Sysadmin: How to see the name of PHP script that sent that e-mail

phplogo SPAM e-mail is the common problem these days and in most cases the cause of this problem is the lack of security on the hosted web sites. Various badly designed PHP scripts expose the hosting server MTA to be used as SPAM e-mails source. First and foremost step in resolving this problem would be to determine the originating PHP script that was used to send e-mails.
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OSX: PPTP VPN networking problem solved with custom MTU

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I had an interesting complain the other day – customer experienced connectivity problems trying to access some web sites while on PPTP VPN connection. The VPN server was running on Linux and also under our control so troubleshooting the situation was pretty easy. All MS Windows based clients didn’t have this problem, only OSX based clients.
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Sysadmin: How to install latest ffmpeg on Centos

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I had a request to install latest ffmpeg on one of our Cnetos 5 servers the other day. Since I’m trying to stick the the proper package management I’ve had to look for the most recent ffmpeg RPM package on the pkgs.org site. As in most cases the search pointed me towards atrpms.net repository. Pkgs.org contains pretty detailed instruction on how to add the repository that contains the package you require but unfortunately it was not all that straightforward with atrpms.net
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Sysadmin: “[warn-phpd] mmap cache can’t open file … ” mystery solved


Yesterday I was asked by one of our old customers to help solving very interesting problem – he put some php files outside of apache DocumentRoot on his server and the apache could not access the files, producing very interesting lines into apache default error_log

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Sysadmin: How to make use of apache web server mod_expires to improve performance

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Most of modern Linux distributions contain Apache 2.x web server with the set of standard modules. One of these modules is mod_expires that allows to configure content expiration in local browser cache or caching proxies. Proper configuration for it can significantly improve overall server performance and reduce bandwidth consumption.
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Sysadmin: How to force fsck on reboot on single filesystem on Linux

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Recently I’ve faced a problem with some server where /usr filesystem ot an error and was switched to read-only. Otherwise server was fine and I wanted to force fsck just on this filesystem, avoiding the rest ( 500gb /home filesystem would keep server down for a loong time which is completely opposite of my goal)
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How to use BFD tool to block WordPress brute force attacks

I have written about the excellent and lightweight (unlike fail2ban which is more popular but too resource consuming and 3rd party tools dependent) tool BFD earlier. This tool is actually the set of bash scripts that looks for known pattern in the logs and executes actions against offending IPs based on the configuration. Little is known that it’s also modular and allows to extend it’s behavior by writing custom rules to assist with more uncommon situations.

I’ve also written about widespread WordPress brute force attacks that targets wp-logon.php script. The solution I’ve offered there takes care of single WordPress site. It’s getting more difficult to mitigate the attack in case you have multiple servers with multiple WordPress sites. So I decided to come up with more general approach.

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Sysadmin: How to delete specific messages from postfix queue

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In case your server mailqueue is full of messages you want to delete, most of google found instructions are not correct – there is no mailq for postfix anymore.
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PHP Catchable fatal error: Object of class Savant2_Error could not be converted to string

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This was the tale of my last couple of days. One of our long time customers was moving a bunch of web sites from various web hosting providers to her dedicated server.
As usual there was all kinds of kinks and problems during her attempts to reconfigure her web sites. Some of her sites are using Savant template system and was showing unusual behavior – request to the front page was returning status 500 – server error and while content was displaying the design of the content was altered. Unable to figure out the problem she asked for help.
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Centos: How to run multiple mysql instances on a single server

centos_iconmysql There are plenty instruction on how to run multiple mysql instances on a single server on various blogs. Most of them are based on the original mysql rpm package produced by Oracle (nowdays). In my opinion this could be unnecessary overhead when you have OS provided mysql server package and all you need to configure another instance is to slightly modify bundled configuration and init.d script.
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