Basic-Concepts
Web Servers
Uptime
Internet
Programming
Version Control
Configuration Management
Virtualization
Databases
Mail Servers
Domain Name Servers
Some useful links to explain the concepts of Memory
http://blog.ioflood.com/2015/03/27/making-sense-of-linux-memory-usage-part-1-how-to-read-top-in-centos/
https://www.reddit.com/r/linux/comments/1hk5ow/free_buffer_swap_dirty_procmeminfo_explained/
http://corlewsolutions.com/articles/article-6-understanding-the-free-command-in-ubuntu-and-linux
http://www.linuxatemyram.com/
http://www.cloudibee.com/know-about-procmeminfo/
http://www.linuxnix.com/find-ram-details-in-linuxunix/
http://www.thegeekstuff.com/2010/08/ipcs-command-examples/
http://www.tecmint.com/dstat-monitor-linux-server-performance-process-memory-network/
http://github.com/pixelb/scripts/commits/master/scripts/ps_mem.py
https://www.jamescoyle.net/how-to/943-create-a-ram-disk-in-linux