Partitions And Mounting

Technical Background

Cloud volumes in cloud environments such as Hetzner are virtual block devices that can be dynamically attached to a virtual machine. They can be automatically mounted, partitioned, and formatted with different file systems. In Linux, storage devices are represented as /dev/sdX, and partitions as /dev/sdXn. Mounting is the process of attaching a file system (ext4, xfs, etc.) to a directory tree so that files become accessible. Persistent mounts are typically defined in /etc/fstab.

In this exercise, you extend a Terraform configuration with an attached volume, manually explore partitions using fdisk, create multiple file systems, and configure persistent mounts via /etc/fstab. A known bug in Hetzner’s volume automount feature requires triggering udevadm to detect the device after creation.

Solution

Prerequisits

Create a main.tf, outputs.tf, /tpl/* variables.tf, network.tf,providers.tf and secrets.auto.tfvars like in 14 Solving Known Host Quirk.

Add an additional volume using Terraform

1. Create a file volumes.tf that contains:

resource "hcloud_volume" "volume01" {
  name      = "volume1"
  size      = 10
  server_id = hcloud_server.web.id
  automount = true
  format    = "xfs"
}

1. Output the volume device by adding this to outputs.tf:

output "volume_device" {
    value = hcloud_volume.volume01.linux_device
}

1. Apply configuration:

terraform init
terraform apply

1. Reboot the server :

sudo reboot

1. Validate the mount after reboot:

df -h

Unmounting the Volume

1. Change into the mount directory:

cd /mnt/HC_Volume_...

1. Try unmounting:

sudo umount /mnt/HC_Volume_...

1. Change to / and unmount again:

cd /
sudo umount /mnt/HC_Volume_...

Partitioning a Volume

1. Identify the device:

lsblk

1. Create two partitions:

sudo fdisk /dev/sdb

1. Check results:

sudo fdisk -l /dev/sdb

Create File System

1. Create ext4 on the first partition:

sudo mkfs -t ext4 /dev/sdb1

1. Create xfs on the second partition:

sudo mkfs -t xfs /dev/sdb2

Mount Manually

1. Create mount points:

sudo mkdir /disk1 /disk2

1. Mount partitions:

sudo mount /dev/sdb1 /disk1

1. Use blkid to get the UUID of the second partition:

sudo blkid /dev/sdb2

1. Test with files:

sudo touch /disk1/testfile
ls /disk1

1. Unmount both and show content:

sudo umount /disk1 /disk2
ls -l /disk1

Persistent Mounting for Partition

1. Get UUID of second partition:

sudo blkid /dev/sdb2

1. Edit /etc/fstab:

/dev/sdb1   /disk1  ext4  defaults,nofail  0  2
UUID=<uuid> /disk2  xfs   defaults,nofail  0  2

1. Test:

sudo mount -a

1. Reboot:

sudo reboot

1. Validate:

df -h

Related Links

Terraform Hetzner Docs

Terraform Outputs

Hcloud Terraform Automount Bug

Hcloud Volumes

Linux CLI