VictoriaMetrics/VictoriaMetrics · error

cannot open %q for preallocation: %w

Error message

cannot open %q for preallocation: %w

What it means

Fires in the Linux preallocateFile when os.OpenFile cannot open the target path (O_WRONLY|O_CREATE) prior to fallocate. Input at fault is the part file path; wrapped error is an open failure — missing parent directory, permissions, or a read-only filesystem.

Source

Thrown at lib/backup/fslocal/prealloc_linux.go:17

package fslocal

import (
	"fmt"
	"os"
	"syscall"
)

const canPreallocate = true

func preallocateFile(path string, size int64) error {
	if size <= 0 {
		return nil
	}
	f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE, 0600)
	if err != nil {
		return fmt.Errorf("cannot open %q for preallocation: %w", path, err)
	}
	err = syscall.Fallocate(int(f.Fd()), 0, 0, size)
	if err1 := f.Close(); err1 != nil && err == nil {
		err = err1
	}
	if err != nil {
		return fmt.Errorf("cannot fallocate %d bytes for %q: %w", size, path, err)
	}
	return nil
}

View on GitHub (pinned to 5079fb58f1)

Solutions

1. Ensure the parent directory exists and is writable
2. Check filesystem is mounted read-write
3. Disable preallocation (SkipPreallocation) as a workaround on unsupported filesystems

When it happens

Trigger: Thrown at lib/backup/fslocal/prealloc_linux.go:17 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of VictoriaMetrics/VictoriaMetrics@5079fb58f1 (2026-09-03). Data as JSON: /api/errors/d460df4a15cd0288. Report an issue: GitHub.