YAML Configuration Reference¶

Slicer uses a YAML configuration file to define host groups, networking, storage, and API settings. Generate one with slicer new or let slicer auto create one for you.

Generate a config file¶

slicer new vm > config.yaml

The argument (vm) becomes the host group name. slicer new detects the host architecture and selects the correct image automatically.

Full example¶

config:
  host_groups:
  - name: vm
    storage: image
    storage_size: 25G
    count: 1
    vcpu: 2
    ram_gb: 4
    network:
      bridge: brvm0
      tap_prefix: vmtap
      gateway: 192.168.137.1/24

  github_user: alexellis

  image: "ghcr.io/openfaasltd/slicer-systemd:6.1.90-x86_64-latest"

  hypervisor: firecracker

  api:
    port: 8080
    bind_address: "127.0.0.1"

Host group fields¶

Each entry in host_groups defines a group of identically-configured VMs.

Field	Type	Default	Description
`name`	string		Host group name, used to derive bridge and tap names
`count`	int	`1`	Number of VMs to create. Set to `0` to launch VMs via API instead
`vcpu`	int	`2`	vCPUs per VM
`ram_gb`	int	`4`	RAM in GiB per VM
`ram_mb`	int		RAM in MiB (alternative to `ram_gb`)
`ram_bytes`	int		RAM in bytes (alternative to `ram_gb`)
`storage`	string	`devmapper`	Storage backend: `image`, `devmapper`, or `zfs`
`storage_size`	string		Disk size, e.g. `25G` or `512M`. Required for `image` storage
`persistent`	bool	`false`	Keep root filesystem after VM shutdown
`userdata`	string		Inline cloud-init user data
`userdata_file`	string		Path to a cloud-init user data file
`dns_servers`	list	`["8.8.8.8", "1.1.1.1"]`	DNS servers for VMs
`gpu_count`	int	`0`	Number of GPUs to pass through

Only one of ram_gb, ram_mb, or ram_bytes can be specified.

Networking¶

See the networking reference for detailed configuration.

Bridge mode (default)¶

VMs get routable IPs on a Linux bridge and are reachable via SSH from the host.

Field	Type	Description
`network.bridge`	string	Bridge interface name, e.g. `brvm0`
`network.tap_prefix`	string	Prefix for TAP interfaces (max 14 chars)
`network.gateway`	string	Gateway in CIDR notation, e.g. `192.168.137.1/24`
`network.addresses`	list	Optional static IPs. Auto-assigned from the gateway range if empty

Isolated mode¶

VMs have no inbound access from the host network. Use slicer vm exec, slicer vm forward, or slicer vm shell to interact with them.

Field	Type	Description
`network.mode`	string	Set to `isolated`
`network.drop`	list	CIDRs to block
`network.allow`	list	CIDRs to allow (whitelist mode if no `drop` rules)

Storage¶

Backend	Notes
`image`	Disk image cloned from the rootfs. Simplest to set up. Requires `storage_size`. See the walkthrough.
`devmapper`	Device mapper snapshots. Fastest cloning. See devmapper docs.
`zfs`	ZFS volumes. See ZFS docs.

SSH access¶

Field	Type	Description
`github_user`	string	GitHub username - public SSH keys are fetched from the profile
`ssh_keys`	list	SSH public keys as strings

At least one of github_user or ssh_keys is needed for SSH access. Keys can also be managed via the SSH keys API.

API¶

The API can bind to a TCP address or a unix socket.

With TCP, requests are authenticated with a bearer token written to /var/lib/slicer/auth/token. With a unix socket, the OS filesystem permissions control access so no token is needed.

Field	Type	Default	Description
`api.port`	int	`8080`	TCP port
`api.bind_address`	string	`127.0.0.1`	TCP address or unix socket path (e.g. `./slicer.sock`)
`api.auth.enabled`	bool	`true`	Enable bearer token authentication

See the API reference for endpoint documentation.

Other fields¶

Field	Type	Default	Description
`image`	string		OCI image reference for the root filesystem
`kernel_image`	string		OCI image containing a kernel (optional)
`kernel_file`	string		Path to a kernel binary (optional, extracted from rootfs if not set)
`hypervisor`	string	`firecracker`	`firecracker` or `cloud-hypervisor`
`graceful_shutdown`	bool	`true`	Send ACPI shutdown before killing VMs
`pci`	map		PCI device passthrough. See VFIO docs