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Instance Per Tenant

For stronger isolation, run a separate Slicer daemon per tenant. Each gets its own UNIX socket, its own network range, and its own VM namespace. Tenant A cannot see, manage, or reach tenant B's VMs.

┌───────────────────────────────────────────────────────┐
│  Your Application                                     │
│                                                       │
│  Tenant A request ──► /run/slicer/a3cf.sock           │
│  Tenant B request ──► /run/slicer/e7d1.sock           │
└───────────┬───────────────────────────┬───────────────┘
            ▼                           ▼
┌─────────────────────┐   ┌─────────────────────┐
│ Slicer (a3cf)       │   │ Slicer (e7d1)       │
│ 169.254.100.0/22    │   │ 169.254.104.0/22    │
│                     │   │                     │
│ ┌────────┐┌────────┐│   │ ┌────────┐┌────────┐│
│ │ a3cf-1 ││ a3cf-2 ││   │ │ e7d1-1 ││ e7d1-2 ││
│ └────────┘└────────┘│   │ └────────┘└────────┘│
└─────────────────────┘   └─────────────────────┘

When to use this

Use a separate instance per tenant when:

  • You need API-level isolation - one tenant's requests cannot access another's VMs
  • You need network isolation between tenants
  • You want independent failure domains - one tenant's daemon crashing does not affect others
  • Compliance or security requirements demand full separation

Configuration

Generate a config per tenant with isolated networking, a UNIX socket, and a non-overlapping IP range. Use isolated mode networking so VMs from different tenants cannot communicate.

Tenant A:

slicer new a3cf \
  --net=isolated \
  --isolated-range 169.254.100.0/22 \
  --socket /run/slicer/a3cf.sock \
  --count=0 \
  --graceful-shutdown=false \
  --drop 192.168.1.0/24 \
  > tenant-a.yaml

This produces:

config:
  host_groups:
    - name: a3cf
      storage: image
      storage_size: 25G
      count: 0
      vcpu: 2
      ram_gb: 4
      network:
        mode: "isolated"
        range: "169.254.100.0/22"
        drop: ["192.168.1.0/24"]
        allow: ["0.0.0.0/0"]
  image: "ghcr.io/openfaasltd/slicer-systemd:6.1.90-x86_64-latest"
  hypervisor: firecracker
  graceful_shutdown: false
  api:
    bind_address: "/run/slicer/a3cf.sock"

Tenant B:

slicer new e7d1 \
  --net=isolated \
  --isolated-range 169.254.104.0/22 \
  --socket /run/slicer/e7d1.sock \
  --count=0 \
  --graceful-shutdown=false \
  --drop 192.168.1.0/24 \
  > tenant-b.yaml

config:
  host_groups:
    - name: e7d1
      storage: image
      storage_size: 25G
      count: 0
      vcpu: 2
      ram_gb: 4
      network:
        mode: "isolated"
        range: "169.254.104.0/22"
        drop: ["192.168.1.0/24"]
        allow: ["0.0.0.0/0"]
  image: "ghcr.io/openfaasltd/slicer-systemd:6.1.90-x86_64-latest"
  hypervisor: firecracker
  graceful_shutdown: false
  api:
    bind_address: "/run/slicer/e7d1.sock"

Each /22 range provides 256 usable VM slots. Use non-overlapping ranges when running multiple daemons on the same host (e.g. 169.254.100.0/22, 169.254.104.0/22, 169.254.108.0/22).

In isolated mode, each VM gets its own network namespace. VMs cannot communicate with each other, with the host, or with the LAN. The drop list blocks specific CIDRs. Auth is disabled by default for UNIX sockets since access is controlled by filesystem permissions.

Start each daemon

Start each daemon in its own terminal or tmux window:

sudo slicer up tenant-a.yaml

sudo slicer up tenant-b.yaml

Each daemon manages its own VMs. Your application routes requests to the correct socket based on which tenant is making the request.

For production, run each daemon as a systemd service - one unit per tenant. See running in the background for setup.

API isolation

Each daemon has its own VM namespace. Listing nodes on tenant A's socket returns only tenant A's VMs:

TOKEN=$(sudo cat /var/lib/slicer/auth/token)

# Tenant A: create a VM
sudo curl -sf --unix-socket /run/slicer/a3cf.sock \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -X POST http://localhost/hostgroup/a3cf/nodes \
  -d '{"tags":["user=alice","job=123"]}'

# Tenant B: create a VM
sudo curl -sf --unix-socket /run/slicer/e7d1.sock \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -X POST http://localhost/hostgroup/e7d1/nodes \
  -d '{"tags":["user=bob","job=456"]}'

# Tenant A sees only its own VMs
sudo curl -sf --unix-socket /run/slicer/a3cf.sock \
  -H "Authorization: Bearer $TOKEN" http://localhost/nodes

[{"hostname":"a3cf-1","hostgroup":"a3cf","ip":"169.254.100.2",
  "tags":["user=alice","job=123"],"status":"Running"}]

Tenant A cannot manage, exec into, or copy files to tenant B's VMs through its socket.

See also