Amit's Blog (Page 6)

Call a url from bash script

curl "http://www.amitnepal.com?inquiry.php?id=2&question=test"

Useful Find Commands

Find Files by name: find /path -name filename find /tmp /home . $HOME -name Find Files Larger than 1Gb find /path -type f -size +1048576 Find with wildcard: find / -name file\*name Find and process find / -type f -mtime -3 | xargs tar -rf archieve.tar [should not use -c option here,

Bash Script to check if a host is alive

Script to check if a host is alive: #!/bin/bash ping -c 2 www.amitnepal.com > /dev/null if [ $? -eq 0 ]; then echo "Alive"; </br&

Adding a Start/Stop Script to chkconfig

In order to add a script to be manageable by chkconfig, you should create the /etc/init.d/example script that has the ability to start and stop script. Now put the following two comments around the header of the script # chkconfig: 345 80 20 </br&

Export Putty Sessions

regedit /e "%userprofile%\desktop\putty-registry.reg" HKEY_CURRENT_USER\Software\Simontatham

Sample mysql queries

Delete Rows based on output from a query : DELETE FROM Table1 WHERE EXISTS(SELECT 1 FROM Table2 WHERE Table2.Group = Table1.Group) or delete from Table1 where id in (select id from table1 inner join table2 on Table1.

Handling arguments in bash

#!/bin/bash echo Total Number of Arguments Passed: $# i=1; for var in "$@" do echo "Argument $i

Handling parameters in Bash

Short Mode Only : #!/bin/bash while getopts :a:b:c opt #define options here : at the front supress error for unknown options do case $opt in&

Check Load average

uptime | awk ‘{print $10}’ | sed ‘s/,//g’

Nice and Renice

Nice command can be used to start a process with low/high priority: nice -n command value = -20 for highest priority and 20 for lowest priority To reset the priority of a running process, find the pid of the process and run: renice renice +1 102 -u daemon root -p

Shell Script to Backup and Rotate Mysql Database

#!/bin/bash #Author : Amit K Nepal #Last Modified : Nov 01 2011 BACKUP_DIR=/db_backups DB_NAME=dbname TSTAMP=`date

Writing Iptables rules by hand

*nat :PREROUTING ACCEPT [92:7226] :POSTROUTING ACCEPT [62:3916] :OUTPUT ACCEPT [62:3916] COMMIT *filter :INPUT DROP [0:0] :FORWARD DROP [0:0] :OUTPUT ACCEPT [0:0] COMMIT

Sample Kickstart file for Redhat / Centos

platform=x86, AMD64, or Intel EM64T # System authorization information auth --useshadow --enablemd5 # System bootloader configuration bootloader --location=mbr --password=grub # Clear the Master Boot Record zerombr # Partition clearing information clearpart --all --initlabel # Use text mode install text # Firewall configuration firewall --enabled --http --ftp --ssh --telnet --smtp # Run the Setup Agent

write to a file using php

$myFile = "testFile.txt"; $fh = fopen($myFile, 'a') or die("can't open file"); $stringData = "New Stuff 1\n"; fwrite($fh, $stringData); $stringData = "New Stuff 2\n"; fwrite($fh, $stringData); fclose($fh);

shell script to monitor port and notify by email

!/bin/bash ADMIN_EMAIL="email" PID=$$ POLL_INTERVAL=2 trap traphup HUP sleep 1 i=1 laststate="STARTUP" notify() { #echo "Service State Changed to $1" | mail -s "Service Status Notification" $ADMIN_EMAIL echo "Admin has been notified $1" } while [ $i

One liner to change ssh port

You can pass port as parameter too. (/usr/sbin/sshd -t : to check for syntax errors) sed -ie 's/Port.*[0-9]$/Port '2222'/gI' /etc/ssh/sshd_config

Shell script to run command on multiple servers

This is great script to run commands on multiple servers at once, especially if you have setup password less connections. !/bin/bash servers="srv1.example.com srv2.example.com srv3.example.com" SSH_PORT=22 cmd=$1 if [ "$cmd" == "" ]; then echo "Usage sh

C,C++ compiler cannot create executables

C++ compiler cannot create executables : Install gcc, gcc-c++

System Monitoring , disk,cpu and memory

Displays top cpu eaters ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10 Top Memory Eaters: ps -auxf | sort -nr -k 4 | head -10 Load Average : uptime | awk '{print $10}' | sed 's/,//g' Total No. of Cpus [cores]: cat /proc/cpuinfo | grep processor

connect to 127.0.0.1[127.0.0.1]:10024: Connection refused.

This is an error with amavisd . Check the proper hostname, that could be guilty.. vi /etc/amavisd.conf and check for hostname Or, vi /etc/postfix/main.cf find content_filter and comment that out ( Temp solution ) Amavis dead but subsys locked : rm /var/amavis/amavisd.pid rm /var/amavis/

Using remote mail server with postfix.

Setting up Postfix to use a remote mailserver Edit /etc/postfix/main.cf and add the following > Set this to your email provider’s smtp server. relayhost = yourisp.smtp.servername:25 #or your smtp port if different smtpd_sasl_auth_enable = yes smtpd_sasl_path = smtpd smtp_sasl_password_

Common Ports

Rsync : 873

Iptables tutorial and examples

Delete existing rules: iptables -F or iptables --flush Set Default Chain Policies: iptables -P INPUT DROP iptables -P FORWARD DROP iptables -P OUTPUT DROP Block an IP Address: iptables -A INPUT -s a.b.c.d -j DROP iptables -A input -i eth0 -p tcp -s <ip_addr>

Awk Tutorials and examples

Using Awk to sum the list of output: ps aux | awk '{sum +=$4}; END {print sum}' Print Line that match a pattern: awk ‘/string1/ > /string2/’ filename Print specific fields : awk ‘{print $1,$3,$5,$NF;}’ /etc/passwd [ $NF means the last field ] Initialization and Finalization: BEGIN {actions}

Using TcpDump to monitor network activity

Note : Default packet size sniffed is 96 bytes, you can override that with -s , you can use –s 0 for complete size capture. Example usage : tcpdump -w capture.pcap -i eth0 tcp port 22 To capture or view for multiple ports : tcpdump -w capture.pcap -i eth0 tcp port 22