How to check memory usage per process in linux?

When you feel that your linux server is running slow, you properly run top command to check the how many memory have been used. But it just shows the overall memory usage. To show memory usage per process, you can run this command ps aux --sort -rss

By | August 25th, 2018|IT Knowledge Base|0 Comments

Upgrade MySQL from 5.5 to 5.7 on Debian

In a few months ago, I tried to Upgrade MySQL from 5.5 to 5.7 on CentOS. Although the upgrade process is successful, it is a little bit terrible experience because all data may be removed. Recently, I have got another request to the same upgrade but in Debian. The process is definitely much easier. I [...]

By | July 19th, 2016|IT Knowledge Base|0 Comments

Upgrade MySQL from 5.5 to 5.7 on CentOS

I have got a task to migrate a system from a CentOS server and another CentOS server. When I imported the MySQL database to the server, I have got the following error: (SQL Error: 1294 SQL State: HY000) - Invalid ON UPDATE clause for 'column_name' field Oh.... DATETIME can use CURRENT_TIMESTAMP on update starting from [...]

By | April 29th, 2016|IT Knowledge Base|0 Comments

Centos: PHP Fatal error: Class ‘SoapClient’ not found in

You may get an error returned from error log (example from CentOS): PHP Fatal error:  Class 'SoapClient' not found in   Create a php file (e.g. info.php) with the following code in your server : <?php phpinfo();?>   Access to the page (e.g. and check whether the soap is installed and enabled Or You [...]

By | January 7th, 2016|IT Knowledge Base|0 Comments

CentOS: apr_sockaddr_info_get() failed for XXXXX

You may get the error when restarting apache. # service httpd restart Stopping httpd: [ OK ] Starting httpd: httpd: apr_sockaddr_info_get() failed for XXXXX httpd: Could not reliably determine the server's fully qualified domain name, using for ServerName It is because of the apache variable ServerName has not been set. In CentOS, you can [...]

By | December 5th, 2015|IT Knowledge Base|0 Comments

How to restrict access to website?

Reference: You can protect a directory in Apache on Linux by using .htaccess file. It requires apache authentication to access to the website. Step 1: Setup Apache Authentication Create a folder to store apache authentication # mkdir /mnt/secure_pass_folder # chown apache:apache /mnt/secure_pass_folder # chmod 775 /mnt/secure_pass_folder Add a user and password of apache authentication # htpasswd [...]

By | December 30th, 2014|IT Knowledge Base|0 Comments

Check if your Linux server is 64 bit or 32 bit

In order to check if your Linux server is 64 bit or 32 bit, you can run the following command. uname -a If the output has "i686" or "i386", the linux server is 32-Bit. If the output has "x86_64", the linux server is 64-bit   Reference:

By | November 28th, 2014|IT Knowledge Base|0 Comments

How to connect MSSQL in PHP on Linux

You may want to connect to your Microsoft SQL database (MSSQL) by the applications in your Linux server. This article describes the steps to install the php modules php-mssql on CentOS 6 with PHP 5.3   Step 1 - Install required packages (freetds and php-mssql) The module php-mssql is not in the default repository.  So [...]

By | November 25th, 2014|IT Knowledge Base|0 Comments

How to compare files in two folders in Linux by md5sum?

When a website is hacked, one of next actions is to clean up the hacked files. The hackers may upload new files through the security vulnerability, or they may modify the files to insert some codes (almost on the top or bottom of the files).   If you want to check if files are updated [...]

By | August 19th, 2014|IT Knowledge Base|0 Comments