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• Google Apps: MX records for zonefile

  - by 23tux

  Hi everybody, I have a question about using Google Apps for handling emails. I don't want to set up a whole entire mail system on my server, so I decided to use Google Apps. The ownership of my domain is approved, and now I'm trying to change the MX records in the zone file of my domain. But I think I'm doing wrong, it doesn't work. I want to use mail.mydomain.com as a adress to the mail server for POP, SMTP and IMAP. My zone file looks like this: $TTL 86400 @ IN SOA ns1.first-ns.de. postmaster.robot.first-ns.de. ( 2011011700 ; serial 14400 ; refresh 1800 ; retry 604800 ; expire 86400 ) ; minimum @ IN NS robotns3.second-ns.com. @ IN NS robotns2.second-ns.de. @ IN NS ns1.first-ns.de. @ IN A 111.111.111.111 localhost IN A 127.0.0.1 www IN A 111.111.111.111 ftp IN CNAME www loopback IN CNAME localhost mail IN CNAME @ relay IN CNAME www @ IN MX 10 ALT1.ASPMX.L.GOOGLE.COM. @ IN MX 10 ASPMX3.GOOGLEMAIL.COM. @ IN MX 10 ASPMX2.GOOGLEMAIL.COM. @ IN MX 10 ASPMX.L.GOOGLE.COM. @ IN MX 10 ALT2.ASPMX.L.GOOGLE.COM. I hope someone can figure out, what's wrong with this configuration. When I start a ping on mail.mydomain.org I get an answer from 111.111.111.111 and not from the google server ALT1.ASPMX.L.GOOGLE.COM. thx, tux

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• BackupExec 12 + RALUS - VERY slow backups

  - by LVDave

  We use Backup Exec 12 and the Remote Agent for Linux/Unix Servers (RALUS) to backup a large RHEL5 system. For various reasons we need to do a daily working set job. These working-set jobs run abysmally slow. The link between the target machine and the BE server is gigabit, and any other type of job runs 1-3GB/min. These working-set jobs start out at perhaps 40MB/min and over the course of the backup job slowly drops down so low that the BE job rate display in the "current jobs" goes blank.. Since we usually are only doing changed-files for one day, the job is usually small and finishes overnight and we don't worry abotu the slowness, but we had some issues with the backup server, and missed about 6 days of fairly heavy work on the Linux box, so this working-set job will be a doozy.. We have support with Symantec, and I've pestered them a lot about this, they've had me run RALUS in debug mode, sent them that log and a VXgather from the BE host and they had no fix/workaround.. To give an idea, I have the mentioned working-set job running for the last 3 1/2 hours and it's backed up just under 10MEGAbytes.... I'm posting this here to see if anybody in the "real world" has seen this/and/or has any ideas what might be causing these abysmally slow jobs, since Symantec seems to be clueless...

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• Safe use of Update-FormatData?

  - by Steve B

  In a custom PowerShell module, I have at the top of my module definition this code: Update-FormatData -AppendPath (Join-Path $psscriptroot "*.ps1xml") This is working fine as all .ps1xml files are loaded. However, the module is sometimes loaded using Import-Module MyModule -Force (actually, this is in the install script of the module). In this case, the call to Update-FormatData fails with this error : Update-FormatData : There were errors in loading the format data file: Microsoft.PowerShell, c:\pathto\myfile.Types.ext.ps1xml : File skipped because it was already present from "Microsoft.PowerShell". At line:1 char:18 + Update-FormatData <<<< -AppendPath "c:\pathto\myfile.Types.ext.ps1xml" + CategoryInfo : InvalidOperation: (:) [Update-FormatData], RuntimeException + FullyQualifiedErrorId : FormatXmlUpateException,Microsoft.PowerShell.Commands.UpdateFormatDataCommand Is there a way to safely call this command? I know I can call Update-FormatData with no parameters, and it will update any known .ps1xml file, but this would work only if the file has already been loaded. Can I list somewhere the loaded format data files? Here is a bit of background: I'm building a custom module that is installed using a script. The install script looks like : [CmdletBinding(SupportsShouldProcess=$true,ConfirmImpact="High")] param() process { $target = Join-Path $PSHOME "Modules\MyModule" if ($pscmdlet.ShouldProcess("$target","Deploying MyModule module")) { if(!(Test-Path $target)) { new-Item -ItemType Directory -Path $target | Out-Null } get-ChildItem -Path (Split-Path ((Get-Variable MyInvocation -Scope 0).Value).MyCommand.Path) | copy-Item -Destination $target -Force Write-Host -ForegroundColorWhite @" The module has been installed. You can import it using : Import-Module MyModule Or you can add it in your profile ($profile) "@ Write-Warning "To refresh any open PowerShell session, you should run ""Import-Module MyModule -Force"" to reload the module" Import-Module MyModule -Force Write-Warning "This session has been refreshed." } } MyModule defines, as first statement, this line : Update-FormatData -AppendPath (Join-Path $psscriptroot "*.ps1xml") As I updated my $profile to always load this module, the Update-Path command has been called when I run the install script. In the install script, I force import the module, which be fire again the module, and then, the Update-Path call

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• nginx with fail2ban and mod_security

  - by Mahesh

  I forgot to update my fail2ban config for nginx. I just moved to nginx from apache. Today, I got a lot of cals from a single IP. IP tried to access login pages with post and get methods IP tried to use nginx as a proxy (GET http:/...) IP searched images, js, css folders IP tried to inject -d url_allow_fopen =1 and something similar. Most of the calls ended with 404. http { limit_req_zone $binary_remote_addr zone=app:10m rate=5r/s; ... server { ... location / { limit_req zone=app burst=50; } I got approximately 50 requests from that ip for a second. So i updated my nginx like the above. Will it avoid too many connections per second now? I have updated my fail2ban jail.local to support nginx. I am confused with the nginx-noscript.conf [Definition] failregex = ^<HOST> -.*GET.*(\.php|\.asp|\.exe|\.pl|\.cgi|\scgi) ignoreregex = I am serving php with nginx. I checked apache's noscript.conf and which has .php extension on it too. I tested this above settings before restarting fail2ban and got thousands of ips matched. I removed php and nothing matched. Do i need .php| in nginx-noscript.conf? Using mod_security and fail2ban together bring any problem? When i was searching today, i came to know mod_security is available for nginx too. So i am planning to use it too.

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• HAProxy, health checking multiple servers with different host names

  - by Marco Bettiolo

  I need to load balance between multiple running servers with different host names. I cannot set-up the same virtual host on each one. Is it possible to have only one listen configuration with multiple server and make the Health Checks apply the http-send-name-header Host directive? I am using HAProxy 1.5. I came up with this working haproxy.cfg, as you can see, I had to set a different hostname for each health check as the health check ignores the http-send-name-header Host. I would have preferred to use variables or other methods and keep things more concise. global log 127.0.0.1 local0 notice maxconn 2000 user haproxy group haproxy defaults log global mode http option httplog option dontlognull retries 3 option redispatch timeout connect 5000 timeout client 10000 timeout server 10000 stats enable stats uri /haproxy?stats stats refresh 5s balance roundrobin option httpclose listen inbound :80 option httpchk HEAD / HTTP/1.1\r\n server instance1 127.0.0.101 check inter 3000 fall 1 rise 1 server instance2 127.0.0.102 check inter 3000 fall 1 rise 1 listen instance1 127.0.0.101:80 option forwardfor http-send-name-header Host option httpchk HEAD / HTTP/1.1\r\nHost:\ www.example.com server www.example.com www.example.com:80 check inter 5000 fall 3 rise 2 listen instance2 127.0.0.102:80 option forwardfor http-send-name-header Host option httpchk HEAD / HTTP/1.1\r\nHost:\ www.bing.com server www.bing.com www.bing.com:80 check inter 5000 fall 3 rise 2

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• pdns-recursor allocates resources to non-existing queries

  - by azzid

  I've got a lab-server running pdns-recursor. I set it up to experiment with rate limiting, so it has been resolving requests openly from the whole internet for weeks. My idea was that sooner or later it would get abused, giving me a real user case to experiment with. To keep track of the usage I set up nagios to monitor the number of concurrent-queries to the server. Today I got notice from nagios that my specified limit had been reached. I logged in to start trimming away the malicious questions I was expecting, however, when I started looking at it I couldn't see the expected traffic. What I found is that even though I have over 20 concurrent-queries registered by the server I see no requests in the logs. The following command describes the situation well: $ sudo rec_control get concurrent-queries; sudo rec_control top-remotes 22 Over last 0 queries: How can there be 22 concurrent-queries when the server has 0 queries registered? EDIT: Figured it out! To get top-remotes working I needed to set ################################# # remotes-ringbuffer-entries maximum number of packets to store statistics for # remotes-ringbuffer-entries=100000 It defaults to 0 storing no information to base top-remotes statistics on.

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• Does having TRIM enabled affect other hard drives on a computer (and how do you know when Windows is using it)?

  - by Breakthrough

  I recently purchased a solid state drive (an OCZ Vertex 2 (80 GB)) to use as my primary operating system partition. I also have three other SATA hard drives of assorted sizes. I successfully installed Windows 7 Professional onto the SSD (works awesome, great response time and transfer rate), and used the other three HDDs for data storage. I was browsing through the Bible of OCZ SSDs, and noticed the following in Section 60-76 - Tweaks and TRIM: Q. How do I know if TRIM is enabled on my OCZ SSD? A. In Windows 7, go to start/run/cmd), type the following: fsutil.exe behaviour query DisableDeleteNotify It should respond back with: DisableDeleteNotify=0 if TRIM support is ready and active. If it's not, then type: fsutil.exe behavior set DisableDeleteNotify 0 After a bit of searching on Google, I found similar results elsewhere (set DisableDeleteNotify to 0, which makes sense since for TRIM to work, the solid-state drive needs to be notified when deletes occur (for the garbage collector) unlike a normal hard drive). When I run the query on fsutil, I get the following result: DisableDeleteNotify = 48 Following the instructions I found, I set this to 0 instead of 48. However, I am beginning to wonder. Is this all the proof I really need that the OS is using TRIM? Also, since this applies globally for the computer, is TRIM data being sent to the other hard drives connected to the computer? And if so, would this cause any degradation in disk performance?

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• What does SQL Server's BACKUPIO wait type mean?

  - by solublefish

  I'm using Sql Server 2008 ("R1"), with some maintenance plans that back up my databases to a network share. Some of my backup jobs show long waits of type "BACKUPIO". Of course it seems like this is an I/O subsystem limitation, but I'm skeptical. Perfmon stats for I/O on the production (source) server are well within normal trends for that server. The destination server shows a sustained 7MB/s write rate, which seems incredibly low, even for a slow disk. The network link is gigabit ethernet and nowhere near saturated. The few docs I've turned up about BACKUPIO indicate that it's not specifically a wait on I/O, surprisingly enough. This MSFT doc says it's abnormal unless you're using a tape drive, which I'm not. But it doesn't say (or I don't understand) exactly what resource is missing. http://www.docstoc.com/docs/24580659/Performance-Tuning-in-SQL-Server-2005 And this piece says it's not related to I/O performance at all. http://www.informit.com/articles/article.aspx?p=686168&seqNum=5 "Note that BACKUPIO and IO_AUDIT_MUTEX are not related to IO performance." Anyway, does anyone know what BACKUPIO actually means and/or what I can do to diagnose or eliminate it?

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• Frequency of RAM

  - by Vignesh Palani

  I have a very old system hp compaq dx2080. It had 1gb of RAM. I recently bought a EVM DDR2 1 GB PC RAM which had a clock rate of 667Mhz. I have dual booting windows 7 and 8. When I installed it, windows 7 was still using the older 1gb. It showed as 2 gb available and 1gb usable in system properties. I searched around and found that I can change it to max in the msconfig. I did so. I set it 2048. Still, it was using only 1gb. When, I switched to 8, it was using the 2gb. Now, for my question: My system only supported 553Mhz and 667Mhz RAM. In the BIOS, I saw that the new RAM was showing as 800Mhz. Rechecked using speccy and cpu-z. It showed different values between the two. The RAM is labeled as 667Mhz over it. No mistake in that. But, am I missing something? Please help. And, can I continue using it? My point again. There are only two slots.

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• Strategy for Incremental Datasource fetchings in Excel

  - by user1352530

  I am in an scenario with a table that is refresh by a third app every week. I need to keep accumulating all data in Excel, using an ODBC connection to the database. I am wondering Approach 1: Is there a way to force Excel to append results for every update (this update would be triggered according to a parameter that indicates week)? I tried to define the table for which the connection loads using a dynamic reference but once is anchored first time, table position is never redefined Approach 2: Use an ETL to accumulate all weekly results into a staging table and then connect Excel to it in real time. But, I would need a mechanism for caching old data, as I cannot grow exponentially the time Excel opens. Imagine after 10 years, Excel would need to update at opening 10 years fo data before showing it. Is there a way to store already fetched data and increment it at real time (when book is opened) by selecting new data (with a query/filter of something) Thanks EDIT: Maybe it's better to ask it that way: What is the optimal strategy for a table that keeps growing and needs to be read in real time by Excel? I just don't want to fetch absolutely all data after some months...

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• Linux iptables / conntrack performance issue

  - by tim

  I have a test-setup in the lab with 4 machines: 2 old P4 machines (t1, t2) 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t3) Intel e1000 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t4) Intel e1000 to test linux firewall performance since we got bitten by a number of syn-flood attacks in the last months. All machines run Ubuntu 12.04 64bit. t1, t2, t3 are interconnected through an 1GB/s switch, t4 is connected to t3 via an extra interface. So t3 simulates the firewall, t4 is the target, t1,t2 play the attackers generating a packetstorm thorugh (192.168.4.199 is t4): hping3 -I eth1 --rand-source --syn --flood 192.168.4.199 -p 80 t4 drops all incoming packets to avoid confusion with gateways, performance issues of t4 etc. I watch the packet stats in iptraf. I have configured the firewall (t3) as follows: stock 3.2.0-31-generic #50-Ubuntu SMP kernel rhash_entries=33554432 as kernel parameter sysctl as follows: net.ipv4.ip_forward = 1 net.ipv4.route.gc_elasticity = 2 net.ipv4.route.gc_timeout = 1 net.ipv4.route.gc_interval = 5 net.ipv4.route.gc_min_interval_ms = 500 net.ipv4.route.gc_thresh = 2000000 net.ipv4.route.max_size = 20000000 (I have tweaked a lot to keep t3 running when t1+t2 are sending as many packets as possible). The result of this efforts are somewhat odd: t1+t2 manage to send each about 200k packets/s. t4 in the best case sees aroung 200k in total so half of the packets are lost. t3 is nearly unusable on console though packets are flowing through it (high numbers of soft-irqs) the route cache garbage collector is no way near to being predictable and in the default setting overwhelmed by very few packets/s (<50k packets/s) activating stateful iptables rules makes the packet rate arriving on t4 drop to around 100k packets/s, efectively losing more than 75% of the packets And this - here is my main concern - with two old P4 machines sending as many packets as they can - which means nearly everyone on the net should be capable of this. So here goes my question: Did I overlook some importand point in the config or in my test setup? Are there any alternatives for building firewall system especially on smp systems?

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• Watchguard Firebox "split" fibre optic line into 2 interfaces

  - by fRAiLtY-

  We have a requirement on our Watchguard Firebox XTM505 to be able to split our incoming external interface, in this case a fibre optic dedicated leased line, 100/100. We use the line in our office of approx 30 machines however we also re-sell to an external company who utilise it to provide wireless internet solutions to the public. The current infrastructure is as follows: Data in (Leased Line) - Juniper SRX210 managed by ISP - 1 cable out into unmanaged Netgear switch - 1 cable into our firewall and office network, 1 cable to our external providers core router managed by them. We have been informed that having the unmanaged switch in the position it is poses a security risk and that a good option would be to get our Watchguard Firewall to perform the split, by separating our office onto a trusted interface, and by "passing through" the external line to their managed router. It is alleged that the Watchguard is capable of doing this and also rate limiting the interfaces, i.e. 20mbps for the trusted interface and 80mbps for the "pass-through", however Watchguard technical support don't seem to be able to understand what we're trying to achieve. Can anyone provide any advice on whether this is possible on a Watchguard device and how or perhaps if there's a better way of achieving this, perhaps with a managed switch instead of unmanaged? Cheers

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• Fedora 19 no longer bootable

  - by Parisa

  I had fedora dual-booted with windows on my laptop for a while but with windows refresh grub was gone and my system directly booted windows. I booted fedora with my systems boot options and with this tutorial: https://fedoraproject.org/wiki/GRUB_2 I reinstalled grub2 but then had my system booted into an empty grub prompt: grub So I found the drive containing vmlinuz and initramfs (completely sure about thair location and versions) and tried to manually boot it but after the boot command it said: no suitable video mode found booting in blind mode and nothing happened. Such a tragedy... I have already tried to use live disks rescue system. Funny but troubleshooting options don't apear on my laptop while they do on my desktop pc. I cant even go to boot prompt on my lenovo idepad z400 laptop. I also tried EasyBCD so maybe I could boot it with windows but it comes up with this error: missing AutoNeoGrub().mbr Now I have removed the grub prompt (don't know why) and its really hard for me to reinstall my dearly customized fedora. If anyone knows a way to help boot it again or reinstall it keeping my files and installations I really need it. Thanks PS:I have already tried Boot-repair Disk but it asks me to enable the repo containing grub-efi on my fedora to reinstall the grub2 and fix the boot for me (how could i?).

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• Apache https is slow

  - by raucous12

  Hey, I've set apache up to use SSL with a self signed certificate. With https (KeepAlive on), I can get over 3000 requests per second. However, with https (KeepAlive off), I can only get 13 requests per second. I know there is supposed to be a bit of an overhead, but this seems abnormal. Can anyone suggest how I might go about debugging this. Here is the ab log for https: Server Software: Apache/2.2.3 Server Hostname: 127.0.0.1 Server Port: 443 SSL/TLS Protocol: TLSv1/SSLv3,DHE-RSA-AES256-SHA,4096,256 Document Path: /hello.html Document Length: 29 bytes Concurrency Level: 5 Time taken for tests: 30.49425 seconds Complete requests: 411 Failed requests: 0 Write errors: 0 Total transferred: 119601 bytes HTML transferred: 11919 bytes Requests per second: 13.68 [#/sec] (mean) Time per request: 365.565 [ms] (mean) Time per request: 73.113 [ms] (mean, across all concurrent requests) Transfer rate: 3.86 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 190 347 74.3 333 716 Processing: 0 14 24.0 1 166 Waiting: 0 11 21.6 0 165 Total: 191 361 80.8 345 716 Percentage of the requests served within a certain time (ms) 50% 345 66% 377 75% 408 80% 421 90% 468 95% 521 98% 578 99% 596 100% 716 (longest request)

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• Windows Server 2008 IIS7 - page requests randomly hang or timeout

  - by seb835

  I've just installed a fresh copy of Windows Server 2008 x64 with IIS7 and PHP (fast CGI). However, I'm noticing that after moving my web site from a similarly specified machine to this one, I'm getting issues. The issue seems to be that randomly, as I'm clicking through the web pages being served, the browser will suddenly hang saying "waiting for mysite.com...". Sometimes the page will then timeout, or finally resolve after 20 to 30 seconds, but maybe missing the CSS style sheet. Very strange, as this is the only website installed on this new server, and only myself using/testing it. Server is installed in the same data centre below the old server. Has anyone else had a similar problem? I tried increasing the max workers pool to 10 (from 1), but this has no effect. Seems to happen most frequently after 1 or 2 minutes of inactivity on the website, then trying to load/refresh a web page. Many thank for any info and help. Kind Regards, Seb

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• Ubuntu 11.04 fresh install - "Input signal out of range" or "Mode not supported..."

  - by Dennis

  I recently installed Ubuntu 11.04 using a CD .iso. Installation went fine. Upon completion I rebooted and after a second or two I got a black screen with the message "Input signal out of range". And there it sits... Read a few things about how this could be related to screen resolution, refresh rate, etc. For the heck of it I tried a different monitor. The result is the same but the message provides some clues - "Mode not supported - H:92.7kHz, V:58.3Hz" (the latter is Hz; not kHz). So my thought is that I should probably be able to use the 11.04 install disc to "Try out Ubuntu", find and edit some file that was created by the install with the correct values. Problem is, I am not too sure what I am supposed to edit. Looked at the xorg.conf file but this is so minimal at this point I am not sure it is where I want to go. By the way, the monitor is an I-Inc ix191a. Anyone have any ideas on how to get around this?

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• Questions about NGINX limit_req_zone

  - by Meteor

  I got a problem with NGINX limit_req_zone. Anyone can help? The problem is that, I want to limit user access to some specific URL, for example: /forum.php?mod=forumdisplay? /forum.php?mod=viewthread&*** But, I do want to add an exception for below URL, /forum.php?mod=image&* Below is the location section of my configuration, the problem is that, for URL started with /forum.php?mod=image&*, the limitation is still applied. Any body can help? location ~*^/forum.php?mod=image$ { root /web/www; fastcgi_pass unix:/tmp/nginx.socket; fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name; include fastcgi_params; } location ~*^/(home|forum|portal).php$ { root /web/www; limit_conn addr 5; limit_req zone=refresh burst=5 nodelay; fastcgi_pass unix:/tmp/nginx.socket; fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name; include fastcgi_params; } location ~ \.php$ { root /web/www; fastcgi_pass unix:/tmp/nginx.socket; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name; include fastcgi_params; }

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• Graphics artifacts/distortion with Win7 and nVidia

  - by Gepard

  Problem I encounter is rather hard to describe, so I provide a screenshot: http://dl.dropbox.com/u/1732760/video-distortion.png As you can see there are some horizontal stripes in random colors. These stripes appear sometimes in all windowed apps, games and on the desktop too. They tend to stay in place until I refresh window (or force it to to redraw by for example minimizing and maximizing again). They also tend to appear in the same place and shape multiple times, even if they disappear, it's very likely they will be again in the same place after a while. These artifacts do not blink or change if computer is idling. If I don't touch anything, do not use mouse, they will stay in place forever (unless some app redraws its window on its own). I first encountered this problem some weeks ago. Back then I thought it might be cooling problem, so I took out the graphics card, removed dust from the radiator and fan and put it into PC back. I also ran some stress test using Furmark (peak tempearature was ~65C) to see if the problem becomes more intense if the card gets hotter, but suprisingly no artifacts whatsoever appear during the stress test. Graphic card is Galaxy GeForce 7300 GT with DDR3 memory, was never overclocked. Drivers are the latest, from Nvidia site. OS is Windows 7 64-bit, updated. AMD64 3000+, 2GB RAM. I'm running a dual monitor setup with 2 19'' Samsung LCDs and problem is on both, so I assume it's not a monitor or cable issue.

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• Noisily rendered text in Firefox

  - by Notinlist

  It came to me in a week or so that certain pages (Facebook, StrackOverflow, some news sites) have text rendering errors in Firefox. As a workaround if I refresh the page, or simply select and deselect the buggy text, the unpleasant effect disappears. I don't have this effect in Internet Explorer or in any of my desktop applications. Windows 7 Pro 64bit (fresh) Firefox 19.0.2 (fresh) Ati Radeon HD 4600 Series (fresh drivers) Thanks for the help in advance! Update 1/2 I have only three addons: Forecastfox, Hungarian spell checking dictionary and Quick locale switcher. The latter two are installed after the effect appeared. I disabled the first individually and did not helped. But if I start my firefox with disabled addons I cannot reproduce the error. As far as I know this mode does not mean disabled plugins, which I do have (Adobe Acrobat, Citrix ICA Client, Google Earth plugin, Google update, Java Deployment Toolkit 6, MS Office 2010, MS Windows Media Player Firefox, Shockwave Flash, Silverlight, VLC Web). Update 2/2 If I disable all plugins and extensions I still have the problem. If I start Firefox with disabled addons then I cannot reproduce the problem.

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• Splitting an HTTP request into multiple byte-range requests

  - by redpola

  I have arrived at the unusual situation of having two completely independent Internet connections to my home. This has the advantage of redundancy etc but the drawback that both connections max out at about 6Mb/s. So one individual outbound http request is directed by my "intelligent gateway" (TP-LINK ER6120) out over one or the other connection for its lifetime. This works fine over complex web pages and utilises both external connects fine. However, single-http-request downloads are limited to the maximum rate of one of the two connections. So I'm thinking, surely I can setup some kind of proxy server to direct all my http requests to. For each incoming http request, the proxy server will issue multiple byte-range requests for the desired data and manage the reassembly and delivery of that data to the client's request. I can see this has some overhead, and also some edge cases where there will be blocking problems waiting for data. I also imagine webmasters of single-servers would rather I didn't hit them with 8 byte-range requests instead of one request. How can I achieve this http request deconstruct/reconstruction? Or am I just barking mad?

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• Small maximum number of connections on a Linux router

  - by Eugene

  I have a Linux box acting as a router with no iptables or other firewall and no networking applications running on it, just pure router. I've put it in a test environment that generates many TCP connections, each having unique source and destination IP, and those connections go through this router. I'm observing that number of connections successfully created rise to approximately 500 and then no more connections can be created for several minutes, then another 100 connections can be created and there is another pause, and so on. If 10 connections for each source-destination pair are created, then maximum numbers go about 10 times up, so the problem is probably with many connections from different IPs. As traffic is simply routed, it doesn't have to do with number of file descriptors, iptables connection tracking and other things often proposed to check in similar cases. The box has plenty of free RAM and CPU, both NICs are gigabit. The kernel is 2.6.32. I've already tried increasing net.core.*mem_max, net.core.netdev_max_backlog and txqueuelen on both NICs, with completely no effect. What else should I check ? Is there some rate-limit in the kernel itself ?

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• How can I prevent a DDOS attack on Amazon EC2?

  - by cwd

  One of the servers I use is hosted on the Amazon EC2 cloud. Every few months we appear to have a DDOS attack on this sever. This slows the server down incredibly. After around 30 minutes, and sometimes a reboot later, everything is back to normal. Amazon has security groups and firewall, but what else should I have in place on an EC2 server to mitigate or prevent an attack? From similar questions I've learned: Limit the rate of requests/minute (or seconds) from a particular IP address via something like IP tables (or maybe UFW?) Have enough resources to survive such an attack - or - Possibly build the web application so it is elastic / has an elastic load balancer and can quickly scale up to meet such a high demand) If using mySql, set up mySql connections so that they run sequentially so that slow queries won't bog down the system What else am I missing? I would love information about specific tools and configuration options (again, using Linux here), and/or anything that is specific to Amazon EC2. ps: Notes about monitoring for DDOS would also be welcomed - perhaps with nagios? ;)

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• Cannot make bind9 forward DNS query to subdomain unless recursive enabled

  - by PP.

  I am trying to develop my own dynamic DNS. I'm running my own custom DNS for the subdomain on port 5353. ASCII diagram: INET --->:53 Bind 9 --->:5353 node.js | V zone_files I have example.com. The node.js DNS is for dyn.example.com. In my /etc/bind/named.conf.local I have: zone "example.com" { type master; file "/etc/bind/db.com.example"; allow-transfer { zonetxfrsafe; }; }; zone "dyn.example.com" IN { # DYNAMIC type forward; forwarders { 127.0.0.1 port 5353; }; forward only; }; I've even gone so far as to add a NS in my example.com zone file: $TTL 86400 @ IN SOA ns.example.com. hostmaster.example.com. ( 2013070104 ; Serial 7200 ; Refresh 1200 ; Retry 2419200 ; Expire 86400 ) ; Negative Cache TTL ; NS ns ; inet of our nameserver ns A 1.2.3.4 ; NS record for subdomain dyn NS ns When I attempt to get a record from the subdomain server it doesn't get forwarded: dig @127.0.0.1 test.dyn.example.com However if I turn recursive on in /etc/bind/named.conf.options: options { recursion yes; } .. then I CAN see the request going to the subdomain server. But I don't want recursion yes; in my Bind configuration as it is poor security practice (and allows all-and-sundry requests that are not related to my managed zones). How does one forward (proxy) zone queries for just one zone? Or do I give up on Bind altogether and find a DNS server that can actually forward specific queries?

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• What are the advantages of registered memory?

  - by odd parity

  I'm browsing for a few low-end servers for a startup and I'm a bit confused about the different memory types. The advantage of ECC is clear - single-bit error correction. When it comes to registered memory it seems more vague, especially in systems that support both registered and unbuffered memory. A Google search mostly finds copies of the Wikipedia article, which states that registered memory chips "...place less electrical load on the memory controller and allow single systems to remain stable with more memory modules than they would have otherwise". However I can't find any quantification of this. What I'm wondering about is: Is registered memory an improvement over unbuffered when it comes to soft error rate, or is it purely about the maximum number of modules supported? If yes, at what point (amount of modules or GB of memory) do these improvements start to become noticeable? For a specific example, the HP ProLiant DL 120 G6 server manual states that maximum supported memory configuration is 16 GB unbuffered (4x4GB) or 12 GB registered (6x2GB). In this case I'd rather have the extra 4GB of memory if the reliability difference is negligible.

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• AMD processors witn graphics card bundled [closed]

  - by shybovycha

  Sorry for posting this question here - just don't know to which StackExchange website i should be writing. I've heard AMD created processors with video card bundled. So now these processors should work as fast as just usual processors with discrete video card but AMD's ones should use less power and spread less warm. Some googling around gave me the result like "AMD processors of A-series". They were mentioned to be build using that technology i described above. But on the other hand, we have a small rate of publishing and not-very-good quality of AMD drivers. I am a game-developer and web-developer so i need a powerful processor and graphics card and a lot of RAM on board (to make it possible to create a sample Grails application, for example or to create some 3D models in Maya/Cinema4D, for instance). Still i want my battery to be a long-living one, so power usage is a bit critical for me. So, my questions are: are there any processor building technology like i've described and which series they are (if they exist)? which processor shall fit the laptop the best: AMD one or i5/i7 on with nVidia graphics card for the purposes mentioned above?

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