Yes, OCI fully supports Bring Your Own Image (BYOI), allowing you to upload and run custom operating system images that you’ve built on-premises or in other clouds.

As of 2026, the process is streamlined to support both modern "cloud-native" images and legacy workloads. Here is how it works:

1. Supported Formats & Sizes

You can upload images in the most common virtualization formats:

• QCOW2: The standard for QEMU/KVM.

• VMDK: The standard for VMware environments.

• OCI: A specialized format used when moving custom images between OCI tenancies or regions.

• Size Limit: You can import images up to 400 GB.

2. Launch Modes (How the Hardware "Talks" to Your OS)

When you import an image, you choose a Launch Mode based on how modern your OS is:

• Native Mode: The fastest performance. Used for images that already have OCI’s specialized drivers (VirtIO).

• Paravirtualized Mode: The recommended mode for most modern Linux (kernel 3.4+) and Windows images. It offers a balance of high performance and broad compatibility.

• Emulated Mode: The "compatibility" mode. It mimics older hardware (like E1000 network cards). It’s slower but allows you to run legacy operating systems that don't support modern cloud drivers.

3. The "Bare Metal" Challenge

While VMs are flexible, booting a custom image on Bare Metal requires extra steps. Because OCI Bare Metal servers boot over the network (iSCSI), your custom image must:

• Include iSCSI boot support in the initramfs.

• Have Cloud-Init (version 20.3 or later) installed to handle OCI metadata and SSH keys.

• Support specific kernel parameters to reach the boot volume over the network.

4. How to Upload (The Workflow)

The process involves a simple three-step "Handshake":

1. Upload to Object Storage: First, you upload your .qcow2 or .vmdk file to an OCI Object Storage bucket.

2. Import as Custom Image: In the OCI Console, go to Compute > Custom Images > Import Image. You point OCI to the file in your bucket.

3. Launch Instance: Once the status turns "Available," you can click Create Instance directly from that image.

5. Automated Image Building (DevOps)

For teams that need to update images frequently, OCI supports automated "Image Pipelines":

• HashiCorp Packer: OCI has an official Packer builder that can automatically spin up a base image, install your software, run security hardening, and save it as a new Custom Image.

• RHEL Image Builder: If you use Red Hat, you can push customized RHEL images directly from your on-premises console into your OCI tenancy.

Comparison: Custom vs. Platform Images

Pro-Tip: The "Generalization" Step

Before uploading a Windows image, you must run Sysprep to "generalize" it. This removes computer-specific info (like the SID and drivers) so that when OCI clones the image to a new server, it doesn't run into naming or hardware conflicts.