firecracker-microvm/firecracker · error · SnapshotError

File too short to contain CRC

Error message

File too short to contain CRC

What it means

Error "File too short to contain CRC" thrown in firecracker-microvm/firecracker.

Source

Thrown at src/vmm/src/snapshot/mod.rs:99

/// Assumes the raw bytes stream read from the given [`Read`] instance is a snapshot file,
/// and returns the version of it.
pub fn get_format_version<R: Read>(reader: &mut R) -> Result<Version, SnapshotError> {
    // Check size limit before reading the full file to prevent DOS attacks
    let mut buf = Vec::new();
    let bytes_read = reader
        .take((SNAPSHOT_DESERIALIZATION_BYTES_LIMIT + 1) as u64)
        .read_to_end(&mut buf)?;

    if bytes_read > SNAPSHOT_DESERIALIZATION_BYTES_LIMIT {
        return Err(SnapshotError::SizeLimitExceeded(
            SNAPSHOT_DESERIALIZATION_BYTES_LIMIT,
        ));
    }

    // The last 8 bytes are the CRC, so we need to separate them for deserialization
    if buf.len() < 8 {
        return Err(SnapshotError::Io(std::io::Error::new(
            std::io::ErrorKind::UnexpectedEof,
            "File too short to contain CRC",
        )));
    }

    let (data_buf, _crc_buf) = buf.split_at(buf.len() - 8);

    // Since bitcode requires exact type matching, we need to try deserializing
    // as the specific snapshot type we know about. In practice, all snapshots
    // in Firecracker use MicrovmState as the data type.
    use crate::persist::MicrovmState;

    match bitcode::deserialize::<Snapshot<MicrovmState>>(data_buf) {
        Ok(snapshot) => Ok(snapshot.header.version),
        Err(e) => {
            // If deserialization fails, it could be due to:
            // 1. The snapshot was created with bincode (older versions)
            // 2. The MicrovmState structure has changed and is incompatible

View on GitHub (pinned to 0a745def42)

Solutions

1. Regenerate the snapshot file; the current file is truncated or corrupted and lacks its CRC trailer.
2. Verify the snapshot file transfer completed and its size matches expectations before loading.

When it happens

Trigger: Thrown at src/vmm/src/snapshot/mod.rs:99 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of firecracker-microvm/firecracker@0a745def42 (2026-08-19). Data as JSON: /api/errors/b32a14cf49747fe4. Report an issue: GitHub.