Fine-Tune FLUX.1 for Custom Image Generation

Common issues

The Hardware platform column shows where an issue is most relevant. "All hardware platforms" applies to every platform listed in this playbook.

Symptom	Hardware platform	Cause	Fix
Cannot access gated repo for URL	All hardware platforms	Hugging Face model access restricted or token invalid	Regenerate your Hugging Face token; request access to the gated model in a browser; export a valid `HF_TOKEN` before `download.sh`
"permission denied" when running Docker	All hardware platforms	User not in the `docker` group	Run `sudo usermod -aG docker $USER && newgrp docker`
Container fails to start with GPU error	All hardware platforms	NVIDIA Container Toolkit not configured	Configure the NVIDIA Container Toolkit for Docker and confirm `nvidia-smi` works in a GPU container
ComfyUI unreachable on port 8188	All hardware platforms	Container not running or port blocked	Confirm `launch_comfyui.sh` is running; open `http://localhost:8188` or `http://<HARDWARE_IP>:8188`
Training OOM / memory pressure during train or generate	All hardware platforms	Other GPU jobs, residual cache, or workload exceeds available memory	Stop other GPU processes; bring down ComfyUI before training; flush buffer cache (see note); reduce resolution or batch-related settings if needed
Memory pressure within capacity	DGX Spark	UMA buffer cache not released	See UMA note below

NOTE

Unified memory (UMA). On hardware platforms with unified memory, GPU and CPU share memory dynamically. Some applications have not yet been updated for UMA, so you may hit memory issues even within capacity. If that happens, manually flush the buffer cache:

Bash

sudo sh -c 'sync; echo 3 > /proc/sys/vm/drop_caches'

For latest known issues, see the documentation linked under Resources for your hardware platform.