Virtual Machines vs. Docker Containers

Virtual machine

• Each machine gets its own full guest operating system

• Including the kernel. The kernel is like the core of the operating system. The bit that controls the low level stuff.

• This is quite resource heavy on the host machine (The computer running the virtual machine)

• As a result of this it:

  • Needs to “boot” the guest Os

  • Is resource heavy

Hint

You can think of a Virtual Machine as a self contained computer packed into a single file. A hypervisor is capable of running such a file. There are two types of hypervisors:

• Type 1: direct interfacing with the infrastructure - e.g. HyperKit (OSX) / HyperV (Win)

• Type 2: runs as an application on the host Os - e.g. VirtualBox / VMWare / Parallels Desktop

Containers

• They all use the host machines kernel

• Everything on top of that is still isolated as that makes the distribution unique

• All distributions of linux (centos, ubuntu, debian, etc) are all build on the same kernel

• Docker uses special features of the unix file system to create isolated environments

• A container is a compromise in isolation and sharing

• The separation and sandbox-ing is not quite as extreme

• As a result of this it:

  • Uses (much) less resources

  • Can startup in milliseconds

  • Take up less disk space

  • Use less memory