $WORK. Since then, I'm getting many network timeouts and interruptions, especially for operations which would require the server to think for a bit without a response (svn update, rsync, etc.). Inbound SSH sessions over VPN also timeout frequently. That clearly suggests I need to adjust the TCP (and ssh) keepalive time on the servers in question in order to reduce these errors. But what is the appropriate value I should use? Assuming I have machines on both sides of the firewall between which I can make a connection, is there a way to measure what the time limit on TCP connections might be for this firewall? In theory, I would send a packet with gradually increasing intervals until the connection is lost. Any tools that might help (free or open source would be best, but I'm open to other suggestions)? The appliance is not under my control, so I can't just get the value, though I am attempting to ask what it currently is and if I can get it increased.

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• Could a DNSSEC at level n manipulate a zone at level n+2?

  - by jroith

  With some people wondering how DNSSEC could affect global censorship, I'd like to know if DNSSEC could protect a zone from being partially modified by a grandparent zone. (The point of this question is not to suggest that ICANN or it's members are not be trusted, but to figure out how DNSSEC affects the power they could exercise in theory.) For example: ICANN owns the root zone The .de zone is delegated to DENIC, Germany. Assume example.de is delegated to some 3rd party. Now, assuming DENIC does not remove example.de from their zone, would it be possible for them to redirect the subdomain abc.example.de elsewhere by returning signed records from the .de servers for abc.example.de ? Similarly, would it be possible for the DNS root to easily return signed fake records of a third-level domain xy.z while the second-level zone z is not participating in this and is not affected otherwise?

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• Beast / CRIME / Beach attack and stopping it

  - by user2143356

  I have read so much on all this but not entirely sure I understand what has gone on. Also, is this one, two or three problems? It looks to me like three, but it's all very confusing: Beast CRIME Beach It seems the solution may be to simply not use compression with HTTPS traffic (or is that just on one of them?) I use GZIP compression. Is that okay, or is that part of the problem? I also use Ubuntu 12.04 LTS Also, is non-HTTPS traffic okay? So after reading all the theory I just want the solution. I think this may be the solution, but can someone please confirm I have understood everything so I am not likely to suffer from this attack: SOLUTION: Use GZIP compression on HTTP traffic, but don't use any compression on HTTPS traffic

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