• Category Archives Linux
  • .bashrc or .bash_profile?

    When working with Linux, I always forget which bash config file to edit when I want to set my PATH and other environmental variables for my shell. Should you edit .bash_profile or .bashrc in your home directory?

    You can put configurations in either file, and you can create either if it doesn’t exist. But why two different files? What is the difference?

    According to the bash man page, .bash_profile is executed for login shells, while .bashrc is executed for interactive non-login shells.

    What is a login or non-login shell?

    When you login (type username and password) via console, either sitting at the machine, or remotely via ssh: .bash_profile is executed to configure your shell before the initial command prompt.

    But, if you’ve already logged into your machine and open a new terminal window (xterm) inside Gnome or KDE, then .bashrc is executed before the window command prompt. .bashrc is also run when you start a new bash instance by typing /bin/bash in a terminal.

    Why two different files?

    Say you’d like to print some lengthy diagnostic information about your machine each time you login (load average, memory usage, current users, etc). You only want to see it on login, so you only want to place this in your .bash_profile. If you put it in your .bashrc, you’d see it every time you open a new terminal window.

  • Setting Up Cacti on Redhat/CentOS/Fedora

    Cacti is a network graphing tool similar to MRTG. How do I install and configure common options to collect SNMP data and various other data (such as system load, network link status, hard disk space, logged in users etc) into an RRD?

    From the official project site:

    Tutorial details
    Difficulty Easy (rss)
    Root privileges Yes
    Requirements None
    Estimated completion time 20m

    Cacti is a complete frontend to RRDTool, it stores all of the necessary information to create graphs and populate them with data in a MySQL database. The frontend is completely PHP driven. Along with being able to maintain Graphs, Data Sources, and Round Robin Archives in a database, cacti handles the data gathering. There is also SNMP support for those used to creating traffic graphs with MRTG.

    Required software(s)

    You need to install the following software on RHEL / Fedora / CentOS Linux:

    1. MySQL Server : Store cacti data.
    2. NET-SNMP server – SNMP (Simple Network Management Protocol) is a protocol used for network management.
    3. PHP with net-snmp module – Access SNMP data using PHP.
    4. Apache / lighttpd / ngnix webserver : Web server to display graphs created with PHP and RRDTOOL.

    Install the Cacti software on CentOS / RHEL

    First, login as root user and type the following command to install mysql, apache and php:
    # yum install mysql-server mysql php-mysql php-pear php-common php-gd php-devel php php-mbstring php-cli php-snmp php-pear-Net-SMTP php-mysql httpd

    Configure MySQL server

    First, set root password:
    # mysqladmin -u root password NEWPASSWORD

    Create cacti MySQL database

    Create a database called cacti, enter:
    # mysql -u root -p -e 'create database cacti'
    Create a user called cacti with a password called zYn95ph43zYtq, enter:
    # mysql -u root -p

    mysql> GRANT ALL ON cacti.* TO [email protected] IDENTIFIED BY 'zYn95ph43zYtq'; 	
    mysql> FLUSH privileges;
    mysql> \q

    Install snmpd

    Type the following command to install net-snmpd
    # yum install net-snmp-utils php-snmp net-snmp-libs
    Configure snmpd, open /etc/snmp/snmpd.conf
    # vi /etc/snmp/snmpd.conf
    Append / modify it as follows (see snmpd.conf man page for details):

    com2sec local     localhost           public
    group MyRWGroup v1         local
    group MyRWGroup v2c        local
    group MyRWGroup usm        local
    view all    included  .1                               80
    access MyRWGroup ""      any       noauth    exact  all    all    none
    syslocation Unknown (edit /etc/snmp/snmpd.conf)
    syscontact Root  (configure /etc/snmp/snmp.local.conf)
    pass . /usr/bin/ucd5820stat

    Save and close the file. Turn on snmpd service:
    # /etc/init.d/snmpd start
    # chkconfig snmpd on

    Make sure you are getting information from snmpd:
    # snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex
    Sample ouptut:

    IP-MIB::ipAdEntIfIndex. = INTEGER: 2
    IP-MIB::ipAdEntIfIndex.67.yy.zz.eee = INTEGER: 3
    IP-MIB::ipAdEntIfIndex. = INTEGER: 1

    Install cacti

    First, make sure EPEL repo is enabled. Type the following command to install cacti:
    # yum install cacti

    Install cacti tables

    Type the following command to find out cacti.sql path:
    # rpm -ql cacti | grep cacti.sql
    Sample output:


    Type the following command to install cacti tables (you need to type the cacti user password):
    # mysql -u cacti -p cacti < /usr/share/doc/cacti-0.8.7d/cacti.sql

    Configure cacti

    Open /etc/cacti/db.php file, enter:
    # vi /etc/cacti/db.php
    Make changes as follows:

    /* make sure these values refect your actual database/host/user/password */
    $database_type = "mysql";
    $database_default = "cacti";
    $database_hostname = "localhost";
    $database_username = "cacti";
    $database_password = "zYn95ph43zYtq";
    $database_port = "3306";

    Save and close the file.

    Configure httpd

    Open /etc/httpd/conf.d/cacti.conf file, enter:
    # vi /etc/httpd/conf.d/cacti.conf
    You need to update allow from line. Either set to ALL or your LAN subnet to allow access to cacti:

    # Cacti: An rrd based graphing tool
    Alias /cacti    /usr/share/cacti
    <Directory /usr/share/cacti/>
            Order Deny,Allow
            Deny from all
            Allow from

    Another option is create /usr/share/cacti/.htaccess file and password protect the directory. Finally, restart httpd:
    # service httpd restart

    Setup cacti cronjob

    Open /etc/cron.d/cacti file, enter:
    # vi /etc/cron.d/cacti
    Uncomment the line:

    */5 * * * *     cacti   /usr/bin/php /usr/share/cacti/poller.php > /dev/null 2>&1

    Save and close the file.

    Run cacti installer

    Now cacti is ready to install. Fire a webbrowser and type the url:
    Just follow on screen instructions. The default username and password for cacti is admin / admin. Upon first login, you will be force to change the default password.

    How do I configure SNMP data collection?

    SNMP can be used to monitor server traffic. Once installed login to cacti.
    => Click on Devices

    => Select Localhost

    => Make sure SNMP options are selected as follows:

    Fig.01: SNMP configuration

    Fig.01: SNMP configuration

    Finally, click on Save button.

    How do I create SNMP graphs?

    Click on “Create Graphs for this Host” link on top right side.

    Select SNMP – Interface Statistics

    Select a graph type (such as In/Out bytes with total bandwidth)

    Finally, click on Create button.

    How do I view graphs?

    To view graphs click on Graphs tab. Here is sample graph from one my own box:

    Fig.02: Cacti in Action - Memory, CPU and Network Usage

    Fig.02: Cacti in Action – Memory, CPU and Network Usage

    (Fig.02: Cacti in action)

    Fig.03: Cacti in Action Disk, Load average and User stats

    Fig.03: Cacti in Action Disk, Load average and User stats