Note: Purpose of this question is to be a reference for anyone who has problem for upgrading their MySQL5.5 on LEMP 14.04 with 512MB / 1CPU size.

My droplet is created using LEMP 14.04 (One-click Apps) with 512MB/1CPU size. And this is by default will install Ubuntu 14.04 with Mysql 5.5.

mysql -V
mysql  Ver 14.14 Distrib 5.5.49, for debian-linux-gnu (x86_64) using readline 6.3

When I'am trying to upgrade the MySQL version to 5.6*, following error occur:

start: Job failed to start  
invoke-rc.d: initscript mysql, action "start" failed.  
dpkg: error processing package mysql-server-5.6 (--configure):  
 subprocess installed post-installation script returned error exit status 1  
Setting up libhtml-template-perl (2.95-1) ...  
Setting up mysql-common-5.6 (5.6.16-1~exp1) ...  
Processing triggers for libc-bin (2.19-0ubuntu6) ...  
Processing triggers for ureadahead (0.100.0-16) ...  
Errors were encountered while processing:  
 mysql-server-5.6  
E: Sub-process /usr/bin/dpkg returned an error code (1)

After hours of searching I found that the failure seems to be because of the default MySQL 5.6 configuration where it requires more memory than it can get in the micro instance. See bug report. See solution

So I’ve taken this steps to fix the errors.

• Step 1-Removing MySQL 5.5 Completely

  sudo service mysql stop  #or mysqld
  sudo killall -9 mysql
  sudo killall -9 mysqld
  sudo apt-get remove --purge mysql-server mysql-client mysql-common
  sudo apt-get autoremove
  sudo apt-get autoclean
  sudo deluser mysql
  sudo rm -rf /var/lib/mysql
  sudo apt-get purge mysql-server-core-5.5
  sudo apt-get purge mysql-client-core-5.5
  sudo rm -rf /var/log/mysql
  sudo rm -rf /etc/mysql
  

• Step 2-Create swap file
  Create a 4G swap file:

  sudo fallocate -l 4G /swapfile
  

  Change its permission to only root could access and change:

  sudo chmod 600 /swapfile
  

  Make it swap:

  sudo mkswap /swapfile
  

  Activate:

  sudo swapon /swapfile
  

• Step 3-Install new version of Mysql

  sudo apt-get install mysql-client-5.6 mysql-client-core-5.6
  sudo apt-get install mysql-server-5.6
  

That’s it! now lets check if the new version is installed

mysql -V
mysql  Ver 14.14 Distrib 5.6.31, for debian-linux-gnu (x86_64) using  EditLine wrapper