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  A possible way to recover deleted files on Linux

Last week I was generating a MD5 sum for an virtual machine image on one OpenNebula server: # ls -l test.img -rw-r--r-- 1 root root 10486808576 Oct 12 02:21 test.img # md5sum test.img At the same time I was clearing the files on the server on another terminal and deleted the above image file mistakenly with : # rm test.img Since this image file is 10GB, it took some time to remove this file from the server, so I used the Ctrl+Z command to suspend the remove command. [1]+ Stopped ...

   Linux,File,Recovery     2013-11-26 07:03:37

  5 Ways to Boost MySQL Scalability

There are a lot of scalability challenges we see with clients over and over. The list could easily include 20, 50 or even 100 items, but we shortened it down to the biggest five issues we see.1. Tune those queriesBy far the biggest bang for your buck is query optimization. Queries can be functionally correct and meet business requirements without being stress tested for high traffic and high load. This is why we often see clients with growing pains, and scalability challenges as their site becom...

   MySQL,Scalability,Methods,Implementation,Practice     2011-10-18 02:57:27

  An experience on fixing HTTP 406 Not Acceptable error

This post is about an experience of mine on fixing a HTTP 406 Not Acceptable error seen on one of my page. Just got back from a business trip and opened my computer as usual to start to monitor my website statistics. But when I opened the page on showing real time page views, it shows nothing but zero. So I pressed F12 to bring up the developer tool to check on what's going on. The logic of loading the real time page view is backed by AJAX call. In the developer tool console, I see that the rAJA...

   PHP,AJAX,HTML,HTTP 406,CONTENT-TYPE     2019-03-30 04:09:10

  A HTTPS client and HTTPS server demo in Java

In this post, I will create a HTTPS server and HTTPS client demo which can establish HTTPS communication between a server and a client using Java. This should be very useful when we want to test our understanding about SSL communication. We will use both a detailed SSL client and a simple HttpsURLConnection as the HTTPS client. Before creating the actual HTTPS server and HTTPS client, we first need to generate the keystore and truststore to be used by the server and client. To generate the keyst...

   SSL,HTTPS,JAVA,DEMO     2015-10-23 09:04:36

  Fix WampServer offline issue

WampServer is a web server on Windows which provides easy to use features for PHP developers. You can easily setup a web server by installing WampSserver without much hard to understand configurations. After installing it and with a simple configuration, you just need to double click it and start all services and your server is gonna up.  If the server starts up normally, you will see a green icon which indicates the working status at the taskbar. But if you don't see the green icon shown u...

   APACHE,PHP,WAMPSERVER     2015-09-13 01:59:38

  Using public key authentication in SSH

SSH is a popular cryptographic network protocol for secure network service operation. It is frequently used in remote server login. For a system administrator or software developer, SSH is frequently used to access remote servers or development servers or testing servers etc.  To login with SSH, there are different authentication mechanisms : password, public key and interactive etc. If a remote server needs to be accessed frequently, password authentication may be too troublesome as p...

   LINUX,DEBUG,SSH,PUBLIC KEY     2016-09-10 05:55:46

  Get Facebook, Twitter and YouTube back

Facebook, Twitter and YouTube have become part of many people's daily network life. People hang around these sites to network with known and unknown friends, to know about the latest news and to relax with fancy video clips. But what will you feel if all of a sudden you cannot access them? Want to experience this? Go behind the GFW(Great Firewall) of China. Just a joke, but it's real. Huh, you are out of China? Don't worry. Change your DNS server to those located in China. I just experienced it,...

   DNS spoofing, GFW, YouTube, 37.61.54.158     2014-12-20 21:41:34

  Generate certificate in Java -- Self signed certificate

This is the first post in this series which I will show you how to generate SSL certificate in Java programmatically. Certificates are frequently used in SSL communication which requires the authentication of server to client. This is to make the client to trust that the server is actually the one it claims. Certificates are really important on the Internet. All HTTPS communications on the Internet need the server side to present their certificates signed by trusted CAs. The basic flow of a requ...

   Java,Certificate,X509     2014-07-30 07:42:18

  A guide on installing and setting up GitLab server on Ubuntu

GitHub, GitLab and BitBucket are the three most famous code hosting platform in the world. They have different features which allow teams or individuals to share code with others remotely. In case you want to build your own code hosting server so that you can host and share the code by yourself, you can install and set up your own server. In this post, we will walk you through a guide on installing and setting up GitLab server on Linux environment. gitlab is a web based code hosting tool which i...

   UBUNTU,TUTORIAL,GITLAB     2020-04-25 07:05:33

  The basics of Client/Server socket programming

  While Client/Server communication model is ubiquitous nowadays, most of them involve socket programming knowledge. In this post, I will introduce some rudimentary aspects of it: (1) Short/Long-lived TCP connection.Short-lived TCP connection refers to following pattern: Client creates a connection to server; send message, then close the connection. If Client wants to transmit information again, repeat the above steps. Because establishing and destroying TCP s...

       2017-09-26 19:43:10