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After executing xdiskusage without arguments, the initial default view will be the list of partitions: By double-clicking in some partition you will get the list of the biggest directories (arranged by size) and the space that each one is using: (notice that free space is shown as another directory) You can double-click in any other directory to explore it. Right-clicking shows a menu with some options like hide, unhide, go in, go out, etc.