Expanding EC2 Root EBS Volume Without Downtime

Ubuntu 24.04.4 LTS (ARM), root volume on EBS, managed via Terraform.

Disk usage was already near full:

root@anantafatur:~/anantafatur-tfworkload# df -h
Filesystem       Size  Used Avail Use% Mounted on
/dev/root         23G   22G  1.2G  95% /

Current disk layout:

root@anantafatur:~/anantafatur-tfworkload# lsblk
NAME         MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0          7:0    0 24.2M  1 loop /snap/amazon-ssm-agent/13008
loop1          7:1    0   69M  1 loop /snap/core22/2412
loop2          7:2    0 42.6M  1 loop /snap/snapd/26869
nvme0n1      259:0    0   24G  0 disk
├─nvme0n1p1  259:1    0   23G  0 part /
├─nvme0n1p15 259:2    0   99M  0 part /boot/efi
└─nvme0n1p16 259:3    0  923M  0 part /boot

Updated only the root volume size in Terraform:

root_block_device {
  volume_size = 26
}

Terraform showed in-place modification:

root@anantafatur:~/anantafatur-tfworkload# terraform plan

Terraform will perform the following actions:

  # aws_instance.main will be updated in-place
  ~ resource "aws_instance" "main" {

      ~ root_block_device {
          ~ volume_size = 24 -> 26
        }
    }

Plan: 0 to add, 1 to change, 0 to destroy.

Applied:

root@anantafatur:~/anantafatur-tfworkload# terraform apply

After apply, EBS volume size increased immediately, but partition size was still unchanged:

root@anantafatur:~/anantafatur-tfworkload# lsblk
NAME         MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0          7:0    0 24.2M  1 loop /snap/amazon-ssm-agent/13008
loop1          7:1    0   69M  1 loop /snap/core22/2412
loop2          7:2    0 42.6M  1 loop /snap/snapd/26869
nvme0n1      259:0    0   26G  0 disk
├─nvme0n1p1  259:1    0   23G  0 part /
├─nvme0n1p15 259:2    0   99M  0 part /boot/efi
└─nvme0n1p16 259:3    0  923M  0 part /boot

Expanded partition online:

root@anantafatur:~/anantafatur-tfworkload# sudo growpart /dev/nvme0n1 1

CHANGED: partition=1 start=2099200 old: size=48232415 end=50331614 new: size=52426719 end=54525918

Then resized ext4 filesystem:

root@anantafatur:~/anantafatur-tfworkload# sudo resize2fs /dev/nvme0n1p1

resize2fs 1.47.0 (5-Feb-2023)
Filesystem at /dev/nvme0n1p1 is mounted on /; on-line resizing required
old_desc_blocks = 3, new_desc_blocks = 4
The filesystem on /dev/nvme0n1p1 is now 6553339 (4k) blocks long.

Final result:

root@anantafatur:~/anantafatur-tfworkload# df -h
Filesystem       Size  Used Avail Use% Mounted on
/dev/root         25G   22G  3.1G  88% /

root@anantafatur:~/anantafatur-tfworkload# lsblk
NAME         MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0          7:0    0 24.2M  1 loop /snap/amazon-ssm-agent/13008
loop1          7:1    0   69M  1 loop /snap/core22/2412
loop2          7:2    0 42.6M  1 loop /snap/snapd/26869
nvme0n1      259:0    0   26G  0 disk
├─nvme0n1p1  259:1    0   25G  0 part /
├─nvme0n1p15 259:2    0   99M  0 part /boot/efi
└─nvme0n1p16 259:3    0  923M  0 part /boot

Notes:

• AWS volume state was still optimizing while resizing filesystem. No issue observed.
• Nitro instances expose EBS as NVMe (/dev/nvme0n1).
• growpart came from cloud-guest-utils.
• No reboot needed during the process.