kopia/kopia · error

windows GetCapacity

Error message

windows GetCapacity

What it means

On Windows, GetCapacity converts fs.RootPath to a UTF-16 pointer via windows.UTF16PtrFromString and calls windows.GetDiskFreeSpaceEx; failure of either is wrapped as "windows GetCapacity". This reports that Windows could not resolve the path or query free disk space for the volume containing the storage root.

Solutions

1. Verify the drive letter / UNC path in RootPath is valid and accessible (run dir <path> in cmd)
2. Check disk connectivity and remap disconnected network drives
3. Normalize the path to a Windows-style absolute path before configuring storage
4. Ensure the path string contains only characters valid for windows.UTF16PtrFromString (no embedded NULs, no wildcards)

Example fix

// before
st, err := fs.New(ctx, fs Options{Path: "/mnt/data"})
// after
st, err := fs.New(ctx, fs Options{Path: `D:\Backups\kopia`}) // valid Windows path
if err != nil {
    log.Fatal(err)
}

func validWindowsPath(p string) error {
    if p == "" || strings.ContainsAny(p, "*?\x00") {
        return fmt.Errorf("invalid Windows path: %q", p)
    }
    if _, err := os.Stat(p); err != nil {
        return err
    }
    return nil
}

cap, err := st.GetCapacity(ctx)
if err != nil && strings.Contains(err.Error(), "windows GetCapacity") {
    // check drive mapping / path validity before retrying
}

When it happens

Trigger: Calling GetCapacity when fs.RootPath is an invalid Windows path (illegal characters like : * ?, empty string), points to a non-existent/unmapped drive letter, or the volume is unavailable (disconnected network drive).

Common situations: Path using forward slashes or UNC path misformatted; USB/network drive disconnected; drive letter changed after the storage was opened; path exceeding MAX_PATH limitations.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

• can't get local fs entry
• can't re-create top-level directory
• entry not found
• entry not found : parent is not a directory
• error resolving config file path

AI-assisted analysis of kopia/kopia@82495e54b5 (2026-09-07). Data as JSON: /api/errors/db6a52aa1f3fbe00. Report an issue: GitHub.

Appendix: source

Thrown at repo/blob/filesystem/filesystem_storage_capacity_windows.go:19

//go:build windows

package filesystem

import (
	"context"

	"github.com/pkg/errors"
	"golang.org/x/sys/windows"

	"github.com/kopia/kopia/repo/blob"
)

func (fs *fsStorage) GetCapacity(_ context.Context) (blob.Capacity, error) {
	var c blob.Capacity

	pathPtr, err := windows.UTF16PtrFromString(fs.RootPath)
	if err != nil {
		return blob.Capacity{}, errors.Wrap(err, "windows GetCapacity")
	}

	err = windows.GetDiskFreeSpaceEx(pathPtr, nil, &c.SizeB, &c.FreeB)
	if err != nil {
		return blob.Capacity{}, errors.Wrap(err, "windows GetCapacity")
	}

	return c, nil
}

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