My Ubuntu VM

Prereqs

Download and add all these to your system PATH.

Build the Base VM

Change the -var flags to suit your needs. When you run the Packer command, you should see a VirtualBox GUI window running boot commands, then the login prompt while Packer tasks continue running in the terminal. Wait for the Packer command to finish running.

With Bash:

cd bento/packer_templates/ubuntu
packer build -only=virtualbox-iso -var "disk_size=65536" -var "cpus=4" -var "memory=4096" ubuntu-20.04-amd64.json
cd ../../..

Or, with PowerShell:

cd .\bento\packer_templates\ubuntu
packer build -only=virtualbox-iso -var "disk_size=65536" -var "cpus=4" -var "memory=4096" ubuntu-20.04-amd64.json
cd ..\..\..

Add the Base Box as a Vagrant Box

vagrant box add ubuntu_base bento/builds/ubuntu-20.04.virtualbox.box

Build the Vagrant VM

vagrant up

Verify the VM's Specs Are What You Set in Packer

# Start an SSH session in the VM
vagrant ssh
# Check the available memory (RAM)
free -m
# Check the available disk space
df -h
# Check the number of available CPUs
nproc
# Leave the SSH session
exit

Setup SSH

If you use VS Code:

Download the Remote Development extension
Go to the Remote Explorer pane
Hover over SSH Targets and click the cog button (Configure)
Select the SSH config file you wish to edit.

If you don't use VS Code, just open your machine's ~/.ssh/config in an editor.

Copy the output of this command into your SSH config file...

vagrant ssh-config

Except...

Change Host default to Host ubuntu-vm.
Delete the UserKnownHostsFile /dev/null line if you're on Windows.