How to Resize a Disk on Google Cloud Linux VM

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After resizing a Google Cloud disk in the console, your Linux VM still shows the old storage size. This is expected. Google Cloud only expands the raw block device. The partition and filesystem inside the VM still need extending. This guide walks through all three steps of the Google Cloud disk resize process on Linux without stopping or restarting the instance.

Google Cloud disk resize Linux VM persistent disk storage
Google Cloud disk resize in the console is just the first step. The partition and filesystem still need extending inside the VM.

Step 1: Resize the Google Cloud Persistent Disk

Resize the Google Cloud disk in the console by going to Compute Engine → Disks, selecting the disk, and clicking Edit. Enter the new size and save. Or use the gcloud CLI:

gcloud compute disks resize DISK_NAME --size=200GB --zone=us-central1-a

The full reference is on the Google Cloud persistent disk resize documentation page. Note that Google Cloud only allows increasing disk size. You cannot shrink a Google Cloud disk once it has been resized.

Also useful is the gcloud compute disks resize CLI reference for scripting disk resizes across multiple instances.

Step 2: Confirm the New Size on the Linux VM

Google Cloud Linux disk resize gcloud command terminal growpart
After a Google Cloud disk resize, lsblk shows the new block device size while the partition still reflects the old size.

SSH into the VM and check that the kernel sees the updated Google Cloud disk size:

lsblk

The disk device (usually /dev/sda on GCP VMs) should show the new size, but the partition below it still shows the old value. Also note current usage:

df -h

If the disk still shows the old size, run a rescan:

echo 1 > /sys/class/block/sda/device/rescan

Google Cloud Disk Resize: Extend the Partition

Install growpart if it is not already present:

# Ubuntu / Debian
apt install cloud-guest-utils -y

# RHEL / AlmaLinux / Rocky Linux
dnf install cloud-utils-growpart -y

Extend the partition to use all the new Google Cloud disk space:

growpart /dev/sda 1

Check with lsblk that the partition now matches the disk. If your VM uses LVM (common in RHEL marketplace images), also run:

pvresize /dev/sda1
lvextend -l +100%FREE /dev/vg0/root

See our LVM disk management guide for full details on extending LVM volumes after resizing the underlying disk.

Step 3: Extend the Filesystem

Google Cloud disk resize filesystem xfs ext4 Linux resize2fs
After extending the partition, grow the filesystem to claim the new space. No reboot needed on Google Cloud Linux VMs.

Check the filesystem type and resize it:

# Check first
df -Th

# ext4 - Debian and Ubuntu images
resize2fs /dev/sda1

# XFS - RHEL and Rocky Linux images
xfs_growfs /

# Confirm
df -h /

The same steps apply to data disks. If your data disk is mounted at /data on /dev/sdb, run growpart /dev/sdb 1 then resize the filesystem at that mount point. No unmounting is needed.

Conclusion

A complete Google Cloud disk resize on Linux needs three steps: resize in GCP, extend the partition with growpart, and grow the filesystem. The whole process runs without stopping the VM and takes under five minutes. For a broader view of Linux disk management, see our Linux server hardening checklist for storage configuration best practices.

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