System Variables

Built-in environment variables available in every Valohai execution, including execution context and agent behavior controls.

Valohai automatically sets environment variables in every execution to provide context about your job and control agent behavior.

Execution Context Variables

These variables give you information about the current execution:

# Execution paths
VH_CONFIG_DIR=/valohai/config           # Configuration files
VH_INPUTS_DIR=/valohai/inputs           # Downloaded input files
VH_OUTPUTS_DIR=/valohai/outputs         # Files to upload
VH_REPOSITORY_DIR=/valohai/repository   # Git repository code (working directory)

# Execution identifiers
VH_JOB_ID=exec-016eb6ec-50cb-0031-3f48-d556e47b1c78        # Job UUID
VH_EXECUTION_ID=016eb6ec-50cb-0031-3f48-d556e47b1c78       # Execution ID
VH_PROJECT_ID=04a37c09-dbe1-4c01-b715-0a3223c50188        # Project ID

# Pipeline context (when applicable)
VH_TASK_ID=f9c97759-513e-44a1-9666-97cf198cde80           # Task ID
VH_PIPELINE_ID=f403603b-ad11-4cc4-a90d-3118f51c8dcd       # Pipeline ID
VH_PIPELINE_NODE_ID=972834e2-23b5-429a-9f6d-80b8c4a75c8a # Pipeline node ID

💡 Use these paths to read inputs and write outputs in your code instead of hardcoding locations.

Agent Behavior Controls

Set these variables to modify how the Valohai agent handles your execution:

Cache Control

VH_NO_DATA_CACHE Ignore cached input data and re-download from source.

export VH_NO_DATA_CACHE=1  # true values: 1, yes, true

Useful when you've reused URLs but the underlying data has changed.

VH_NO_IMAGE_CACHE Force Docker image re-pull, ignoring local cache.

export VH_NO_IMAGE_CACHE=true

System Cleanup

VH_CLEAN Remove all Docker images and cached data before and after execution.

export VH_CLEAN=true

This increases execution time but ensures a clean environment.

Resource Limits

VH_CPU_LIMIT Limit CPU cores available to the job.

export VH_CPU_LIMIT=2        # Use 2 cores
export VH_CPU_LIMIT=0,2,4    # Use specific core indices

VH_MEMORY_LIMIT Set memory usage limit.

export VH_MEMORY_LIMIT=500M   # 500 megabytes
export VH_MEMORY_LIMIT=2G     # 2 gigabytes

VH_SHM_SIZE Increase shared memory directory size.

export VH_SHM_SIZE=16G       # 16 gigabytes

Useful for applications that need large shared memory (e.g., PyTorch DataLoader).

Storage Behavior

VH_TMPFS Control whether /tmp writes to memory or disk.

export VH_TMPFS=0    # false values: 0, no, false

By default, /tmp is a memory filesystem. Setting this to false writes to disk instead, which is slower but avoids out-of-memory errors for large temporary files.

Hardware Acceleration

VH_TPU Contains TPU endpoint(s) when TPUs are available.

import os
from tensorflow.python.distribute.cluster_resolver import TPUClusterResolver

# Use TPU if available
if "VH_TPU" in os.environ:
    resolver = TPUClusterResolver(tpu=os.environ["VH_TPU"].split())
    master = resolver.get_master()

This variable is only set in private environments with Google Cloud TPU enabled.