OpenSSL generates keys

Sometimes, you have to generate the keys for your projects. You can use the coomand below:

Create a Private CA

Public CA

Sign Keys




PostgreSQL Command Line

There are many different between MYSQL and PostgreSQL. One of them is PostgreSQL is Command Lines.  I write as below for the reference as needed.


What motivates me? The fear of being average

Show databases

Connect to database

List all tables

Show table schema

Dump a table

Import a table or database:

Time comparison:


Backup Cassandra to S3 SWS

This post is just a small post. I would like to show you a way to incremental backup Cassandra to S3. In my case, I use a opensource named Cassandra_Snapshorter.

To know how to install it in your machine, you can refer to

Now, we create a backup script

After that, We will create a job in Crontab to run backup every night.

Convert WMV to MP4 in Ubuntu

Sometime, I use EZVID to create a video. The size of the file created by EZVID usually is bigger than my expectation. So I have to use avconv command to convert that video.

To install avconv in Ubuntu Server, we use command:

To convert the file, we use the command below: