openmediavault/openmediavault · error · OMV\Exception

Failed to get list of unused devices.

Error message

Failed to get list of unused devices.

What it means

Thrown by the unused-devices RPC when the storage device enumeration call (filtered to non-read-only devices) returns false instead of an array, meaning the underlying enumeration of storage devices failed entirely rather than merely returning an empty list. The boolean-false sentinel marks an internal enumeration error (e.g. command failures while probing disks).

Solutions

1. Run the probing commands manually (lsblk, blkid) as the omv user to find which command fails, and repair it (reinstall util-linux/blkid, fix device nodes).
2. Check dmesg/journalctl for storage-layer errors (I/O errors, hot-unplug during scan) and rescan.
3. If running in a container, expose /sys, /proc and /dev block devices properly to the openmediavault-engined process.
4. Patch the RPC to return a partial/empty list or a structured error instead of a bare OMV\Exception when enumeration fails, so the UI can distinguish 'no unused devices' from 'scan failed'.

exec('lsblk --all --json 2>&1', $out, $rc);
if (0 !== $rc) {
    die("storage probing broken, fix lsblk/blkid before calling getUnusedDevices\n");
}
$this->rpc('FileSystemMgmt', 'getUnusedDevices', []);

function storageEnumerationWorks(): bool {
    exec('lsblk -d -n -o NAME 2>/dev/null', $out, $rc);
    return 0 === $rc;
}

try {
    $devs = $this->rpc('FileSystemMgmt', 'getUnusedDevices', []);
} catch (\OMV\Exception $e) {
    if (str_contains($e->getMessage(), 'Failed to get list of unused devices')) {
        sleep(2); // transient device churn: retry after a short backoff
        $devs = $this->rpc('FileSystemMgmt', 'getUnusedDevices', []);
    } else {
        throw $e;
    }
}

When it happens

Trigger: Calling rpc.filesystemmgmt.getUnusedDevices when \OMV\System\Storage\...::getDevices-style enumeration with the isReadOnly filter returns false — typically when blkid/lsblk/sysfs probing fails at the OS level.

Common situations: Broken /proc or /sys visibility in containers, missing or failing block-device tools, devices disappearing mid-scan (USB hot-unplug), or permissions/seccomp issues preventing the engined process from reading device information.

Understand the failure class

Background: EmptyResultError / "no results found": when an API or scraper succeeds but returns zero rows — this error's family across 9 libraries.

Related errors

• Failed to get list of storage devices
• Failed to start session.
• Failed to write session data.
• Failed to get list of hard disks and hardware RAID devices.
• No file system backend set for

AI-assisted analysis of openmediavault/openmediavault@dce610eb66 (2026-09-15). Data as JSON: /api/errors/4a568fd048746cec. Report an issue: GitHub.

Appendix: source

Thrown at deb/openmediavault/usr/share/openmediavault/engined/rpc/filesystemmgmt.inc:597

     *   devicefile, size and description.
     * @throw \OMV\Exception
     */
    public function getCandidates($params, $context)
    {
        // Validate the RPC caller context.
        $this->validateMethodContext($context, [
            "role" => OMV_ROLE_ADMINISTRATOR
        ]);
        // Get a list of all potential usable devices (excluding read-only devices).
        $devs = \OMV\System\Storage\StorageDevice::enumerateUnusedObjects(
            OMV_STORAGE_DEVICE_KIND_DEFAULT,
            \OMV\LogicalOperator::ALL,
            function (\OMV\System\Storage\StorageDeviceInterface $sd): bool {
                return !$sd->isReadOnly();
            }
        );
        if (false === $devs) {
            throw new \OMV\Exception("Failed to get list of unused devices.");
        }
        // Get a list of all detected file systems.
        $filesystems = \OMV\System\Filesystem\Filesystem::getFilesystems();
        // Get the list of device files that are occupied by a file system.
        $usedDevs = [];
        foreach ($filesystems as $filesystemk => $filesystemv) {
            $usedDevs[] = $filesystemv->getParentDeviceFile();
            // Check if the file system uses multiple devices, e.g.
            // a BTRFS RAID, and add them.
            if ($filesystemv->hasMultipleDevices()) {
                $usedDevs = array_merge(
                    $filesystemv->getDeviceFiles(),
                    $usedDevs
                );
            }
        }
        $usedDevs = array_values(array_filter($usedDevs, "strlen"));
        // Prepare the result list.

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