provium.toml

provium.toml is the only config file Provium reads. The default location is ./provium.toml; override with --config <path>.

The schema has two top-level keys: [provium] for runner settings, and [profiles.<name>] for per-VM-type tuples. Both are optional individually — an empty provium.toml parses cleanly but won't be useful for anything (no profiles means provium:vm(name, profile) won't find any profile to look up).

Minimum useful config #

[provium]
roots = ["tests"]

[profiles.peios]
kernel  = "/path/to/bzImage"
initrd  = "/path/to/initrd.cpio.gz"
cmdline = "console=ttyS0 quiet"

This declares one test root and one profile. provium tests/ will scan tests/ for *.test.lua, and tests can call provium:vm("name", "peios").

[provium] section #

roots #

[provium]
roots = ["tests", "vendor/upstream-tests"]

When roots is empty (or unset), provium <paths> scans whichever paths you pass on the CLI; if you also omit those, it scans the current directory.

For most projects, set roots = ["tests"] (or whichever directory contains your tests) so that:

• provium (no arg) walks the test tree.
• provium fixture build foo finds tests/foo.fixture.lua.
• Tests can require("helpers.assert_pingable") and Provium resolves it as tests/helpers/assert_pingable.lua.

cache_dir #

[provium]
cache_dir = "/var/cache/provium/fixtures"

Useful for:

• Per-machine caches on shared hosts (default is per-user, set to a system-wide path for shared CI runners).
• Fast scratch storage (point at an SSD or tmpfs for build performance).
• Large dedicated cache (point at a partition with more headroom than ~/.cache).

The directory is created on first build. If the path is unreadable / unwritable at startup, eviction silently skips and the next build attempt errors with the underlying I/O error.

cache_max_size #

[provium]
cache_max_size = "100G"

When the cache exceeds the cap, Provium sorts entries by access time and deletes oldest until total size is under the cap. Each successful restore bumps the entry's atime so popular fixtures stay hot.

[profiles.<name>] blocks #

Each [profiles.<name>] block declares one (kernel, initrd, cmdline, guest_os) tuple. Test code looks them up by name: provium:vm("v", "<name>").

You can have any number of profiles; tests pick whichever they need.

kernel #

[profiles.peios]
kernel = "/build/peios/bzImage"

Path validation (does the file actually exist?) happens at VM-boot time, not config-load time. This lets a single provium.toml be portable across machines that have different kernel layouts.

initrd #

[profiles.peios]
initrd = "/build/peios/initrd.cpio.gz"

By default, Provium injects the provium-agent binary at /sbin/provium-agent by concatenating a small overlay cpio onto your initrd at launch (the kernel unpacks concatenated gzip cpios into a single rootfs). The agent runs as PID 1, performs the standard pseudo-FS mounts, then forks: the child becomes the vsock listener, the parent execs your initrd's /init. Userspace runs as it would have on its own; the agent runs alongside as PID 2.

Three consequences:

• Your initrd doesn't need to know about Provium. A vanilla distro initramfs, a buildroot image, or a from-scratch cpio with just /init will all work.
• Your /init runs as PID 1. If your tests need PID-1 init duties (signals, child reaping), they happen in your init as before.
• The merged initrd is content-hash cached under <scratch_root>/agent-overlay-cache/<sha256>.cpio.gz. Subsequent boots of the same (initrd, overlay) pair pay nothing.

To opt out (e.g. when your initrd already bundles an agent at the path Provium would set), set inject_agent = false on the profile.

inject_agent #

[profiles.peios]
inject_agent = false

If your cmdline already pins a different rdinit=PATH, the launch errors with a clear conflict message rather than silently overriding. Either remove the conflicting rdinit=, or set inject_agent = false.

agent_overlay_path #

[profiles.peios]
agent_overlay_path = "/usr/local/share/provium/agent-overlay.cpio.gz"

When unset, Provium tries (in order): the PROVIUM_OVERLAY env var, then <provium-binary-dir>/../share/provium/agent-overlay.cpio.gz, then walks up the binary's directory tree looking for dist/agent-overlay.cpio.gz (covers in-development runs from target/). Set this field — or the env var — when none of those apply.

cmdline #

[profiles.peios]
cmdline = "console=ttyS0 quiet"

vm:boot({kernel_cmdline = "..."}) overrides the whole command line for one boot.

Provium always appends console=ttyS0 if absent. The kernel happily uses multiple console= directives, so any user-set values are preserved alongside. The reason: the QEMU command wires the serial port into Provium's console capture, so the kernel's printk needs to land there for failure diagnostics to be visible. Without console=ttyS0, PID 1's /dev/console may resolve to a device QEMU doesn't capture, and writes to stderr can fail and crash userspace.

Common additions:

• loglevel=7 — verbose kernel logging for debugging.
• nokaslr — for reproducible kernel addresses in panic dumps.
• panic=1 — panic immediately rather than hanging on unrecoverable errors.

cmdline_file #

[profiles.peios]
cmdline_file = "../peiso/out/root/boot/cmdline"
cmdline      = "loglevel=7"   # optional; appended after the file

All whitespace in the file — including newlines — is collapsed to single spaces, then the inline cmdline (if any) is appended after. Because the kernel applies last-wins semantics to most repeated parameters (init=, loglevel=, …), an inline token overrides the file's value for those.

The point is to stop the command line from drifting. If a builder bakes init=/usr/bin/protoinit into the image's cmdline and you hand-copy that into cmdline, the two silently diverge the next time the builder changes. Pointing cmdline_file at the builder's output means Provium reads the authoritative value every boot. See Dynamic profiles.

guest_os #

[profiles.peios]
guest_os = "peios"

Validated at config load time. A profile with guest_os = "linux" (or any other value) errors with profile \` has guest_os = `linux`, only `peios` is supported in v1`.

The field exists to future-proof the schema for other ports — when there's a Windows agent, this would be how a profile selects it.

build #

[profiles.peios]
build        = "peiso build manifests/peios.toml --out {out}"
kernel       = "{out}/root/boot/vmlinuz"
initrd       = "{out}/initrd.img"
cmdline_file = "{out}/root/boot/cmdline"

The literal token {out} — in build and in the path fields — expands to this profile's build-output directory (see build_out), so the command's --out and the kernel/initrd/cmdline_file Provium later reads are the same path and cannot drift.

Provium tracks no staleness: the command runs every invocation. Making rebuilds cheap when nothing changed is the builder's job, not Provium's. Skip the hook with --no-build, or run it without booting via provium prepare. Full treatment on Dynamic profiles.

build_out #

[profiles.peios]
build_out = "/tmp/provium-builds/peios"

When unset, the default base is resolved like the fixture cache — $PROVIUM_BUILD_DIR, then $XDG_CACHE_HOME/provium/builds, then ~/.cache/provium/builds, then /tmp/provium-builds — with the profile name appended. Provium creates the directory before running build but never wipes it: the build command owns its contents (so it can keep its own incremental-build caches there).

Multiple profiles #

[profiles.peios]
kernel  = "/build/peios/bzImage"
initrd  = "/build/peios/initrd.cpio.gz"
cmdline = "console=ttyS0 quiet"

[profiles.peios-debug]
kernel  = "/build/peios-debug/bzImage"
initrd  = "/build/peios-debug/initrd.cpio.gz"
cmdline = "console=ttyS0 debug loglevel=7 nokaslr"

[profiles.peios-stable]
kernel  = "/build/peios-stable/bzImage"
initrd  = "/build/peios-stable/initrd.cpio.gz"
cmdline = "console=ttyS0 quiet"

Tests pick:

provium:vm("v",        "peios")          -- production-like
provium:vm("debug-v",  "peios-debug")    -- verbose, debuggable
provium:vm("stable-v", "peios-stable")   -- pinned older kernel

Important: the fixture cache key folds in EVERY profile's kernel + initrd identifier. Adding a new profile invalidates the entire fixture cache. This is intentional: a new kernel could behave differently, so existing fixtures are no longer trustworthy.

Configuration loading #

Errors:

All three abort the run with exit code 2.

Worked example #

[provium]
roots          = ["tests", "internal-tests"]
cache_dir      = "/srv/provium-cache"
cache_max_size = "200G"

[profiles.peios]
kernel   = "/srv/peios-builds/latest/bzImage"
initrd   = "/srv/peios-builds/latest/initrd.cpio.gz"
cmdline  = "console=ttyS0 quiet panic=1"
guest_os = "peios"

[profiles.peios-mainline]
kernel   = "/srv/peios-builds/mainline/bzImage"
initrd   = "/srv/peios-builds/mainline/initrd.cpio.gz"
cmdline  = "console=ttyS0 quiet panic=1"
guest_os = "peios"

[profiles.peios-debug]
kernel   = "/srv/peios-builds/debug/bzImage"
initrd   = "/srv/peios-builds/debug/initrd.cpio.gz"
cmdline  = "console=ttyS0 debug loglevel=7 nokaslr panic=1"
guest_os = "peios"

This declares three profiles (production, mainline, debug), centralises the cache on a 200 GiB dedicated mount, and scans both tests/ and internal-tests/.

See also #

• Project structure — the broader project layout.
• VM reference — boot_opts.kernel_cmdline overrides.
• Profiles — patterns for using multiple profiles.