In addition to storing virtual disks on NFS datastores, you can also use NFS as a central repository for ISO images, virtual machine templates, and so on.
To use NFS as a shared repository, you create a directory on the NFS server and then mount it as a datastore on all hosts. If you use the datastore for ISO images, you can connect the virtual machine's CD-ROM device to an ISO file on the datastore and install a guest operating system from the ISO file.
If the underlying NFS volume, on which the files are stored, is read-only, make sure that the volume is exported as a read-only share by the NFS server, or configure it as a read-only datastore on the ESXi host. Otherwise, the host considers the datastore to be read-write and might not be able to open the files.