PyTorch: CondaVerificationError During PyTorch and CUDA Toolkit Installation

Verified FixPython 3.10+PyTorch 2.2+, Conda 24.1+Silo: pytorch

Quick Fix / Solution Rapide

This error occurs when Python packages downloaded by Conda fail checksum or signature verification due to interrupted downloads. Clear the Conda cache with conda clean --all and reinstall PyTorch.

Root Cause Analysis

This error occurs when the Conda package manager downloads PyTorch binaries, CUDA toolkits, or dependent libraries (such as cudatoolkit, pytorch-cuda, or torchaudio), but fails during safety verification before unpacking.

Root Cause 1: Interrupted or Incomplete Package Downloads

PyTorch CUDA packages are massive (often exceeding 2GB to 4GB per package). If a network timeout, proxy disconnection, or disk I/O stall interrupts the download, the cached .conda or .tar.bz2 archive in ~/miniconda3/pkgs/ becomes corrupted. When Conda computes the SHA-256 hash against the channel metadata, the verification fails with CondaVerificationError.

Root Cause 2: Antivirus or Security Scanner Locking Package Archives

On Windows and corporate enterprise environments, real-time endpoint security scanners (Windows Defender, CrowdStrike, SentinelOne) inspect and lock temporary downloaded archive files while Conda attempts to extract them.

Root Cause 3: Stale or Inconsistent Channel Metadata

Mixing packages from different channels (pytorch, nvidia, conda-forge, defaults) can cause metadata conflicts where version checksums don't match the repository index.

Root Cause 4: Insufficient Disk Space in Temporary Directories

If the partition hosting the temporary directory (/tmp or %TEMP%) runs out of storage during decompression, Conda aborts with partial file corruption.

Reproduction Code (MCVE)

Example: Bug Reproduction

# Simulating Conda package verification checksum failure
class MockCondaPackageVerifier:
    def verify_package(self, expected_sha256: str, actual_sha256: str):
        if expected_sha256 != actual_sha256:
            raise OSError(
                "CondaVerificationError: The package for pytorch located at "
                "C:\Users\user\miniconda3\pkgs\pytorch-2.2.0-py3.10_cuda12.1.tar.bz2 "
                "failed verification (checksum mismatch). Package file is corrupted."
            )

verifier = MockCondaPackageVerifier()
verifier.verify_package(
    expected_sha256="e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
    actual_sha256="corrupted_partial_download_hash_value"
)

Solution 1: Purge Conda Cache and Reinstall PyTorch

Run conda clean --all to delete incomplete downloads and cached tarballs, then rerun the official PyTorch installation command.

Example: Recommended Solution

# Solution 1: Terminal commands to resolve Conda verification failure
cleanup_commands = [
    "conda clean --all --yes",
    "conda install pytorch torchvision torchaudio pytorch-cuda=12.1 -c pytorch -c nvidia --yes"
]

print("Recommended cleanup sequence:")
for cmd in cleanup_commands:
    print(f"  $ {cmd}")

assert len(cleanup_commands) == 2

Solution 2: Use pip as an Alternative Wheel Installer

If Conda channels continue experiencing network verification issues, install pre-built PyTorch wheels via pip.

Example: Alternative Solution

# Solution 2: Alternative pip install command using official PyTorch index
pip_cmd = "pip install torch torchvision torchaudio --index-url https://download.pytorch.org/whl/cu121"

print("Alternative installation command:")
print(f"  $ {pip_cmd}")
assert "download.pytorch.org" in pip_cmd

Avoid manually deleting files inside the pkgs directory while Conda is running, as this can corrupt the Conda environment registry database (conda-meta). Always use the official conda clean -a -y command.

Note de reproductibilité : Cette erreur dépend de la stabilité de la connexion réseau, des politiques de pare-feu d'entreprise, de la configuration du cache Conda et de l'espace disque disponible.

Contrast CondaVerificationError with ResolvePackageNotFound: ResolvePackageNotFound means no package matching your constraints exists on the channel; CondaVerificationError means the package exists and was downloaded, but the downloaded file is corrupted or tampered.

Previous Next