Solved or not solved Sudoku can be saved into file with extension sdk.
Free Sudoku for Linux (KDE/Qt version) generator has 3 levels of difficulties. You may print created Sudoku grid or play on computer screen. No installation is required, simply download sudoku.rar file, unpack it and play. Solved or not solved Sudokus may be saved into file with extension sdk. Later saved files may be loaded in 9x9 Sudoku grid.