Posts Tagged ‘openvz’

How to install php mbstring support (add php mbstring module) on CentOS 5.5

Tuesday, August 2nd, 2011

I needed to install support for mbstring, as it was required by a client hosted on one of the servers running on CentOS 5.5.

Installation is quite straight forward as php-mbstring rpm package is available, here is how to install mbstring:

[root@centos [~]#yum install php-mbstring

Further on a restart of Apache or Litespeed and the mbstring support is loaded in php.
On some OpenVZ CentOS virtual servers enabling the php-mbstring might require also a complete php recompile if php is not build with the –enable-mbstring

If thus the mbstring has to be enabled on an OpenVZ server with php precompile, this can be easily done with cpeeasyapache , like so

server: ~# cd /home/cpeasyapache/src/php-5.2.9
server: php-5.2.9# cat config.nice |head -n $(($(cat config.nice |wc -l) - 1)) >>;
server: php-5.2.9# echo "'--enable-mbstring' \" >>; echo '"$@"' >>
server: php-5.2.9# mv config.nice config.nice.orig; mv config.nice

After that follow the normal way with make, make install and make install modules , e.g.:

server: php-5.2.9# make && make install && make install modules

Next the php-mbstring is enabled enjoy 😉

How to find and kill Abusers on OpenVZ Linux hosted Virtual Machines (Few bash scripts to protect OpenVZ CentOS server from script kiddies and easify the daily admin job)

Friday, July 22nd, 2011

OpenVZ Logo - Anti Denial Of Service shell scripts

These days, I’m managing a number of OpenVZ Virtual Machine host servers. Therefore constantly I’m facing a lot of problems with users who run shit scripts inside their Linux Virtual Machines.

Commonly user Virtual Servers are used as a launchpad to attack hosts do illegal hacking activities or simply DDoS a host..
The virtual machines users (which by the way run on top of the CentOS OpenVZ Linux) are used to launch a Denial service scripts like, trinoo, shaft, tfn etc.

As a consequence of their malicious activities, oftenly the Data Centers which colocates the servers are either null routing our server IPs until we suspend the Abusive users, or the servers go simply down because of a server overload or a kernel bug hit as a result of the heavy TCP/IP network traffic or CPU/mem overhead.

Therefore to mitigate this abusive attacks, I’ve written few bash shell scripts which, saves us a lot of manual check ups and prevents in most cases abusers to run the common DoS and “hacking” script shits which are now in the wild.

The first script I’ve written is , what the script does is to automatically look up for a number of listed processes and kills them while logging in /var/log/abusers.log about the abusive VM user procs names killed.

I’ve set this script to run 4 times an hour and it currently saves us a lot of nerves and useless ticket communication with Data Centers (DCs), not to mention that reboot requests (about hanged up servers) has reduced significantly.
Therefore though the scripts simplicity it in general makes the servers run a way more stable than before.

Here is OpenVZ kill/suspend Abusers procs script ready for download

Another script which later on, I’ve written is doing something similar and still different, it does scan the server hard disk using locate and find commands and tries to identify users which has script kiddies programs in their Virtual machines and therefore are most probably crackers.
The scripts looks up for abusive network scanners, DoS scripts, metasploit framework, ircds etc.

After it registers through scanning the server hdd, it lists only files which are preliminary set in the script to be dangerous, and therefore there execution inside the user VM should not be. then logs in a files it’s activity as well as the OpenVZ virtual machines user IDs who owns hack related files. Right after it uses nail mailing command to send email to a specified admin email and reports the possible abusers whose VM accounts might need to either be deleted or suspended.

search_for_abusers can be download here

Honestly I truly liked my script as it became quite nice and I coded it quite quickly.
I’m intending now to put the Search for abusers script on a cronjob on the servers to check periodically and report the IDs of OpenVZ VM Users which are trying illegal activities on the servers.

I guess now our beloved Virtual Machine user script kiddies are in a real trouble ;P

Installing HTOP on CentOS 5.5 OpenVZ Linux server from source

Friday, July 22nd, 2011

Htop Cool picture logo / htop on CentOS OpenVZ

Lately, I’m basicly using htop‘s nice colourful advanced Linux top command frontend in almost every server I manage, therefore I’ve almost abondoned top usage these days and in that reason I wanted to have htop installed on few of the OpenVZ CentOS 5.5 Linux servers at work.

I looked online but unfortunately I couldn’t find any rpm pre-built binary packages. The source rpm package I tried to build from dag wieers repository failed as well, so finally I went further and decided to install htop from source

Here is how I did it:

1. Install gcc and glibc-devel prerequired rpm packages

[root@centos ~]# yum install gcc glibc-devel

2. Download htop and compile from source

[root@centos src]# cd /usr/local/src
[root@centos src]# wget ""
Connecting to||:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 418767 (409K) [application/x-gzip]
Saving to: "download"

100%[======================================>] 418,767 417K/s in 1.0s
2011-07-22 13:30:28 (417 KB/s) – “download” saved [418767/418767]

[root@centos src]# mv download htop.tar.gz
[root@centos src]# tar -zxf htop.tar.gz
[root@centos src]# cd htop-0.9
[root@centos htop-0.9]# ./configure && make && make install

make install should install htop to /usr/local/bin/htop

That’s all folks! , now my OpenVZ CentOS server is equipped with the nifty htop tool 😉