GardenLinux

GardenLinux is the Linux distribution used as the operating system on CobaltCore hypervisor nodes. It is a Debian-based, cloud-optimized OS designed specifically for running Kubernetes and virtualization workloads in production.

Why GardenLinux?

• Minimal attack surface - stripped to only what is needed; no package manager or shell in production images
• Immutable by default - OS is read-only; changes are applied by replacing the image, not modifying the running system
• Kernel tuned for KVM - includes the patches and configuration needed for high-performance libvirt and KVM workloads
• Automated updates - Gardener manages GardenLinux upgrades on hypervisor nodes with zero-downtime rolling updates

Role in CobaltCore

GardenLinux is the OS layer that the KVM hypervisor agents run on. The Hypervisor Operator interacts with GardenLinux through systemd unit management and the node agent - no SSH or manual shell access is needed for routine operations.

The hypervisor stack runs on top of GardenLinux:

VMs
└── libvirt / KVM
    └── Containerized agents (Nova, Neutron, HA, Node)
        └── GardenLinux
            └── Bare metal node (managed by IronCore)

Further reading

• GardenLinux documentation
• GardenLinux GitHub