amit - Amit's Blog (Page 2)

ZIP tips and tricks in Linux

View List of files inside a zip file: unzip -l filename.zip (list files ) Extract Single File from a zip file: unzip -j "archive.zip" "archive/filename.zip" -d .

qmail

Root Alias with Qmail

In order to create root alias , you have to edit the .qmail-root file on qmail server vi /var/qmail/alias/.qmail-root Now add the email address that you want to alias to and add & at the begining &sendto@domain.com [&sendto@domain.com]

Chrooting Users with SFTP

Prerequisite : OpenSSH 4.9p1 or newer is required, you can verify with the following command : Note : User can be added with /bin/false or /bin/bash if you want to allow shell access , for shell access refer to the bottom section as well. rpm -qa | grep -i openssh Match User

Iptables initial Configuration

Iptables Configuration*filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] Block all other hackers and hacking attempts or exclusive block here -A INPUT –s x.x.x.x –j DROP Reject packets from RFC1918 class networks on your wan interface, which would mean spoofed Assumption

Log Messages with specific prefix to a separate file

With rsyslog you can log messages with specific prefix to a separate file. For example, if you wanted to put iptables log into a separate log file, with the syslog you have to live with log combined with kernel logs. In order to put the iptables log to a separate

Download RPM Packages with yum

Sometimes, it is desirable to download packages from yum repo.Here is how you can do that. Yum download only plugin is required. yum install yum-downloadonly After installing that plugin , you can download the packages as : yum install --downloadonly --downloaddir=/usr/local/src/

Email Server Utilities

To check for email report including SPF, Domain Keys , send a blank email to : check-auth@verifier.port25.com and wait for the reply with all the report.

Block Chinese Spam

Charsets from asia: /^Content-type:.charset\s=[\s"] (big5|euc-kr|gb2312|ks_c_5601-1987|ISO-2022-JP)/ REJECT /^Subject:.[Big5]./ REJECT /^Subject: =?iso-8859-1./ REJECT

PHP

Php Display only number of characters from string

This is an example to display only 13 characters from a string: $string = (strlen($string) > 13) ? substr($string,0,10).'...' : $string;

PHP

Execute Windows Batch File from php

If you ever needed to execute a batch file from php, you run it as : system ("cmd /c C:/path-to/file.bat");

windows scripting

Terminating a windows process with a Batch File

You might come acrosss a situation where you would want to terminate a process with a batch file. Below is a sample script to do so. @ echo off REM Sample Script to look for a process and kill another process if earlier process is not running REM Error level 1

mysql replication

Running a query without affecting slave

Some times, you might want to run a query without slave updating with that query. In that case, you would have to avoid writing the query to the binary log , to do that, you would have to turn off binary logging for the current session. Login to the mysql and

turn off ethernet auto negotiation

Turn off ethernet negotiation Linux

Sometimes you might come across a situation where you need to manually set the ethernet speed and turn off the auto negotiation. In the below example, we set the ethernet speed to 1GBPS and turn off auto negotiation : ethtool -s eth0 speed 1000 ethtool -s eth0 autoneg off

Open SSL commands

Here are some very useful open-ssl commands : To check openssl version : openssl version -a **Check information in a certificate : ** openssl x509 -text -in api_cert_chain.crt List of all available ciphers: openssl ciphers -v List available TLSv1 ciphers : openssl ciphers -v -tls1 List only ciphers with High encryption: openssl

MySQL root grant permission denied

There are times, when you may come across this situation, when you are not able to grant permission to a new user, even when you are root. This seems to happen , either when you have deleted root account or when you have restored a database from previous version of database

Printing Content past a specific string From a file

t“tac” could be a great tool when you need to read something from backwards. You can read a file from backward, and find the first occurrence of a string of your interest and print everything after it, that way you can get the content past a specific string from

yum update error: Error: pkgKey doesn't exist in repo base

You can solve this problem by cleaning your yum metadata and cache. yum clean all yum clean metadata

vsftpd

Enabling Passive FTP Connections through IPTABLES

Sometimes when you have an FTP Server running behind IPTABLES, some clients cannot connect to the FTP. This is generally because of the inability of the firewall to track the ftp connections. You can load iptables module IP_CONTRACK_FTP to enable tracking ftp connections. First of all make sure

Bash Get Extension from filename

fileName=’/path/to/testfile.ext' ext=${fileName/*./} echo “Extension: $ext”

Configure Postfix as a backup MX

In order to configure postfix as a backup mx, you need to make some changes to the configuration file : Add the following line to the main.cf file: vi /etc/postfix/main.cf Add permit_mx_backup to the smtpd_restrictions : smtpd_recipient_restrictions = current_restrictions, permit_mx_backup permit_

Remote Desktop Login Success / Failure Email Notification

Section and You can reference the IP and Username as below :

Accessing a URL protected by htpasswd (Basic Auth) with php

It is possible to access a URL protected by htpasswd with Basic Authentication through php scripts. Here is an example : array( 'method' => 'POST', 'header' => "Content-Type: text/xml\r\n". "Authorization: Basic ".base64_encode("$https_user:$https_password&

Installing Gluster FileSystem in Centos

Gluster file system is a highly scalable file system. Here i present a small tutorial on how to install Gluster file system. yum install bison flex python-ctypes fuse fuse-libs fuse-devel wget http://download.gluster.org/pub/gluster/glusterfs/LATEST/glusterfs-3.3.0.tar.gz tar -zxvf glusterfs-3.3.0.tar.

voip

Kamailio Errors and Solutions

FIFO stat failed: Bad address I came across this error when trying to run fresh install of kamailio 3.3.3 via the init script. However, when I ran kamailio , it was running fine. So I thought there was something to do with the init script. After going through the

Kamailio Log Management

Separate Log File for Kamailio In order to create a separate log file for kamailio, you would need to edit two files. First , set the log_facility directive : vi kamailio.cfg log_facility=LOG_LOCAL0 Edit the syslog configuration file depending upon your daemon vi /etc/rsyslog.conf or vi