Issue
In the AWS website https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/user-data.html, it shows how to modify the instance user data of an existing EC2.
However, at the end it says the modified user data will not be executed (7). What's the point to modify the user data and not executed? Is it possible to execute the modified user data once?
To modify instance user data
Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
In the navigation pane, choose Instances.
Select the instance and choose Instance state, Stop instance. If this option is disabled, either the instance is already stopped or its root device is an instance store volume.
When prompted for confirmation, choose Stop. It can take a few minutes for the instance to stop.
With the instance still selected, choose Actions, Instance settings, Edit user data.
Modify the user data as needed, and then choose Save.
Restart the instance. The new user data is visible on your instance after you restart it; however, user data scripts are not executed.
Solution
The User Data field was created as a way to pass information to an instance. For example, providing a password to a database, or configuration information.
Then, the Ubuntu community came up with the clever idea of passing a script via the User Data field, and having some code on the instance execute the script when the system boots. This has enabled "self-configuring" systems, and is called cloud-init.
By default, the User Data script only executes once per instance, with the intention of installing software.
From Boot Stages — cloud-init documentation:
cloud-init ships a command for manually cleaning the cache:
cloud-init clean
Running this command will 'forget' the previous runs, and will execute the User Data script on the next boot.
It is also possible to run a script on every boot by placing the script in /var/lib/cloud/scripts/per-boot/.
Answered By - John Rotenstein Answer Checked By - Senaida (WPSolving Volunteer)
