Amit's Blog (Page 7)

Adding colors to shell scripts

Define the colors : ESC_SEQ=”\x1b[” COL_RESET=$ESC_SEQ”39;49;00m” COL_RED=$ESC_SEQ”31;01m” COL_GREEN=$ESC_SEQ”32;01m” COL_YELLOW=$ESC_SEQ”33;01m” COL_BLUE=$ESC_SEQ”34;01m” COL_MAGENTA=$ESC_SEQ”35;01m” COL_CYAN=$ESC_SEQ”36;01m” echo

Bash Tutorials and snippets

Reading user input with timeout: > read -t eg. > echo -n “Are you Sure ? ” if read -t 5 response; then echo ” Timed out, you didn’t make a selection” else echo “Ok proceeding” fi ** Read with prompt :** read -p “Enter Name: ” name Get File Name from full path: filename=

Compile error : undefined reference to pthread_once and dlopen

LIBS=”-lpthread -ldl”

Shell Script to Calculate Memory Usage by A Process

The following script will calculate the Total Memory Usage by A process in Megabytes and the number of threads. You have to supply the string that will identify the process in ps aux output. sample usage calc_memory.sh apache > !/bin/bash STRING=$1 if [ -z "$STRING"

Bash Add numbers output in a shell

Pipe any output to : > awk ‘{total = total +$1}END{print total}’

Php Session Timeout

Creating an activity timeout using php: > function check_session() { if (isset($_SESSION[‘last_active’]) && (time() – $_SESSION[‘last_active’] > 300)) { // last request was more than 30 minates ago /* destroyPortalSession(); redirect(‘/’); session_destroy(); // destroy session data in storage session_unset(); // unset $_SESSION variable for the runtime */ header(“Location:

Additional Yum Repositories

Installing Additional Yum Repositories Installing Centos Testing Repo : > rpm –import http://dev.centos.org/centos/RPM-GPG-KEY-CentOS-testing wget -O /etc/yum.repos.d/CentOS-Testing.repo http://dev.centos.org/centos/5/CentOS-Testing.repo Installing Rpm Forge Repo: Centos 6: i686 : > http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el6.

Mysql Tips and Tricks

View Mysql Process list with full query : show full processlist \G Disable Binary Logging SET sql_log_bin = 0;

Css Cheat Sheet

CSS 2 : Image List : > ul { list-style-image: url(‘img.ext’); } Cross Browser Solution ( Clear First ) : > ul { list-style-type: none; padding: 0px; margin: 0px; } li { background-image: url(sqpurple.gif); background-repeat: no-repeat; background-position: 0px 5px; padding-left: 14px; } Set Static Content ( Doesnot moved when scrolled ) > p.pos_fixed { position:fixed; top:30px;

Finding and optimizing fragmented tables in mysql

With increasing data, mysql tables can get defragmented and it is a good idea to optimize tables every once in a while.Getting the list of all tables that need optimization :> mysql -p -e “select concat(TABLE_SCHEMA,’.’,TABLE_NAME),Data_free from information_schema.TABLES where TABLE_SCHEMA

Reset Postfix Admin password

Follow the following steps to reset the postfixadmin password: 1. Get the Encrypted Version of the string that you want to set as password : > dovecot -s MD5-CRYPT -p | sed ‘s/{MD5-CRYPT}//’ 2. Copy the output 3. Login to Mysql database 4. Use database Vmail or whatever in your case.

Shared Libraries

In Linux, the shared libraries are usually search at /usr/lib, if you need to force it to search in a new directory then you have to create a file with .conf extension inside /etc/ld.so.conf.d and add the path to that file example : > vi /etc/

Grep Tutorials

Search for a pattern in current directory: grep -w : match exact word grep -i : ignore case grep -v : Dont mach this grep -l : Only show filename that matches the pattern grep -n : Show the line number where the match is found. eg: grep ‘[A-Z]’ files : Lines containing a caps grep

Find Dell service tag

Find Service tag for dell machines dmidecode | grep –color -i serial or dmidecode -t 1

cut awk

print nth field using awk / cut echo 'This is a test' | awk '{print substr($0, index($0,$3))}' awk '{print substr($0, index($0,$3))}' <<< 'This is a test' echo 'This is a test' | cut -d '

Wget Tutorials

Wget Tips & Tricks Download to a different folder : > wget -O /etc/yum.repos.d/CentOS-Testing.repo http://dev.centos.org/centos/5/CentOS-Testing.repo Download File with Authentication: > wget –http-user=Username –http-password=password ‘url_to_download’ Using Curl : > curl –user $USERNAME ‘url’ Download with Rate Limited

Delete Master Boot Record (MBR)

dd if=/dev/zero of=/dev/sdc bs=512 count=1

Compression Utilities

Tar : Create a tar ball tar -cvf tarfile.tar Extract from Tar tar -zxvf tarfile.tar Create Tar ball with compression tar -czvf tarfile.tar or tar -cjvf tarfile.tar Display Files inside a tarball: tar -tvf tarball.tar Delete a single file from inside the tarball tar –delete -f

Nagios Installation on Centos

** Install Nagios on Centos** Download the latest version of nagios core and plugins from : http://www.nagios.org/download Install Pre-requisites: > yum install httpd gc glibc glibc-common gd gd-devel php Add user and group : > useradd -m nagios groupadd nagcmd usermod -a -G nagcmd nagios usermod -a -G nagcmd

Security

Apache Security

Trace Back : Testing if Trace back is enabled : telnet localhost 80 TRACE / HTTP / 1.0 If you get any response back trace is enabled. Disabling Trace Back : vi /etc/httpd/conf/httpd.conf TraceEnable off or , use an htaccess or rewrite rule : RewriteEngine On RewriteCond %{REQUEST_METHOD} ^TRACE RewriteRule .* -

Rootkit Hunter--check if your system has been compromised

Download Rootkit Hunter Here [http://downloads.sourceforge.net/project/rkhunter/rkhunter/1.3.8/rkhunter-1.3.8.tar.gz?r=http%3A%2F%2Fsourceforge.net%2Fprojects%2Frkhunter%2F&ts=1316446867&use_mirror=voxel] Untar and cd into the directory ./installer.sh –layout default –isntall rkhunter –update Now, you

Securing Server with Iptables ( Block Except )

Securing Server with Iptables Iptables is a great firewall when configured properly but sometimes you can lock yourself out with what you didn’t mean to. When you are starting to work on your firewall, it is always a good idea to create a cron job that will stop iptables

Block Ports in IPtables

Blocking Ports in Iptables In order to block a single port you can use the following statement : > iptables -A INPUT -p <protocol – udp or tcp> –dport -j REJECT In order to block multiple ports , use the following statement : > iptables -A INPUT -p -m multiport –dports port1,

firewall

Redirect or forward ports in iptables

Redirect or Forward Ports using Iptables Port Redirection: iptables -t nat -A PREROUTING -i <interface> -p tcp --dport <port number=""> -j REDIRECT --to-port <port_number></port_number></port></interface> or iptables -t nat -I PREROUTING --src

Optimize MySQL From my-large.cnf

1. Copy the my-large.cnf which usually comes with mysql-server , usually inside the /usr/share/mysql directory Note: you might want to backup your existing my.cnf before doing this. > cp -p /usr/share/mysql/my-large.cnf /etc/my.cnf Note: All values are in seconds for time and