Repair a damaged filesystem

Filesystems can be corrupted due to unexpected power loss, system crashes and unsafe removal of the drive. After such an incident it is recommended to repair or at least check the filesystem to prevent future data loss.

Sometimes a repair is required in order to mount or modify a filesystem. Even if a check does not report any damage the filesystem might still be marked as ‘dirty’ internally and require a repair.

Check if a filesystem is damaged

  1. Open Disks from the desktop.

  2. Select the disk containing the filesystem in question from the list of storage devices on the left. If there is more than one volume on the disk, select the volume which contains the filesystem.

  3. In the toolbar underneath the Volumes section, click the menu button. Then click Check Filesystem….

  4. Depending on how much data is stored in the filesystem a check may take longer time. Confirm to start the action in the dialog that pops up.

    The action will not modify the filesystem but will unmount it if needed. Be patient while the filesystem is checked.

  5. After completion you will be notified whether the filesystem is damaged. Note that in some cases even if the filesystem is undamaged it still may need to be repaired to reset an internal ‘dirty’ marker.

Possible data loss when repairing

If the filesystem structure is damaged it can affect the files stored in it. In some cases these files can not be brought into a valid form again and will be deleted or moved to a special directory. It is normally the lost+found folder in the top level directory of the filesystem where these recovered file parts can be found.

If the data is too valuable to be lost during this process, you are advised to back it up by saving an image of the volume before repairing.

This image can be then processed with forensic analysis tools like sleuthkit to further recover missing files and data parts which were not restored during the repair, and also previously removed files.

Repair a filesystem

  1. Open Disks from the desktop.

  2. Select the disk containing the filesystem in question from the list of storage devices on the left. If there is more than one volume on the disk, select the volume which contains the filesystem.

  3. In the toolbar underneath the Volumes section, click the menu button. Then click Repair Filesystem….

  4. Depending on how much data is stored in the filesystem a repair may take longer time. Confirm to start the action in the dialog that pops up.

    The action will unmount the filesystem if needed. The repair action tries to bring the filesystem into a consistent state and moves files which were damaged in a special folder. Be patient while the filesystem is repaired.

  5. After completion you will be notified whether the filesystem could be successfully repaired. In case of success it can be used again in the normal way.

    If the filesystem could not be repaired, back it up by saving an image of the volume to be able to retrieve important files later. This can be done by mounting the image read-only or using forensic analysis tools like sleuthkit.

    To make use of the volume again it has to be formatted with a new filesystem. All data will be discarded.