Install Discourse Forum with Nginx on Ubuntu 16.04

Step 1 – Install Docker on Ubuntu 16.04

The Discourse software is written in Ruby and Javascript, using PostgreSQL as the main database, and Redis as a cache and for transient data. We will install Discourse under the Docker container.
The installation process will be carried out on Ubuntu 16.04. So to begin with, install Docker using the command below.

wget -qO- | sh


After the installation is complete, check the docker service and make sure it’s already running on the system. Continue reading “Install Discourse Forum with Nginx on Ubuntu 16.04” »


Extend/Reduce LVM’s (Logical Volume Management) in Linux

My Server Setup – Requirements

  1. Operating System – CentOS 6.5 with LVM Installation
  2. Server IP –

How to Extend Volume Group and Reduce Logical Volume

Logical Volume Extending

Currently, we have One PV, VG and 2 LV. Let’s list them one by one using following commands.

# pvs
# vgs
# lvs

Logical Volume Extending

Logical Volume Extending

Continue reading “Extend/Reduce LVM’s (Logical Volume Management) in Linux” »


Endian Installation USB Flash Drive

This lesson describes how to create an installation USB drive for image files provided by Endian and to verify the integrity of the image file. The procedure applies to Windows users with XP, Vista, or Windows7 systems.


You need the following to complete this lesson:

  • .iso or .img image of an Endian Appliance.
  • md5sum of the image.
  • An USB Stick.

Some USB sticks may not work with Endian devices. In particular, some Endian hardware device might fail to recognise USB Sticks with size bigger the 2Gb. so you should try with one USB stick with smaller size.

Note: ISO image files
Starting with release 5.0, Endian releases installation images as .iso file, rather than .img. However, the following procedure and suggested software can be used also with .iso files.

It is assumed that you have an Endian image file and its correspondent md5sum checksum on your computer. This lesson takes as example an image of an edge 3.0 and its correspondent md5sum file saved in C:\:

In order to create the Endian installation USB flash drive you need to download an application that allows to burn img and iso images to USB flash drives disks, like win32 Disk Imager. Continue reading “Endian Installation USB Flash Drive” »


Zimbra GUI Customization- Logo, Title, Footer

To change logo (On Zimbra 8.6 and onwards)

zmprov md zimbraSkinLogoLoginBanner
zmprov md zimbraSkinLogoAppBanner

To change logo height:

changed hhe contents of file /opt/zimbra/jetty/webapps/zimbra/skins/_base/base3/

90 LoginH1 = margin:0 0 30px 30px;
91 LoginAppName = display:none;
92 LoginLabelColor = @TxtC@
93 LoginButton = @ButtonShadowDefault@ border:1px solid @ButtonBorderColor@;
94 LoginBannerImg = @LogoImgDir@/LoginBanner.png?v=@jsVersion@

//95 LoginBanner = @img(, LoginBannerImg, 450px, 36px)@ //old
95 LoginBanner = @img(, LoginBannerImg, 450px, 90px)@ //new

96 LoginFooterColor = color:@darken(AppC,55)@;
97 LoginErrorPanel = background-color:#FF9; padding:5px; @roundCorners(8px)@

Apply it-

zmmailboxdctl restart

Basic Email Server with Postfix, Dovecot and Squirrelmail on CentOS 6

Step 1 »Before installation assign a static ip and add a host entry for your domain to that IP in the /etc/hosts file like below.

Step 2 » Issue the below command to install postfix

[root@mail ~]# yum -y install postfix

Step 3 » Now issue the below command to install SMTP AUTH packages .

[root@mail ~]# yum -y install cyrus-sasl cyrus-sasl-devel cyrus-sasl-gssapi cyrus-sasl-md5 cyrus-sasl-plain

Postfix package installation is completed .

Step 4 » Issue the below commands one by one for creating SSL Cert.

[root@mail ~]# mkdir /etc/postfix/ssl
[root@mail ~]# cd /etc/postfix/ssl/
[root@mail ssl]# openssl genrsa -des3 -rand /etc/hosts -out smtpd.key 1024
[root@mail ssl]# chmod 600 smtpd.key
[root@mail ssl]# openssl req -new -key smtpd.key -out smtpd.csr
[root@mail ssl]# openssl x509 -req -days 365 -in smtpd.csr -signkey smtpd.key -out smtpd.crt
[root@mail ssl]# openssl rsa -in smtpd.key -out smtpd.key.unencrypted
[root@mail ssl]# mv -f smtpd.key.unencrypted smtpd.key
[root@mail ssl]# openssl req -new -x509 -extensions v3_ca -keyout cakey.pem -out cacert.pem -days 365

Step 4 » Now open /etc/postfix/ file Continue reading “Basic Email Server with Postfix, Dovecot and Squirrelmail on CentOS 6” »


DNS UDP Load Balancer using Nginx

The plan is to build a DNS- UDP load balancer DNS recursive server (actually forwarding service). The design logic is simple-

On client side a public recursive+forwarding DNS IP –> hits the Nginx Load Balancers  –> sends traffic to Google Public DNS/IBM Public DNS/Own recursive DNS/OpenDNS.

The configuration is quite simple on Nginx Load Balancer, the core configuration content is pretty straight forward:

# Load balance UDP-based DNS traffic across two servers
stream {
upstream dns_upstreams {

server {
listen 53 udp;
proxy_pass dns_upstreams;
proxy_timeout 1s;
proxy_responses 1;
error_log logs/dns.log;

Continue reading “DNS UDP Load Balancer using Nginx” »


Configure DHCP Server Step-by-Step config Guide Using Webmin

Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway.

In our previous article, you have setup your DNS Server using Webmin, refer below link for more information.

In this article We will seen how to configure DHCP Server Using Webmin(web-based interface). Webmin tool offer to new system administrators to perform all system management task from via a web browser, Instead of using the command line console or terminal. You can also manage a system from the console or remotely. Continue reading “Configure DHCP Server Step-by-Step config Guide Using Webmin” »