Linux: netstat command

netstat (network statistics) is a command used for monitoring network connections (incoming & outgoing) as well as viewing routing tables, interface statistics etc. netstat is available on all Unix-like Operating Systems and also available on Windows operating system.

Features:
a. Useful in terms of network troubleshooting (traffic, ports, network connections), networking statistics and performance measurement.
b. netstat is one of the most basic network service debugging tools, telling you what ports are open and whether any programs are listening on ports.
c. provide detailed information about how a computer is communicating with other computers or network devices.

Grant Users Access to your Outlook Calendar

Outlook Calendar -  a very powerful tool to manage your emails, appointments, meetings, calendars, notes, contacts etc. Everyone has used the Outlook product of Microsoft, which has really made our lives easy. We all know that we can schedule our appointments and send meeting invitations in Outlook calendar but today we are going to reveal another trick to grant user access to our calendar so that other person (having permission) can edit our calendar. You must open Microsoft Outlook to perform the steps below:

Error: Could not open command file ‘/usr/local/nagios/var/rw/nagios.cmd’ for update!

Error: Could not open command file ‘/usr/local/nagios/var/rw/nagios.cmd’ for update!,An error that comes up from time to time and is quite annoying to deal with, I found a way to fix the problem, it is not the best way, but it is simple and fast.

Apache : James - Generating Users list

We have gone through about James server in previous post. In this post, we'll see how to generate user list from James Server.
James server provides a very good utility to check the users list on the server. Either we can see the user list on the console or we can redirect the userlist in any text file.  This article contains the steps to generate the user list from James server:

Apache: James Server

The Apache Java Mail Server Version 3.0 is a 100% pure Java SMTP, IMAP4 and POP3 Mail server designed to be a complete and portable enterprise mail engine solution. Apache James Server is based on currently available open protocols. 
Advantages
a. Standard

• 100% pure Java Mail server designed to be a complete and portable enterprise mail engine solution.
• Supports currently available IETF protocols, including SMTP, LMTP, POP3 and IMAP4.
• Apache James Server is able to store user and message data either in a file-system (Maildir), any JPA-compatible database and even JCR, allowing fast, reliable, even real-time replicated storage.
• Provides a powerful, flexible mail application engine through support for the Apache Mailet API. With its Mailet pipeline architecture, Apache James Server can be used not only to provide standard e-mail services, but also to implement custom e-mail applications.

Ubuntu: Segmentation fault (core dumped)

Segmentation fault: Generally such kind of errors are caused by addressing non-existent/allocated memory location. Today I encountered this error while executing "apt-get install" command.

   root@gh008:~# apt-get install binutils
   Segmentation fault (core dumped)

 

I googled around for this issue and finally got two solution for this problem. 

MySQL: Database Backup and Restore Using Command Line

MySQL, one of the most commonly & widely used database in world for web applications. Its popularity for use with web applications is closely tied to the popularity of PHP, which is often combined with MySQL. Several high-traffic web sites use MySQL for its data storage and logging of user data, including Flickr, Facebook, Wikipedia, Google, Nokia and YouTube.

MySQL provide a great command line utility to take backup of your MySQL database and restore it. mysqldump command line utility is available with MySQL installation (bin directory) that can be used to take backup of databases and perform various task using command line. 

MySQL Master Slave Replication

MySQL replication is a process that allows us to easily maintain multiple copies of a MySQL data. MySQL data get automatically copied from a master to a slave database. This concept is helpful for many reasons including 
a. Automatically backing up for the data.
b. Providing alternate database server if master server get crashed somehow.
To check the replication status in Master Slave environment (MySQL). Just need to follow these steps:

Steps to work with GIT for dummies

Today I start working with BitBucket (GIT) and found it bit difficult in comparison to SVN. I  have to read lots of documentations to work with GIT and finally I succeed in it. But I made a note of all the steps for the beginners. Follow these steps and play with GIT.

Nagios: Unable to check HTTPS service using check_http

Nagios is a powerful IT infrastructure monitoring solution available in market. It provides monitoring graphically. I installed Nagios Core on a server and after the completion of nagios configuration, I checked that Nagios is not able to ping the host on which https is enabled. 

Configure Gmail SMTP Relay

SMTP stands for Simple Mail Transfer Protocol, lets you send email messages through your email account using your existing email service. This email service is subject to your interest. It could be any like: Gmail Relay, Snail Mail etc.

In this post we are going to configure Gmail Relay to send emails.

Nagios HTTP WARNING: HTTP/1.1 403 Forbidden Solved

I setup a nagios server and after the setup, I encounter a warning "Nagios HTTP WARNING: HTTP/1.1 403 Forbidden".

Nagios Server Configuration for different hosts

In our previous posts, we learn how to install nagios, how to install NRPE or NSClient++. Now let's have a look on configuring hosts in nagios in best practical way Nagios Server Configuration for different hosts.

It will be good practice if we configure the client hosts in groups on Nagios Server.

Steps to Group clients servers:

1. Create locations for host configuration files:

In our configuration, we are grouping servers in 4 main categories:

Nagios NRPE Installation

In previous article, we learn how to install nagios (monitoring tool). Now we'll learn how to install nagios agent on the system, which needs to be monitored in nagios. This Agent tool is known as Nagios NRPE (for linux). To monitor system having Windows operating system, we need to install NSClient++. NSClient++ is very easy to install as it is simply a .exe file. Here are the steps to install NRPE plugin (agent) on linux machine:

Nagios Installation

NAGIOS: It's a monitoring tool used widely in server administration. When we have large no. of system like in data centers then we need some technology to monitor our data base servers, application servers, routers, other machines etc. 

Nagios provides a complete solution for this. Nagios provides graphical reports and monitoring of our network & servers. In order to setup nagios successfully, we need to install nagios on one server and different machines, servers will be configred in it. To communicate with configured hosts (servers), we need to install NRPE agents on servers, which need to be monitored. 

Basic JQuery Interview Questions

Is jQuery a library for client scripting or server scripting?
Ans: Client scripting

Is jQuery a W3C standard?
Ans: No

What are jQuery Selectors?
Ans: Selectors are used in jQuery to find out DOM elements. Selectors can find the elements via ID, CSS, Element name and hierarchical position of the element.
• jQuery Selectors are used to select one or a group of HTML elements from your web page.
• jQuery support all the CSS selectors as well as many additional custom selectors.
• jQuery selectors always start with dollar sign and parentheses: $()
• There are three building blocks to select the elements in a web document.