This is a userdata script for a fairly particular use case: mapping volumes to drive letters based on EC2 tags.
It's an extension of the EC2Config option to always mount a drive with a particular label to a particular drive letter.
The problem with that is that the drive has to have a particular label. Now, generally that's not a big deal. You're setting up something like that because you are passing drives on EC2 EBS volumes around between multiple instances.
However, it might be nice, especially if the first stage of your processing pipeline is to generate the data on the volumes in the first place, to be able to start with an empty block device and have it initialized and mounted to the correct place. Hence this project.
The script-running functionality is in place so you can just create an AMI with a C:\Scripts\Startup directory and ignore the Windows Scheduler, which if you want to spend as little time as possible logged into the instance, is handy.
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Create an instance with an attached role. The role needs to be able to examine the instance, examine the attached EBS volumes, and read the tags on those volumes. The existing Amazon policies ReadOnlyAccess or AmazonEC2ReadOnlyAccess are certainly broad enough, but could be tightened if you want to. This is in Step 3: Configure Instance Details, if you're launching a new instance from the console.
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Put the Powershell script between
<powershell></powershell>tags, and put that in the User Data field of a Windows instance you're launching. It's in Step 3: Configure Instance Details, down at the bottom inside Advanced Details, if you're using the console. -
For all the EBS volumes you want to automount, add a DriveLetter tag and a DriveLabel tag. The DriveLetter should be a Windows drive letter, and as such, should be in the range D: to Z: -- it should end in a colon, and you don't get to do this to the boot drive or either of the floppy drives. The Drive Label should follow Windows naming conventions for disk volumes; since an empty EBS volume will be partitioned with a single partition taking up the whole volume, and will be formatted with NTFS, this only means, keep it under 32 characters.
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Start (or restart) the instance with the tagged EBS volumes attached. When the instance is up and you connect to it, you will see that it has drives, labelled with the DriveLabel tag, mounted at the letters specified with the DriveLetter tag.
Create a directory called C:\Scripts\Startup. Put scripts you want to run at instance start time in there. They will be run in lexical-sort order, and must be Powershell scripts with a .ps1 extension. There is no error handling on these.
This only works with Amazon EC2. The drive mapper only works with EBS volumes. The startup script execution is remarkably simple-minded.