How to change the linux hostname?

# hostname
test.com

# hostname server.com

# hostname
server.com

# vi /etc/hostname
server.com

Now restart and see the changes.

How to change MySql root password?

For every database, you should set the root or sa passwords to something other than the default, unless you want to get hacked. For mysql, the system administrator user is called root. You will use the mysqladmin utility from a command line to set the new password.

Syntax:

# mysqladmin -u root password “new_password”

# mysqladmin -u root -h host_name password “new_password”

Example:

# mysqladmin -u root password Pa55w0rD

# mysqladmin -u root -h localhost password linuxgEEks

You need to restart the database server after this change

# /etc/init.d/mysql restart

How To Backup MySQL Database to a file?

Backing up your database is a very important system administration task, and should generally be run from a cron job at scheduled intervals. We will use the mysqldump utility included with mysql to dump the contents of the database to a text file that can be easily re-imported.

Syntax:

# mysqldump -h localhost -u root -pmypassword database_name > dumpfile_name.sql

Example:

# mysqldump -h localhost -u root -pPa55w0rD database110 > backup_file.sql

This will give you a text file containing all the commands required to re-create the database.

How To Set SSH Login Message?

To set ssh login message, its very easy and interesting.
# vi /etc/motd
write the message of your own

######### Welcome to the SSH World #########
### This is the Email Server, please exit properly ###
########################################

Save and Quit

// To check quit the ssh terminal and re-login...


######### Welcome to the SSH World #########
### This is the Email Server, please exit properly ###
########################################

Thats all, Enjoy!!!!!

nmap in details

nmap is a tool to check the status of ports in any machine

Example1 : To scan a particular system for open ports
#nmap hostname

Example2 : Scanning for a single port on a machine
#nmap –p 22 hostname
–p indicates port.

Example3 : For scanning only ports
#nmap –F hostname

-F is for fast scan and this will not do any other scanning like IP address, hostname, operating system, and uptime etc.

Example4 : Scanning only TCP ports
#nmap –sT hostname
-s is for scanning and T is for only scanning of TCP ports

Example5 : Scanning only UDP ports
#nmap –sU hostname
-U indicates UDP port scanning

Exmaple6 : Scan for ports and get the version of different services running on that machine
#nmap –sV hostname
-V indicates version of each network service running on that host

Example7 : Check which protocol is supported by the remote machine
#nmap –sO hostname

Example8 : Scan a system for operating system and uptime details
# nmap -O hostname
-O is for operating system scan along with default port scan

Example9 : Scan a network
#nmap networkID/subnetmask
For the above command you can try in this way
#nmap x.x.x.x/24

Netstat in Linux

List all ports
# netstat -a | more

List all tcp ports using netstat -at
# netstat -at

List all udp ports using netstat -au
# netstat -au

List only listening ports
# netstat -l

List only listening TCP Ports using netstat -lt
# netstat -lt

List only listening UDP Ports using netstat -lu
# netstat -lu

List only the listening UNIX Ports using netstat -lx
# netstat -lx

Show statistics for all ports
# netstat -s

Show statistics for TCP/UDP ports
# netstat -st
# netstat -su

Display PID and program names
# netstat -pt

Don’t resolve host, port and user name
# netstat -an

Print netstat information continuously
# netstat -c

Find the non supportive Address families in your system
# netstat --verbose

Display the kernel routing information
# netstat -r

Find out on which port a program is running
# netstat -ap | grep ssh

Find out which process is using a particular port
# netstat -an | grep ':80'

Show the list of network interfaces
# netstat -i

Display extended information on the interfaces
# netstat -ie

How to install SendMailAnalyser in linux, centOS?

SendmailAnalyzer can work in any platform where Sendmail and Perl could run. What you need is a modern Perl distribution 5.8.x or more is good but older version should also work.

Download sendmailanalyzer-x.x.tar.gz and perform the following opertaions

# tar -zxvf sendmailanalyzer-x.x.tar.gz
# cd sendmailanalyzer-x.x/
# perl Makefile.PL
# make && make install

Start SendmailAnalyzer daemon:

# /usr/local/sendmailanalyzer/sendmailanalyzer -f

Add httpd configuratiosn for SendmailAnalyzer

Alias /sareport /usr/local/sendmailanalyzer/www

<Directory /usr/local/sendmailanalyzer/www>
Options ExecCGI
AddHandler cgi-script .cgi
DirectoryIndex sa_report.cgi
Order deny,allow
Deny from all
Allow from 127.0.0.1
Allow from ::1
# Allow from .example.com
</Directory>

Test:

http://server_ip_address/sareport

Additional tasks to be added in crontab

# SendmailAnalyzer log reporting daily cache
0 1 * * * /usr/local/sendmailanalyzer/sa_cache > /dev/null 2>&1
# On huge MTA you may want to have five minutes caching
#*/5 * * * * /usr/local/sendmailanalyzer/sa_cache -a > /dev/null 2>&1

Logrotate:

/etc/logrotate.d/syslog to restart SendmailAnalyzer when maillog is rotated or create a cron job.

For example:

/var/log/cron /var/log/debug /var/log/maillog /var/log/messages /var/log/secure /var/log/spooler /var/log/syslog
{
   sharedscripts
   postrotate
        /bin/kill -HUP `cat /var/run/syslogd.pid 2>/dev/null` 2>/dev/null || true
/PATH_TO/rc.sendmailanalyzer restart >/dev/null 2>&1 || true
# or /etc/rc.d/init.d/sendmailanalyzer restart >/dev/null 2>&1 || true
   endscript
}

How to install darkstat in linux, centOS?

Darkstat - Web Based Network Traffic & Bandwidth Monitoring Tool on Linux

# yum install darkstat

# darkstat -i eth0

Test:

http://ip-address:667

How to install Monitorix in linux, centOS?

-->Monitorix is a lightweight system monitoring tool that can track services and resources of a system. This is one of the best tool to track system activities in simple and easiest way.

It can monitor system attributes like
-->System load
-->Active processes
-->Memory allocation
-->Kernel usage
-->Context switches and forks
-->VFS usage
-->Kernel usage per processor
-->Filesystems usage
-->Disk I/O activity
-->Inode usage
-->Time spent in I/O activity
-->Network traffic and usage
-->IPv4 states
-->IPv6 states
-->Active close
-->Passive close
-->UDP statistics
-->System services demand
-->IMAP and POP3 services
-->SMTP service
-->Network port traffic (Ports: 21, 22, 25, 80, 110, 139, 3306, 53, 143)
-->Users using the system
-->Devices interrupt activity


Installation Procedure

# yum install httpd rrdtool rrdtool-perl perl-libwww-perl perl-MailTools perl-MIME-Lite perl-CGI perl-DBI

Note: Some times on updated package this may not be enough, use the following command to update and download more packages to support the configurations.

# yum -y install rrdtool rrdtool-perl perl-libwww-perl perl-MailTools perl-MIME-Lite perl-CGI perl-DBI perl-XML-Simple perl-Config-General perl-HTTP-Server-Simple perl-IO-Socket-SSL

Download monitorix and install

# rpm -ivh http://www.monitorix.org/monitorix-n.n.n-1.noarch.rpm

After successful installations

# service monitorix start
#chkconfig monitorix on  ----> Add to startup

Log file: /var/log/monitorix

Testing:

http://ip-address:8080/monitorix/


Thats all, comments and suggestions are welcome!!

Download whole website using command

# wget -r --level=0 -convert-links --page-requisites --no-parent www.website.com

The wget options:
-r
--recursive, perform recursive
-l
--level=,Use 0 for infinite depth level or use number greater than 0 for limited depth.
-k
-convert-links,Modify links inside downloaded files to point to local files.
-p
--page-requisites, Get all images, css, js files which make up the web page.
-np
--no-parent, Don't download parent directory contents.