Terraform: Mount volume

Question

According to documentation, using terraform, I'm able to create a droplet on digital ocean:

resource "digitalocean_volume" "foobar" {
  region      = "nyc1"
  name        = "baz"
  size        = 100
  description = "an example volume"
}

So, I'm also able to add a volume to it:

resource "digitalocean_droplet" "foobar" {
  name       = "baz"
  size       = "1gb"
  image      = "coreos-stable"
  region     = "nyc1"
  volume_ids = ["${digitalocean_volume.foobar.id}"]
}

I'd like to know how to mount this on a desired location. I need to mount it automatically. I mean, when droplet is up I need to the volume is mounted. I was thinking about using chef...

Any ideas?

score 8 · Accepted Answer · edited Mar 10 '22 at 11:49

To mount the volume automatically, you can use user_data via cloud init to run a script as follow:

This is how your digitalocean_droplet resources should reflect:

resource "digitalocean_droplet" "foobar" {
  name       = "baz"
  size       = "1gb"
  image      = "coreos-stable"
  region     = "nyc1"
  volume_ids = ["${digitalocean_volume.foobar.id}"]
   # user data
  user_data = "${data.template_cloudinit_config.cloudinit-example.rendered}"
}

Then your cloud.init file that contains the cloudinit_config should be as bellow. It will reference the shell script in ${TERRAFORM_HOME}/scripts/disk.sh that would mount your volume automatically:

provider "cloudinit" {}


data "template_file" "shell-script" {
  template = "${file("scripts/disk.sh")}"
  
}
data "template_cloudinit_config" "cloudinit-example" {

  gzip = false
  base64_encode = false

  part {
    content_type = "text/x-shellscript"
    content      = "${data.template_file.shell-script.rendered}"
  }

}

The shell script to mount the volume automatically on startup is in ${TERRAFORM_HOME}/scripts/disk.sh

It will first check if a file system exist. If true it wouldn't format the disk if not it will

#!/bin/bash


DEVICE_FS=`blkid -o value -s TYPE ${DEVICE}`
if [ "`echo -n $DEVICE_FS`" == "" ] ; then
        mkfs.ext4 ${DEVICE}
fi
mkdir -p /data
echo '${DEVICE} /data ext4 defaults 0 0' >> /etc/fstab
mount /data

I hope this helps

A provider called `cloudinit` doesn't exist in Terraform (or it's plugins). Additionally, where is `DEVICE` set at or coming from? — Dids, May 30 '18 at 08:09
I understand now, in the data.template_file.shell-script you can have set vars, there you can define what DEVICE is set to and it will be replaced by terraform when applying the file — Rumbles, Mar 13 '19 at 09:00
I wrote this for aws but just notice that the commands are slightly different for ubuntu 18 https://stackoverflow.com/a/63126594/8723007 — valem, Jul 28 '20 at 03:29

score 7 · Answer 2 · edited Mar 10 '21 at 19:10

7

Mounting the volume needs to be done from the guest OS itself using mount, fstab, etc.

The digital ocean docs cover this here.

Using Chef you could use resource_mount to mount it in an automated fashion.

The device name will be /dev/disk/by-id/scsi-0DO_Volume_YOUR_VOLUME_NAME. So, using the example from the Terraform docs, it would be /dev/disk/by-id/scsi-0DO_Volume_baz.

edited Mar 10 '21 at 19:10

James

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answered May 19 '17 at 13:08

c3st7n

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I need to mount it automatically with droplet. – Jordi May 19 '17 at 13:16
Are you using any config management like puppet, chef or ansible to confugure the droplet after boot? If not, you could simply run a mount command from your user-data. – c3st7n May 19 '17 at 13:18
Yes! Nevertheless, I'm not quite to understand where the volume is created as a device (I mean `/dev/???`). Could you take a look on [this documentation](https://www.terraform.io/docs/providers/do/r/volume.html). Are you able to figure out where the volume is located? – Jordi May 19 '17 at 13:44
If you read the documentation I listed it shows that the device name will be `/dev/disk/by-id/scsi-0DO_Volume_YOUR_VOLUME_NAME`. So using the example from the terraform docs it would be `/dev/disk/by-id/scsi-0DO_Volume_baz`. – c3st7n May 19 '17 at 13:51

Terraform: Mount volume

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