}

    /**
     * Downloads a specific backup file by ID.
     * Supports various backup formats including system properties, bulk data, and NDJSON logs.
     *
     * @param id the backup file ID to download
     * @return stream response containing the backup file data
     */
    // GET /api/admin/backup/file/{id}
    @Execute
    public StreamResponse get$file(final String id) {

		<Property name="log.file.basedir" value="${sys:fess.log.path:-target/logs}" />
		<Property name="backup.date.suffix" value="_%d{yyyyMMdd}" />
		<Property name="backup.max.history" value="10" />
		<Property name="backup.max.age" value="90" />
		<Property name="backup.audit.max.age" value="360" />
		<Property name="backup.searchlog.max.age" value="90" />
		<Property name="audit.log.pattern" value="%msg%n" />

      locale: {
        format: "YYYY-MM-DD HH:mm"
      }
    })
    .on("apply.daterangepicker", function(ev, picker) {
      $(this).val(
        picker.startDate.format("YYYY-MM-DD HH:mm") +
          " - " +
          picker.endDate.format("YYYY-MM-DD HH:mm")
      );
    });

  // Time picker
  $("input.form-control.time").timepicker({
    showInputs: false
  });

  // tooltips
  $(function() {

// UnsealETag unseals the etag using the provided object key.
// It does not try to decrypt the ETag if len(etag) == 16
// because such ETags indicate that the S3 client hasn't sent
// an ETag = MD5(object) and the backend has picked an ETag value.
func (key ObjectKey) UnsealETag(etag []byte) ([]byte, error) {
	if !IsETagSealed(etag) {
		return etag, nil
	}
	mac := hmac.New(sha256.New, key[:])
	mac.Write([]byte("SSE-etag"))

```

### Importing Configuration

**Via Admin UI**:
1. **System > Backup > Upload**
2. Select `fess*.json` file
3. Click **Import**

**Via API**:
```bash
curl -X POST "http://localhost:8080/api/admin/backup/upload" \
  -u admin:admin \
  -F "file=@fess-config-backup.json"
```

### System Properties

Critical system settings in `system.properties`:

```properties

 *
 * @author Pete Gillin
 * @since 20.0
 */
@GwtIncompatible
@J2ktIncompatible
@NullUnmarked
enum QuantilesAlgorithm {

  /**
   * Sorts the dataset, and picks values from it. When computing multiple quantiles, we sort once
   * and pick multiple values.
   */
  SORTING {

    @Override
    double singleQuantile(int index, int scale, double[] dataset) {
      Arrays.sort(dataset);

 *
 * @author Pete Gillin
 * @since 20.0
 */
@GwtIncompatible
@J2ktIncompatible
@NullUnmarked
enum QuantilesAlgorithm {

  /**
   * Sorts the dataset, and picks values from it. When computing multiple quantiles, we sort once
   * and pick multiple values.
   */
  SORTING {

    @Override
    double singleQuantile(int index, int scale, double[] dataset) {
      Arrays.sort(dataset);

		<Property name="log.file.basedir" value="${sys:fess.log.path:-target/logs}" />
		<Property name="backup.date.suffix" value="_%d{yyyyMMdd}" />
		<Property name="backup.max.history" value="10" />
	</Properties>

	<Appenders>
		<RollingFile name="AppFile" fileName="${log.file.basedir}/${domain.name}.log"
			filePattern="${log.file.basedir}/${domain.name}${backup.date.suffix}-%i.log.gz">

		<Property name="log.file.basedir" value="${sys:fess.log.path:-target/logs}" />
		<Property name="backup.date.suffix" value="_%d{yyyyMMdd}" />
		<Property name="backup.max.history" value="10" />
	</Properties>

	<Appenders>
		<RollingFile name="AppFile" fileName="${log.file.basedir}/${domain.name}.log"
			filePattern="${log.file.basedir}/${domain.name}${backup.date.suffix}-%i.log.gz">

    <jsp:include page="/WEB-INF/view/common/admin/sidebar.jsp">
        <jsp:param name="menuCategoryType" value="log"/>
        <jsp:param name="menuType" value="backup"/>
    </jsp:include>
    <main class="content-wrapper">
        <div class="content-header">
            <div class="container-fluid">
                <div class="row mb-2">
                    <div class="col-sm-6">