Obtain a list of image and plan types using Linode API/CLI?

While I'm not very familiar with the API myself, as I don't do a lot of actual programming, I do use the Linode CLI in Bash scripts quite a bit, and this can also be found very easily using that tool. If you have the Linode CLI installed, you can list the available image and plan types using the commands:

linode-cli images list
linode-cli linodes types

These commands will list all of the values that you would need for assigning the 'image' and 'type' variables. With 'linode-cli' commands, you are also able to easily use tools like 'grep' and 'awk' to obtain specific pieces of data by appending your 'linode-cli' commands with the '--text' flag. For example, to get a Linode's ID number and assign it to a variable, assuming the Linode's label lives in the variable $Label:

LinID=$(linode-cli linodes list --text | grep "${Label}" | awk '{print $1}')

You can also figure out the plan types by following the format (leave out the ''):

planGeneration-planClass-numberOfvCPUs

For example:

1GB Nanode (1 vCPU):

g6-nanode-1

2GB Linode (1 vCPU) or 4GB Linode (2 vCPUs):

g6-standard-1
g6-standard-2

300GB High Memory Linode (16 vCPUs):

g6-highmem-16

Linode images work similarly, and follow the format:

source/os_version

For example:

A Linode-supplied Ubuntu 16.04 LTS or Fedora 28 image:

linode/ubuntu16.04lts
linode/fedora28

A custom install from a saved image on your account titled 'savedimage':

private/savedimage

You can also find our documentation on obtaining a list of images here,
as well as a list of plan types here. These links lead to the relvant pages of the Linode APIv4 documentation.

I'm late to this party, but the documentation for the API and CLI covers this:

List images is here

List types is here