How ONTAP treats read-only bits
The read-only bit is set on a file-by-file basis to reflect whether a file is writable (disabled) or read-only (enabled).
SMB clients that use Windows can set a per-file read-only bit. NFS clients do not set a per-file read-only bit because NFS clients do not have any protocol operations that use a per-file read-only bit.
ONTAP can set a read-only bit on a file when an SMB client that uses Windows creates that file. ONTAP can also set a read-only bit when a file is shared between NFS clients and SMB clients. Some software, when used by NFS clients and SMB clients, requires the read-only bit to be enabled.
For ONTAP to keep the appropriate read and write permissions on a file shared between NFS clients and SMB clients, it treats the read-only bit according to the following rules:
NFS treats any file with the read-only bit enabled as if it has no write permission bits enabled.
If an NFS client disables all write permission bits and at least one of those bits had previously been enabled, ONTAP enables the read-only bit for that file.
If an NFS client enables any write permission bit, ONTAP disables the read-only bit for that file.
If the read-only bit for a file is enabled and an NFS client attempts to discover permissions for the file, the permission bits for the file are not sent to the NFS client; instead, ONTAP sends the permission bits to the NFS client with the write permission bits masked.
If the read-only bit for a file is enabled and an SMB client disables the read-only bit, ONTAP enables the owner’s write permission bit for the file.
Files with the read-only bit enabled are writable only by root.
Changes to file permissions take effect immediately on SMB clients, but might not take effect immediately on NFS clients if the NFS client enables attribute caching.