How to change size of Oracle cloud block volume (OCI)

First login to Oracle cloud console and locate the instance to which the block volume is attached to. Click on the name of the instance to open the details of that instance.

Click on the Storage tab at the top. It will open the list of storage devices attached to that instance like boot volume and block volumes.

Scroll down and locate the block volume you want to change. Click on its name to show details of that instance.

On the top right you will find “Edit” button. Click on it. You will see options to change various properties of that volume.

Adjust the size of the volume and click update button on bottom right.

It may take couple of minutes to update.

After that login to the instance via SSH and follow this detailed guide.

Environment
Disk: /dev/sdb
Partition: /dev/sdb1
Filesystem: ext4
Mount Point: /blockvolume

Storage Architecture

When you increase a block volume in OCI, only the disk layer becomes larger. The partition and filesystem do not automatically expand.

Example Scenario

You increase the OCI volume from 100 GB to 200 GB.

The additional 100 GB exists but cannot be used until the partition and filesystem are expanded.

Step 1 – Verify Current State

lsblk df -Th /blockvolume 

sudo fdisk -l /dev/sdb

These commands help determine the size of the disk, partition and filesystem. They establish a baseline before making any changes.

Step 2 – Verify Device Access

sudo dd iflag=direct if=/dev/sdb of=/dev/null count=1

This verifies Linux can communicate directly with the underlying storage device.

Step 3 – Rescan the Disk

echo 1 | sudo tee /sys/class/block/sdb/device/rescan

This triggers a kernel-level rescan so Linux refreshes device metadata and detects the new size without a reboot.

Step 4 – Confirm New Disk Size

lsblk sudo fdisk -l /dev/sdb

You should now see the disk reporting its new size while the partition still shows the old size.

Step 5 – Expand the Partition

sudo growpart /dev/sdb 1

This modifies the partition table so partition 1 consumes all available free space on the disk.

Before: |======== sdb1 100G ========|—— free ——-|

After: |================ sdb1 200G =================|

Step 6 – Verify Partition Growth

lsblk

The partition size should now match the disk size.

Step 7 – Expand the ext4 Filesystem

sudo resize2fs /dev/sdb1

The partition is larger, but the filesystem still uses the old size. resize2fs updates ext4 metadata structures and enables use of all newly available blocks.

Before: Partition 200G Filesystem 99G

After: Partition 200G Filesystem 199G

Step 8 – Verify Available Space

df -Th /blockvolume

This confirms applications can access the new storage.

Step 9 – Validate Filesystem Metadata

sudo tune2fs -l /dev/sdb1

tune2fs displays ext4 internals such as:

• Filesystem UUID
• Block count
• Block size
• Filesystem state
• Reserved block count
• Filesystem features

sudo tune2fs -l /dev/sdb1 | grep -E "Block count|Block size|Filesystem state"

Golden Rule:
Every expansion must occur in order:

OCI Volume → Linux Disk → Partition → Filesystem → Verification.

If any layer is skipped, the additional space is not usable.