[manigandham]

You have a bunch of servers with kubernetes software installed on all of them. 1 of them is master, the rest are workers. You talk to Master through API and it talks to workers with SSH.

You send the Master some YAML files that list what containers you want running, how many, and lots of optional details. Master makes it happen so it matches what you said should be running.

Master also constantly checks everything so it matches what you asked for, even if something changes like a server failing. That's it.

[brianmcc]

Nice clear explanation. In the spirit of ELI5 I kind of think "container" is a terrible name for what seem to be super-lightweight VMs, I can't help thinking something like "instance" might have been better.

In the same way in OO languages we instantiate a class to get an object instance, containerisation seems to involve creating an instance (or several instances) of an image.

But I am really still learning all this stuff - I'm sure there's a reason behind it, and at the end of the day it's simply a set of terms one needs to absorb.

[manigandham]

Instance is probably more overloaded, but also abstract in this case. Container refers to the virtualization mechanism that is lighter than an entire operating system but still isolates several processes into their own environment.

Instance of VM image => Running VM

Instance of Container image => Running Container

[brianmcc]

That's fair enough, I guess it's just the fact that the term until very recently confused me rather than clarified things; I found it genuinely obfuscatory, as a developer with relatively light infrastructure experience.

Of course I have come to terms with the fact that by now it's entrenched so we're using it, end of story - give me a few more years and I'll be pretty much adapted to it :-)