Normally, e2undo will check the file system superblock to make sure
the undo log matches with the file system on the device. If they do not
match, e2undo will refuse to apply the undo log as a safety
mechanism. The -f option disables this safety mechanism.
Display a usage message.
Dry-run; do not actually write blocks back to the file system.
Specify the file system's offset (in bytes) from the beginning of
the device or file.
Report which block we're currently replaying.
Before overwriting a file system block, write the old contents of the
block to an undo file. This undo file can be used with e2undo(8) to
restore the old contents of the file system should something go wrong. If
the empty string is passed as the undo_file argument, the undo file will
be written to a file named e2undo-device.e2undo in the directory
specified via the E2FSPROGS_UNDO_DIR environment variable.
WARNING: The undo file cannot be used to recover from a power
or system crash.