Issue using Terraform EC2 Userdata - bash

Question

I am deploying a bunch of EC2 instances that require a mount called /data, this is a seperate disk that I am attaching using volume attach in AWS.
Now when I did the following manually it works fine, so the script I use works however when adding it via userdata I am seeing issues and the mkfs command is not happening.
If you see my terraform config:
resource "aws_instance" "riak" {
count = 5
ami = "${var.aws_ami}"
vpc_security_group_ids = ["${aws_security_group.bastion01_sg.id}","${aws_security_group.riak_sg.id}","${aws_security_group.outbound_access_sg.id}"]
subnet_id = "${element(module.vpc.database_subnets, 0)}"
instance_type = "m4.xlarge"
tags {
Name = "x_riak_${count.index}"
Role = "riak"
}
root_block_device {
volume_size = 20
}
user_data = "${file("datapartition.sh")}"
}
resource "aws_volume_attachment" "riak_data" {
count = 5
device_name = "/dev/sdh"
volume_id = "${element(aws_ebs_volume.riak_data.*.id, count.index)}"
instance_id = "${element(aws_instance.riak.*.id, count.index)}"
}
And then the partition script is as follows:
#!/bin/bash
if [ ! -d /data ];
then mkdir /data
fi
/sbin/mkfs -t ext4 /dev/xvdh;
while [ -e /dev/xvdh ] ; do sleep 1 ; done
mount /dev/xvdh /data
echo "/dev/xvdh /data ext4 defaults 0 2" >> /etc/fstab
Now when I do this via terraform the mkfs doesn't appear to happen and I see no obvious errors in the syslog. If I copy the script manually and just bash script.sh the mount is created and works as expected.
Has anyone got any suggestions here?
Edit: It's wort noting adding this in AWS gui under userdata also works fine.

Answer 1

You could try with remote_exec instead of user_data.
User_data relates on cloud-init which can act differently depending on images of your cloud provider.
And also i'm not sure it's a good idea to exec a script that would wait for some time before executing in the cloud-init section => this may lead to VM considering launch has failed because of a timeout (depending on your cloud provider).
Remote_exec may be better here because you will be able to wait until your /dev/xvdh is attached
See here
resource "aws_instance" "web" {
# ...
provisioner "file" {
source = "script.sh"
destination = "/tmp/script.sh"
}
provisioner "remote-exec" {
inline = [
"chmod +x /tmp/script.sh",
"/tmp/script.sh args",
]
}
}