Virtual Machines and Containers

This is an extra note from the 2019 version.

Virtual Machines#

• To experiment with operating systems, software and configurations without risk.
  • running a software that only runs on a certain operating system
  • experimenting potentially malicious software

Useful Featrues#

• Isolation: hypervisors isolate the guest from the host
• Snapshots: you can take snapshots of the virtual memory, capturing the entire machine state and then restore to an earlier state.
  • Useful to test out potentially destructive operations

Disadvantages#

• Slower than running on bare metal

Resources#

• Hypervisors
  • VirtualBox
  • Virt-manager
  • VMWare

Containers#

• VMs are heavy-weight, containers allow you to spin up machines in an automated fashion. Containers have higher performance but less secure and isolated than VMs.
  • Amazon Firecracker
  • Docker
  • rxt
  • lxc
• Containers: an assembly of various Linux security features to give the appearance of virtualization
  • virtual file system
  • virtual network interfaces
  • chroot
  • virtual memory tricks
• The difference betweem VMs and containers:

• Containers are handy when you want to run an automated task in a standardized setup. Sometimes a machine needs to run many services with conflicting dependencies, then they can be isolated by containers.
  • Build systems
  • Development environments
  • Pre-packaged servers
  • Running untrusted programs
    • Grading student submissions
    • Cloud computing
  • Continuous Integration (CI)
    • Travis CI
    • Github Actions
• Workflows
  • A minimal base image (Alpine Linux)
  • A list of commands to run to set up the environment you want (install package, copy files and build stuff)
  • Specify external ports that should be availble, an entrypoint that dictates what command should be run when the container is started.
• DockerHub has many software services have prebuilt images that one can easily deploy