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  How does computer boot up?

The whole boot process of computer can be summarized in 4 phases. 1. BIOS In the 70's  read-only memory(ROM) was invented. The boot program is written into ROM, the first thing the computer does is to read and execute this program when it's powered on. The program in this chip is called "Basic Input/Output System" (BIOS). 1.1 Power-On Self-Test The BIOS will first check whether the computer hardware can fulfill the basic conditions for booting up, this process is called Power-On Self-Test...

   Computer, boot, partition     2013-02-23 23:19:47

  Using Fabric to deploy web app

Many people may use FTP and rsync to synchronize codes to server, this way is fine but it may be troublesome when you need to deploy many times a day, actually there is a simple way if you can spend time on finding the fast way. We introduce Fabric today for deploying web app to remote server. Fabric is a deployment tool written with Python, the biggest feature if it is you no need to login to remote server, you can execute remote commands locally. Here is s simple deployment script written with...

   Fabric, Web deployment,SSH,Python     2012-12-08 03:16:00

  Software Development Company Shares Its Development Process

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   CUSTOM SOFTWARE DEVELOPMENT COMPANY,SOFTWARE ARCHITECHURE,TESTING,REQUIREMENT ANALYSIS,MAINTENANCE     2016-01-21 00:13:26

  How expensive is a MySQL query?

Database access speed is always the bottle neck of many applications. Many application have large amount of data to search, retrieve and display nowadays. How do we improve the performance of our applications, how do we reduce the cost of database access? Apart from the design of database, the quality of the query is also one important factor to take care.  But before that, we need to know how much network traffic a query will consume. Yunyang,Zhang from Nubee in Singapore did some research...

   MySQL,Network traffic,Query     2013-04-09 05:13:33

  Memory related exception analysis in Java

Java Virtual Machine Specification divides the memory of JVM into several areas : Heap, Stack, The Program Counter register and Method area etc. In HotSpot JVM, heap is composed of Young, Tenured and Perm. There are different OutOfMemory error can happen in different memory area. Next is an overview of some of these OOM errors. StackOverflowError The JVM will allow only a specified number of stacks created nested. An JVM option -Xss can be set to determine the maximum stack size. If the num...

   Java, Memory model, Memory exception, OOM     2015-01-19 06:54:27

  How to commit code to OpenStack

If you want to make contributions to OpenStack, the best way to start is to help the community with blueprint or submit bug fix. To commit codes, you need to conform to some rules in the community. Work flow Register an OpenID Apply for a CLA certificate Apply for company CLA certificate Update contributor list Join OpenStack Contributors group and OpenStack group Set up SSH Keys Get a blueprint/bug git clone codes to local disk. Configure user name and user email and openid Modify codes in a l...

   OpenStack,Contribution     2013-08-04 23:04:45

  A plugin to update last_error in Delayed Job

delayed_job is a process based asynchronous task processing gem which can be ran at background. It will fork the specified number of processes to execute the tasks asynchronously. The task status is usually stored in the database so that it can be easily integrated into a Rails application where asynchronous job execution is desired. Normally when a job fails to execute or error occurs, it would save the error into the database with the column last_error. Ideally all these will be handled b...

   RUBY,RUBY ON RAILS,DELAYED JOB,LAST_ERROR     2017-11-18 13:05:49

  Linux Clock : CST,UTC and NTP setup

1. There is an option when you set up clock on installing Linux: system clock users UTC, so what does UTC mean? It's Universal Time Coordinated(UTC), there are two different times in GPS system: one is UTC , the other one is LT(Local Time). The difference between these two is just the timezone difference, UTC is the time in timezone 0. If the local time in Beijing is 8 o'clock in the morning, then UTC time is 0 o'clock, which is a 8 hour difference. 2. In Linux, when we use date to check the tim...

   Linux,Clock,UTC     2013-03-21 12:19:30

  Resolving error "SSL certificate problem: self signed certificate in certificate chain"

In a PHP application, cURL is frequently used to make connection to remote server to request some resource. It can be used to transfer data with different protocols such as HTTP, HTTPS, FTP etc. While using cURL in PHP, someone may get an error with message similar to "SSL certificate problem: self signed certificate in certificate chain". This may happen when cURL tries to make a SSL connection server and the server returns a server certificate which is self-signed and it's not trusted by the c...

   PHP,SSL,CURL,TWILIO     2016-06-26 07:17:23

  9 reasons to use Zsh

Like majority *nix users, I have been using bash for many years. Sometimes I feel uncomfortable with bash. I tried use some other shells as well such as ksh, tcsh and zsh which I am going to talk about. A few days ago, I found an open source project ranking in the 6th named oh-my-zsh on Github, I downloaded it and had a try with it. It's amazing. We should use zsh to replace bash now. Why do we need to use zsh? Here is a 4 minutes YouTube video which shows many reasons why we should switch from ...

   zsh, advantage, command     2012-09-28 12:46:39

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