Enumerating aws tags with aws cli

Question

I was thinking I could add a tag to my AWS machines, for example

Key: Backup Value: 00 04 * * *

and then from our management server use this to schedule volume snapshots at certain times. So far I'm struggling with jmespath stuff, and I can't seem to get my head around the json path extraction syntax:

aws ec2 describe-instances --query 'Reservations[].Instances[].Tags[?Key==`Backup`]'
[
   [],
   [],
   [],
   [],
   [
       {
           "Value": "00 04 * * *",
           "Key": "Backup"
       }
   ],
   [],
   []
]

I could use some help to work out how to extract the following two values, provided the Backup tag is defined for the instance.

InstanceId, Value of the Backup key

Answer 1

Try just querying the tags, specifying that you only want tags for instances, and that you want the value of the field "key" to be "Backup". (Example below)

aws ec2 describe-tags --query "Tags[*].{Backup:Value,InstanceId:ResourceId}" --filters "Name=resource-type, Values=instance" --filters "Name=key,Values=Backup" --output table 

(the output in this example is table for easy viewing of results, but you can change it to json or text as needed.)