Archive for the ‘Linux’ Category

17
Jul

Getting Apache Module List

As day by day you lost track of your Apache configurations and Apache modules. Here is quick shell/bash command to check which modules are loaded and compiled with your current Apache version.

httpd -l

Output will be something like this:

Compiled in modules:
core.c
mod_authn_file.c
mod_authn_default.c
mod_authz_host.c
mod_authz_groupfile.c
mod_authz_user.c
mod_authz_default.c
mod_auth_basic.c
mod_include.c
mod_filter.c
mod_deflate.c
mod_log_config.c
mod_logio.c
mod_env.c
mod_expires.c
mod_headers.c
mod_unique_id.c
mod_setenvif.c
mod_proxy.c
mod_proxy_connect.c
mod_proxy_ftp.c
mod_proxy_http.c
mod_proxy_ajp.c
mod_proxy_balancer.c
mod_ssl.c
prefork.c
http_core.c
mod_mime.c
mod_status.c
mod_autoindex.c
mod_asis.c
mod_suexec.c
mod_cgi.c
mod_negotiation.c
mod_dir.c
mod_actions.c
mod_speling.c
mod_userdir.c
mod_alias.c
mod_rewrite.c
mod_so.c

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4
Jul

How to check DDOS Attack on Server

A quick and useful command for checking if a server is under DDOS:

netstat -anp |grep 'tcp\|udp' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n

This will list the IPs taking the most amounts of connections to a server.

To check active connections that are open to your server, if this number is more then 800 then you might be having an attack

netstat -n | grep :80 |wc -l

To check against SYN attacks, this number should not be more then 100.

netstat -n | grep :80 | grep SYN |wc -l

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3
Jul

Basic Bandwidth & Network Usage Analysis

As I was doing my co-worker’s system administrative tasks last month, I always was asked this question why one of client server is having slow speed issues. Well who knows until you check try to solve the problem :)

Few things you can always do to check for bandwidth and network analysis.

Install IPTraf – IPTraf is a console-based network statistics utility for Linux. It gathers a variety of figures such as TCP connection packet and byte counts, interface statistics and activity indicators, TCP/UDP traffic breakdowns, and LAN station packet and byte counts.

yum install iptraf -y

Install vnStat – vnStat is a network traffic monitor for Linux that keeps a log of daily network traffic for the selected interface. vnStat isnt a packet sniffer. The traffic information is analyzed from the /proc -filesystem, so vnStat can be used without root permissions.

cd /usr/local/src
wget http://humdi.net/vnstat/vnstat-1.6.tar.gz
tar -zxvf vnstat-1.6.tar.gz
cd vnstat-1.6
make && make install
vnstat -u -i eth0
vnstat --help

Check Apache connection and always check for DDOS attacks.

If your server is WHM / CPanel configured always check bandwidth usage from WHM / CPanel and do the comparing.

Above will give few ideas whats happening on server, and actually you can come up with solution based on these few basic in house tasks.

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