Mount point with different owner/group permissions?

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http://serverfault.com – We have a media server where all of our audio, etc. is served out of. A few different servers mount a certain directly on the media server. I noticed though, that depending on which server I'm looking at the files from, the owner/group is different. For example, on the media server, all of the directories are owned by user media. On one of our web servers, all of the directories appear to be owned by the application user. This makes it easy for an application to read and write data to the media server, without having to give 777 permissions to the directory. How is this possible? I hope this (HowTos)