container instance
test instance
A test that declares image — the OCI image booted in a vmlab micro-VM. Linux, ready in seconds.
A test block declaring image runs in a vmlab container: the OCI image you name, booted inside a micro-VM. It is Linux-only and ready in seconds, which makes it the default choice for anything that is really just a userland — file, package and config resources.
Unlike an unprivileged container runtime, it holds a full capability set and its own kernel, so resources that need NET_ADMIN or a real kernel (nftables, ufw, firewalld) work here too.
| Field | Value |
|---|---|
| declared with | image = "debian:12" |
| guest OS | Linux, always |
| requires | an image with a shell; no host container runtime |
| parallelism | --container-jobs N (default min(cpu, 8)) |
| memory | 256MiB by default; raise with memory = "4GiB" on the test |
Two measured gotchas: dnf5 loads its repositories fine in a Fedora container but then wedges for minutes on the transaction itself (use a VM for real dnf installs), and a test needing a live init system, a reboot or a Windows guest must use a VM.