Many people suffer from mental illness (1 in 4), but their suffering is mostly invisible, so we underestimate how many people feel the same as we do. 1 in 10 attendees last year made use of the offer of free counselling slots.
Puppet is an extremely useful, powerful and hyped tool for configuration management. Foreman provides a web frontend for Puppet (among other things) and is also capable of interfacing with virtualization tools to create new hosts. Both Puppet and Foreman are extremely useful in modern System Administration, but both of their documentation is kind of wide-spread and not as comprehensive as one might hope. That's why I'll do a writeup on how to install Foreman on top of an existing (and working) Puppet Master.
The Master/Slave pattern is a very common design pattern in software engineering. Interestingly enough, there are two different patterns called Master/Slave, one primarily used in distributed computing, the other mostly found in the field of databases. There are some other uses of the term and discussions on the subject which are explained in the end.
tl;dr: ADT: definition of a stack as
data + push + pop + peek. Data Structure: implementation of a stack as
linked list + push() + pop() + peek().
There is a difference between ADT (abstract data types) and data structures. Understanding it is necessary for getting the following articles about both abstract data structures and data types.