Answer by Thomas for setting up secure tmpfs in fstab

The first field is the storage backend you want to mount. In case of tmpfs, there is none storage backend.

From man fstab

The first field (fs_spec).
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For filesystems with no storage, any string can be used, and will show up in df(1) output, for example.Typical usage is proc for procfs; mem, none, or tmpfs for tmpfs.
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