Add 12 AI infrastructure and LLM operations skills

New skills covering hot-topic AI engineering subjects:

Local AI Infrastructure:
- vllm-server: High-throughput LLM serving with PagedAttention, tensor parallelism, quantization
- llm-inference-scaling: KEDA-based GPU autoscaling for LLM inference on Kubernetes
- rag-infrastructure: Production RAG with hybrid search, reranking, and embedding pipelines
- llm-fine-tuning: QLoRA/LoRA fine-tuning with Axolotl, DeepSpeed ZeRO-3, and DPO alignment

Infrastructure:
- gpu-server-management: NVIDIA driver setup, MIG partitioning, DCGM monitoring
- vector-database-ops: Qdrant, Weaviate, pgvector for production AI search
- llm-gateway: LiteLLM-based API gateway with rate limiting, virtual keys, fallback routing

DevOps/AI:
- llm-cost-optimization: Model right-sizing, prompt/semantic caching, batch API, break-even analysis
- llm-caching: Multi-layer exact + semantic + provider caching to cut costs 30-70%
- ai-pipeline-orchestration: Prefect/Airflow/Dagster for RAG ingestion and training workflows

Orchestration:
- model-serving-kubernetes: KServe + Triton with canary deployments and GPU autoscaling

Security:
- ai-security-hardening: Prompt injection defense, PII scrubbing, model weight verification

https://claude.ai/code/session_011MN1C4PrkCeg2Qmi7q1ZUe
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---
name: llm-fine-tuning
description: Set up infrastructure for fine-tuning LLMs with QLoRA, LoRA, and full fine-tuning using Hugging Face TRL, Axolotl, and distributed training with DeepSpeed or FSDP. Covers dataset prep, training runs, and model export.
license: MIT
metadata:
author: devops-skills
version: "1.0"
---
# LLM Fine-Tuning Infrastructure
Train and fine-tune open-source LLMs efficiently — from LoRA on a single GPU to distributed full fine-tuning across multi-node clusters.
## When to Use This Skill
Use this skill when:
- Fine-tuning an LLM on domain-specific data (legal, medical, code, support)
- Running QLoRA to fine-tune 70B models on consumer GPUs
- Setting up distributed training with DeepSpeed or FSDP
- Exporting fine-tuned adapters for production serving
- Implementing RLHF, DPO, or instruction tuning pipelines
## Prerequisites
- NVIDIA GPU(s) with 24GB+ VRAM (RTX 4090 / A100 / H100)
- CUDA 12.1+ and `nvidia-smi` working
- Python 3.10+ with `pip`
- Hugging Face account and `HF_TOKEN` for gated models
- 500GB+ disk for model weights and training data
## Quick Start: QLoRA Fine-Tuning
```bash
pip install transformers datasets trl peft bitsandbytes accelerate
python - <<'EOF'
from datasets import load_dataset
from transformers import AutoTokenizer, AutoModelForCausalLM, BitsAndBytesConfig
from peft import LoraConfig, get_peft_model
from trl import SFTTrainer, SFTConfig
import torch
model_id = "meta-llama/Llama-3.1-8B-Instruct"
# 4-bit quantization (QLoRA)
bnb_config = BitsAndBytesConfig(
load_in_4bit=True,
bnb_4bit_quant_type="nf4",
bnb_4bit_compute_dtype=torch.bfloat16,
bnb_4bit_use_double_quant=True,
)
model = AutoModelForCausalLM.from_pretrained(
model_id, quantization_config=bnb_config, device_map="auto"
)
tokenizer = AutoTokenizer.from_pretrained(model_id)
# LoRA configuration
peft_config = LoraConfig(
r=16, # rank
lora_alpha=32,
target_modules=["q_proj", "k_proj", "v_proj", "o_proj",
"gate_proj", "up_proj", "down_proj"],
lora_dropout=0.05,
bias="none",
task_type="CAUSAL_LM",
)
dataset = load_dataset("your-org/your-dataset", split="train")
trainer = SFTTrainer(
model=model,
args=SFTConfig(
output_dir="./output",
num_train_epochs=3,
per_device_train_batch_size=2,
gradient_accumulation_steps=8,
learning_rate=2e-4,
bf16=True,
logging_steps=10,
save_strategy="epoch",
report_to="wandb",
),
train_dataset=dataset,
peft_config=peft_config,
processing_class=tokenizer,
)
trainer.train()
trainer.save_model("./fine-tuned-model")
EOF
```
## Axolotl (Production Fine-Tuning Framework)
```yaml
# config.yaml — Axolotl QLoRA config for Llama 3.1
base_model: meta-llama/Llama-3.1-8B-Instruct
model_type: LlamaForCausalLM
tokenizer_type: PreTrainedTokenizerFast
load_in_4bit: true
adapter: qlora
lora_r: 32
lora_alpha: 64
lora_dropout: 0.05
lora_target_modules:
- q_proj
- k_proj
- v_proj
- o_proj
- gate_proj
- up_proj
- down_proj
datasets:
- path: your-org/your-dataset
type: alpaca # or sharegpt, chat_template, etc.
dataset_prepared_path: ./prepared-data
val_set_size: 0.05
output_dir: ./output
sequence_len: 4096
sample_packing: true # pack multiple short samples for efficiency
micro_batch_size: 2
gradient_accumulation_steps: 8
num_epochs: 3
learning_rate: 2e-4
optimizer: adamw_bnb_8bit
lr_scheduler: cosine
warmup_ratio: 0.05
bf16: true
flash_attention: true
logging_steps: 10
eval_steps: 100
save_steps: 200
wandb_project: my-fine-tune
```
```bash
# Run with Axolotl
pip install axolotl[flash-attn,deepspeed]
accelerate launch -m axolotl.cli.train config.yaml
```
## Distributed Training with DeepSpeed
```json
// deepspeed_zero3.json — ZeRO Stage 3 (split optimizer + gradients + params)
{
"zero_optimization": {
"stage": 3,
"offload_optimizer": {"device": "cpu", "pin_memory": true},
"offload_param": {"device": "cpu", "pin_memory": true},
"overlap_comm": true,
"contiguous_gradients": true,
"sub_group_size": 1e9,
"reduce_bucket_size": "auto",
"stage3_prefetch_bucket_size": "auto",
"stage3_param_persistence_threshold": "auto",
"stage3_max_live_parameters": 1e9,
"stage3_max_reuse_distance": 1e9,
"gather_16bit_weights_on_model_save": true
},
"bf16": {"enabled": true},
"gradient_clipping": 1.0,
"train_batch_size": "auto",
"train_micro_batch_size_per_gpu": "auto"
}
```
```bash
# Launch 4-GPU DeepSpeed training
deepspeed --num_gpus=4 train.py \
--deepspeed deepspeed_zero3.json \
--model_name meta-llama/Llama-3.1-70B-Instruct \
--output_dir ./output
```
## DPO / RLHF Alignment
```python
from trl import DPOTrainer, DPOConfig
from datasets import load_dataset
# Dataset format: {"prompt": ..., "chosen": ..., "rejected": ...}
dataset = load_dataset("your-org/preference-data")
trainer = DPOTrainer(
model=model,
ref_model=None, # None = implicit reference with peft
args=DPOConfig(
output_dir="./dpo-output",
beta=0.1, # KL divergence weight
num_train_epochs=1,
per_device_train_batch_size=1,
gradient_accumulation_steps=16,
learning_rate=5e-7,
bf16=True,
),
train_dataset=dataset["train"],
peft_config=peft_config,
processing_class=tokenizer,
)
trainer.train()
```
## Merging LoRA Adapters for Deployment
```python
from peft import PeftModel
from transformers import AutoModelForCausalLM
# Load base model in full precision
base_model = AutoModelForCausalLM.from_pretrained(
"meta-llama/Llama-3.1-8B-Instruct",
torch_dtype=torch.bfloat16,
device_map="cpu",
)
# Load and merge LoRA adapter
model = PeftModel.from_pretrained(base_model, "./fine-tuned-model")
merged_model = model.merge_and_unload()
# Save merged model (ready for vLLM serving)
merged_model.save_pretrained("./merged-model", safe_serialization=True)
tokenizer.save_pretrained("./merged-model")
# Push to Hugging Face Hub
merged_model.push_to_hub("your-org/your-fine-tuned-model")
```
## Kubernetes Training Job
```yaml
apiVersion: batch/v1
kind: Job
metadata:
name: llm-fine-tune
spec:
template:
spec:
restartPolicy: OnFailure
nodeSelector:
nvidia.com/gpu.product: A100-SXM4-80GB
containers:
- name: trainer
image: nvcr.io/nvidia/pytorch:24.05-py3
command: ["accelerate", "launch", "-m", "axolotl.cli.train", "/config/config.yaml"]
resources:
limits:
nvidia.com/gpu: "4"
memory: "320Gi"
requests:
nvidia.com/gpu: "4"
volumeMounts:
- name: config
mountPath: /config
- name: model-cache
mountPath: /root/.cache/huggingface
- name: output
mountPath: /output
env:
- name: HUGGING_FACE_HUB_TOKEN
valueFrom:
secretKeyRef:
name: hf-token
key: token
- name: WANDB_API_KEY
valueFrom:
secretKeyRef:
name: wandb-token
key: key
volumes:
- name: config
configMap:
name: axolotl-config
- name: model-cache
persistentVolumeClaim:
claimName: model-cache-pvc
- name: output
persistentVolumeClaim:
claimName: training-output-pvc
```
## Common Issues
| Issue | Cause | Fix |
|-------|-------|-----|
| `CUDA out of memory` | Batch too large | Reduce `micro_batch_size`; increase `gradient_accumulation_steps` |
| Training loss NaN | Learning rate too high | Lower LR to `1e-4` or `5e-5`; add warmup |
| Slow training | No Flash Attention | Install `flash-attn`; enable `flash_attention: true` |
| Poor fine-tune quality | Bad data formatting | Validate dataset format; check `sample_packing` compatibility |
| Adapter merge errors | Mixed quantization | Merge in bf16 on CPU, not in 4-bit |
## Best Practices
- Use Flash Attention 2 — it's 24× faster and uses less memory.
- Monitor training loss/eval loss via W&B or MLflow; overfit = more dropout or less data.
- Validate with a held-out eval set (510%); MMLU or custom evals for quality gates.
- Start with LoRA r=16 before increasing — higher rank = more parameters, diminishing returns.
- Use `sample_packing` in Axolotl to maximize GPU utilization on short sequences.
## Related Skills
- [vllm-server](../vllm-server/) - Serve fine-tuned models
- [gpu-server-management](../../servers/gpu-server-management/) - GPU setup
- [llm-inference-scaling](../llm-inference-scaling/) - Deploy at scale
- [ai-pipeline-orchestration](../../../devops/ai/ai-pipeline-orchestration/) - Training pipelines