question about feature to overwrite free disk space

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I understand that the feature to overwrite free disk space is implemented by writing a large file until all available disk space is used up, and then deleting that file ...

The question I have is about how this may affect stability of a running system -- what if another process tries to write a file larger than the available disk space before the overwrite free disk space process is completed?

Yes, that is basically the way BleachBit 1.3 cleans free disk space. The wiping process takes a while (minutes or hours), and only during a brief time (maybe seconds) is the disk completely full.

If another process is actively writing a file during the brief time when the disk is full, that process will encounter a write error. The severity of the error depends on the process. For example, if your web browser fails writing an image to the cache, not much is lost. If your word processor fails to write an important document, you can probably try again later (assuming you do not exit the word processor). But you can imagine a worse scenario.

For this reason, it's best not to wipe the disk space of a system that is actively in use.

If you often find a need for wiping the disk space, consider instead encrypting the partition.

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Andrew, lead developer