Failed to create "/var/alchemy/Phraseanet/www/thumbnails/aa/28": mkdir(): Permission denied

[Mike2100]

Dear,
Through windows 11, I access wsl unbuntu.
Each time I upload a file, error happens. Like below.

An exception has been thrown during the rendering of a template ("Failed to create "/var/alchemy/Phraseanet/www/thumbnails/aa/28": mkdir(): Permission denied.").
Failed to create "/var/alchemy/Phraseanet/www/thumbnails/aa/28": mkdir(): Permission denied.