Unsupported Characters for Backblaze B2 (File Names Must not Contain DELETE)

Issue Description

The backup plan fails with the following error message: “File names must not contain DELETE”

The error is returned by BackBlaze storage, once unsupported symbols in filenames are detected.

Filenames can be pretty much any UTF-8 string up to 1024 bytes long, with the following limitations:

  • No character codes below 32 are allowed
  • Backslashes are not allowed
  • DEL characters (127) are not allowed
  • File names cannot start with "/", end with "/", or contain "//".

To learn more, refer to the Files article at backblaze.com

Resolve the Issue

To avoid this error, remove all unsupported symbols in filenames of your backup source.

Mind that filenames can contain control characters which are invisible in file manager software:

but can be seen in log files:

Once you are done with renaming files, run the backup plan again.


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