ImaGen/docs/setup-comfyui-mrock.md

ComfyUI on mRock — install + ops

ImaGen's flux-schnell-local backend talks to ComfyUI on mRock at http://mrock:8188 (Tailscale-internal). This document is the reproducible install path from a clean mRock state.

mRock runs Arch Linux + systemd with an NVIDIA RTX 4070 Ti SUPER (16 GB VRAM). Ollama is already a native systemd service, so ComfyUI follows the same pattern (native Python venv + systemd unit) instead of Docker — Docker on mRock has no nvidia runtime configured, and adding one is more invasive than another systemd unit.

Prerequisites on mRock

• Python via uv (already installed).
• NVIDIA driver new enough for CUDA 12.4. nvidia-smi --query-gpu=driver_version should show >= 550. Driver 595 is what mRock has today.
• ~35 GB free on /home for the model files.
• ollama.service running on port 11434 — coexistence notes below.

1. Clone ComfyUI + Python venv

mkdir -p ~/dev && cd ~/dev
git clone --depth 1 https://github.com/comfyanonymous/ComfyUI.git comfyui
cd comfyui
uv venv --python 3.12 .venv
source .venv/bin/activate.fish

# PyTorch CUDA 12.4 wheels — match the system driver
uv pip install --no-cache torch torchvision torchaudio \
    --index-url https://download.pytorch.org/whl/cu124

uv pip install --no-cache -r requirements.txt

Verify CUDA is wired up:

.venv/bin/python -c \
  "import torch; print(torch.__version__, torch.cuda.is_available(), torch.cuda.get_device_name(0))"
# expected: 2.6.0+cu124 True NVIDIA GeForce RTX 4070 Ti SUPER

2. Models — FLUX.1 schnell

The Black-Forest-Labs primary repo (black-forest-labs/FLUX.1-schnell) is gated — curl against it without an HF token returns HTTP 401. We pull the weights from ungated mirrors of the same Apache-2.0 release.

File	Where it goes	Source
flux1-schnell.safetensors (~23.8 GB, fp16)	models/unet/	Comfy-Org/flux1-schnell
ae.safetensors (~335 MB)	models/vae/	sirorable/flux-ae-vae
clip_l.safetensors (~246 MB)	models/clip/	comfyanonymous/flux_text_encoders
t5xxl_fp8_e4m3fn.safetensors (~4.9 GB)	models/clip/	comfyanonymous/flux_text_encoders

cd ~/dev/comfyui/models

curl -L -o unet/flux1-schnell.safetensors \
  https://huggingface.co/Comfy-Org/flux1-schnell/resolve/main/flux1-schnell.safetensors
curl -L -o vae/ae.safetensors \
  https://huggingface.co/sirorable/flux-ae-vae/resolve/main/ae.safetensors
curl -L -o clip/clip_l.safetensors \
  https://huggingface.co/comfyanonymous/flux_text_encoders/resolve/main/clip_l.safetensors
curl -L -o clip/t5xxl_fp8_e4m3fn.safetensors \
  https://huggingface.co/comfyanonymous/flux_text_encoders/resolve/main/t5xxl_fp8_e4m3fn.safetensors

If a new HF token is configured later (~/.cache/huggingface/token), the official black-forest-labs/FLUX.1-schnell URL is byte-identical and can be swapped in.

3. systemd unit

Drop /etc/systemd/system/comfyui.service:

[Unit]
Description=ComfyUI image generation server
Documentation=https://github.com/comfyanonymous/ComfyUI
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
User=m
Group=m
WorkingDirectory=/home/m/dev/comfyui
ExecStart=/home/m/dev/comfyui/.venv/bin/python /home/m/dev/comfyui/main.py \
    --listen 0.0.0.0 --port 8188 \
    --output-directory /home/m/dev/comfyui/output \
    --temp-directory /home/m/dev/comfyui/temp
Restart=on-failure
RestartSec=5
TimeoutStopSec=30
NoNewPrivileges=true
PrivateTmp=true
LimitNOFILE=65535

[Install]
WantedBy=multi-user.target

Then:

sudo systemctl daemon-reload
sudo systemctl enable --now comfyui.service
systemctl status comfyui.service

The service binds 0.0.0.0:8188. Tailscale's wireguard fence is the only auth — do not expose port 8188 to the public internet.

4. Health check

curl -fsS --max-time 5 http://mrock:8188/system_stats | jq '.devices[0]'
# expected: name "cuda:0 NVIDIA GeForce RTX 4070 Ti SUPER ...", vram_total ~16 GB

imagen backends (from a host with the ImaGen CLI installed) should also report flux-schnell-local: ok.

5. VRAM coexistence with Ollama

mRock has 16 GB VRAM total. Ollama parks ~8 GB resident for its current model. FLUX schnell at fp16 weights with weight_dtype=fp8_e4m3fn (the default the adapter requests) needs roughly 10–12 GB peak for a 1024×1024 generation, so concurrent Ollama + FLUX on mRock will OOM.

Two practical options:

• Stop Ollama before generating — sudo systemctl stop ollama frees the GPU, run the generation, sudo systemctl start ollama afterwards. Adequate while we don't have many concurrent users.
• Move Ollama off mRock — when ImaGen is in regular use, push Ollama to another host so the GPU is dedicated. Tracked separately.

Both decisions live with whoever operates the box; the adapter does not try to manage Ollama.

6. Smoke test (direct, without the imagen CLI)

# 1) Submit a workflow
curl -fsS --max-time 30 -X POST -H 'Content-Type: application/json' \
     -d @flux-schnell-workflow.json \
     http://mrock:8188/prompt
# returns: {"prompt_id": "...", "number": ..., "node_errors": {}}

# 2) Poll history until the prompt completes
PID=...   # from above
until curl -fsS http://mrock:8188/history/$PID | jq -e ".\"$PID\".status.completed == true" >/dev/null; do
  sleep 1
done

# 3) Pull the image
NAME=$(curl -fsS http://mrock:8188/history/$PID \
       | jq -r ".\"$PID\".outputs[\"9\"].images[0].filename")
curl -fsS "http://mrock:8188/view?filename=$NAME&type=output" -o /tmp/cat.png
file /tmp/cat.png       # PNG image data, 1024 x 1024

The full ImaGen smoke test is in usage.md once the Go adapter ships.

Troubleshooting

• vram_free < 6 GB in /system_stats: another GPU process is holding memory. Usually Ollama (sudo systemctl stop ollama).
• Workflow returns node_errors with Required input is missing for CLIPLoader: text encoder filenames don't match step 2 — check that clip_l.safetensors and t5xxl_fp8_e4m3fn.safetensors are in models/clip/, not models/text_encoders/.
• Access to model … is restricted during a model pull: the script is hitting a gated mirror. Use the ungated URLs from step 2.
• Service won't start: check journalctl -u comfyui --since '5 min ago'. Common cause is a stale pip install — re-run step 1.