Applies to

• Fedora CoreOS 44.x
• Hyper‑V virtual machines
• Default installation (single disk, XFS root filesystem, no custom Ignition storage config)

Overview

Fedora CoreOS automatically expands the root partition only on first boot. If you later increase the VM’s virtual disk size (for example, from 10 GB to 25 GB), the root partition and filesystem will not resize automatically. Manual steps are required.

This article describes the supported method to expand the root partition and filesystem.

Prerequisites

• The VM disk size has already been increased in Hyper‑V
• Root or sudo access on the Fedora CoreOS VM
• Recommended: VM snapshot or backup before proceeding

Procedure

Step 1: Verify Disk and Partition Sizes

Confirm the OS sees the new disk size and identify the root partition (usually /dev/sda4).

lsblk
df -hT /sysroot

Expected:

• The disk (e.g. /dev/sda) shows the new size (25 GB)
• The root partition (/dev/sda4) still shows the old size (~10 GB)

If the disk still shows the old size, rescan it:

echo 1 | sudo tee /sys/block/sda/device/rescan

Step 2: Expand the Root Partition

Extend partition 4 to fill the newly available disk space:

sudo growpart /dev/sda 4

Verify the change:

lsblk

The root partition (/dev/sda4) should now reflect the larger size.

Step 3: Remount /sysroot as Read‑Write

Fedora CoreOS mounts /sysroot as read‑only by default. To safely modify it, use a temporary mount namespace:

sudo unshare --mount
mount -o remount,rw /sysroot

Step 4: Grow the XFS Filesystem

Expand the XFS filesystem to use the new partition size:

xfs_growfs /sysroot

Exit the mount namespace:

exit

Step 5: Confirm the Result

Verify the filesystem now uses the full disk size:

df -h /sysroot
lsblk

Important Notes

• Fedora CoreOS uses XFS for the root filesystem; always use xfs_growfs (not resize2fs).
• Ignition and automatic resizing apply only during first boot.
• This procedure is online and does not require reinstallation.
• The system remains compliant with Fedora CoreOS’s immutable design.

Outcome

The root partition and filesystem now fully utilize the expanded virtual disk capacity.