Amit's Blog

route add -host x.x.x.x dev eth0

route add default dev eth0 gw x.x.x.x```

#!/bin/bash

PORT="non standard port number"

if [ -z "$1" ]; then

echo "Usage: $0 hostname"

else

ssh -p $PORT $1

fi```

Example Rules domain.com permanently moved to domain2.com RewriteCond %{HTTP_HOST} ^www.domain.com$ [NC] RewriteRule ^(.*)$ http://www.domain2.com/$1 [R=301,L] domain.com/page.html moved to domain.com/new_page.html temporarily RewriteRule ^page.html$ new_page.html [R,NC,L] **Nice looking URLs (no

Add these two line to your httpd.conf immediately after RewriteEngine On. `RewriteLog “/var/log/httpd/rewrite_log”``` RewriteLogLevel 9

Rename multiple files: for i in *.dns; do mv "$i" "basename $i .dns.zone"; done or for i in *.JPG; do mv "$i" "${i/.JPG}".jpg; done

Adding a machine to samba : useradd -s /bin/false -d /dev/null machine_name$

Creating a Tarball with compression: tar -czvf tarball.tar.gz folder/ Extracting a Tarball: tar -zxvf tarball.tar.gz Viewing the contents of a tarball tar -tvf tarball.tar.gz Extracting a single file from tarball tar -zxvf  tarball.tar.gz folder/filename or tar --extract --file=tarball.tar.gz

#!/bin/bash

SKIPDB="mysql test"

BACKUP_DIR="/backup/dir"

DBS="$(mysql -Bse 'show databases')"

for db in $DBS;do

echo "Backing up Database:$db"

mysqldump $db | /bin/gzip -9 > ${BACKUP_DIR}/${db}.gz

echo "Backup complete for DB:$db"

done```

Regular Expression Syntax ^ Start of string $ End of string . Any single character (a|b) a or b (…) Group section [abc] Item in range (a or b or c) [^abc] Not in range (not a or b or c) a? Zero or one of a a* Zero or more of a

Apache Rewrites can be handy in various scenarios. In order to use apache  rewrite you have to have the mod_rewrite enabled. Syntax:  RewriteRule [Optional Flags] RewriteEngine On RewriteRule ^(test)/([0-9A-Za-z-]+)$   test.php?id=$2  [L] This will redirect url/test/53xml to url/test.

Get the Latest Source from svn: Download Ruby Version 1.8.7 RubyForge [http://ftp.ruby-lang.org/pub/ruby/ruby-1.8.7-p352.tar.gz] wget http://ftp.ruby-lang.org/pub/ruby/ruby-1.8.7-p357.tar.gz

Checkout Redmine from svn svn co http://redmine.rubyforge.org/svn/branches/1.3-stable

If you need to login to a server and frequently switch to a path, you might want to create a shell script to switch . eg. #!/bin/bash

cd /path/to/where/you/want/to/go``` Now the trick is you need to run the shell script as : . ./script.sh```

#!/bin/bash

if [ -z "$1" ];then

echo "Usage:$0 "

else

abuse=`echo $1| cut -f2 -d.`

log_seq=0

if [ "$log_seq" -le 1 ];then

log_file=/var/log/maillog

else

log_file=/var/log/maillog/$log_seq

fi

cat $log_file | grep $abuse | grep -w relay | awk '{print

It is possible to grant ftp access to files outside the home directory of the user. #vi /etc/vsftpd/vsftpd.conf **Uncomment or add the following : ** chroot_local_user=YES Now create a directory to mount the folder to users home directory which you want to grant access to: mkdir

Zabbix Server Create user and groups for zabbix groupadd -g 130 zabbix

useradd -u 130 -g zabbix -c 'Zabbix monitoring' zabbix``` **Install Dependencies:** `yum install zlib-devel mysql-devel glibc-devel curl-devel gcc automake mysql libidn-devel openssl-devel net-snmp-devel rpm-devel OpenIPMI-devel` For Centos 5: rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/

Download the latest source from lighttpd.net $wget -O http://download.lighttpd.net/lighttpd/releases-1.4.x/lighttpd-1.4.29.tar.gz /usr/src/lighttpd.tar.gz

$cd /usr/src

$tar -zxvf lighttpd.tar.gz

$cd lighttpd``` **Now Configure lighttpd:** $ ./configure --host=i686-redhat-linux-gnu --build=i686-redhat-linux-gnu --target=i386-redhat-linux
--program-prefix= --prefix=/usr

Php Tweaks, settings and tricks Php Set display Error for a specific page: To display errors for a specific page, set this on the top of the php page: ini_set(‘display_errors’, 1); ini_set(‘log_errors’, 1); ini_set(‘error_log’, dirname(FILE) . ‘/error_log.txt’); error_reporting(

Zabbix Monitor Postfix queue: UserParameter=postfix.queue,postqueue -p | find /var/spool/postfix/{deferred,active,maildrop}/ -type f | wc -l [Note: This will have permission issues ] The following one is even better: UserParameter=postfix.queue,mailq | grep -v "Mail queue is empty" | grep -c '[1] ' Check if the

Create a directory to share mkdir /var/share vi /etc/exports /var/share 192.168.100.100(ro,no_root_squash,sync) Now to apply changes you can : exportfs -a To verify : exportfs For the first time , you want to restart the services : service nfs start service portmap start Mounting

#!/bin/bash

if [ $# -ne 1 ];then

echo "0";

else

/bin/ls -l $1 | awk '{print $5}'

fi```

Doing an Arithmetic : i=$((  i * 5 )) Single Quotes: Ignoring special Characters : echo ‘*’ [ anything inside single quotes is ignored ] Double Quotes: Same as single quotes but not restrictive. The BackSlash: Equivalent to single quotes around a single character. Backslash quotes the single character $(…) Construct : $(command) is same as command and is

Period (.) = Match any single character **Caret (^) **= Match the begining of the line Dollar ($) = Match the end of the line **[…] **= Match a choice of characters eg. [abcABC] Asterisk(*) = Matching zero or more characters {min,max} = Matching Precise number of characters: {…} Saving Matched Characters : ^\(.\)\1 : Matches first character on the line , and

Getting Information from a file : ffmpeg -i filename.ext Turn images to a video sequence: ffmpeg -f image2 -i image%d.jpg video.mpg ( converts images labeled 1,2,3 into a video) Turn video to images: ffmpeg -i video.mpg image%d.jpg Reduce the volume of an audio