When you increase a Linode Block Storage volume’s size in the Cloud Manager, the added capacity doesn’t automatically appear inside your Linux system. You need to let the kernel detect the change and then expand the filesystem so it can use the new space.

Previously I create article by umount firts, this one no need to umount because a new more modern Linux kernel version.

• How to Resize a Linode Volume Disk on Debian 12 Without Data Loss

The following steps apply to Debian 12 and assume you’re using an ext4 filesystem on a device such as /dev/sdc, mounted at a generic directory like /mnt/data.

1. Check if the kernel detects the new size

After resizing the volume in Linode Cloud Manager, log in to your instance and verify whether the kernel already sees the larger capacity:

If the output shows the new size (for example sdc 80G ext4 /mnt/data), you can continue. If it still shows the old size, rescan the device manually:

2. Expand the filesystem (ext4)

Modern Linux kernels allow online resizing of ext4 filesystems, so you can grow it while it’s mounted:

This command safely extends the ext4 filesystem to fill all available space on the disk.

3. Verify the new capacity

Once resizing completes, check that the mounted filesystem now reflects the full size:

You should see output similar to:

Notes

No downtime is required for ext4 on modern Debian kernels. If resizing fails or you prefer to validate the filesystem offline, unmount it first:

For XFS filesystems, use sudo xfs_growfs /mnt/data instead of resize2fs.

Final check

To ensure consistent mounts after reboot, use stable device IDs rather than /dev/sdX names:

Then update your /etc/fstab entry to use the /dev/disk/by-id/ path for that volume.

Resizing a Linode Block Storage volume requires two key steps, expanding the volume in Cloud Manager and then growing the filesystem inside your Debian 12 instance.

With resize2fs, you can do it live, safely, and without unmounting the disk.