mgr/dashboard: NFS Ganesha Object Gateway exports should default to read-only and warn if RW is requested
The Ceph Dashboard includes a GUI for Ganesha management. The configuration UI allows users to select Object Gateway backed exports with different access modes (RO, RW, etc.).
As documented in http://docs.ceph.com/docs/master/radosgw/nfs/ , the NFS Object Gateway has a number of limitations which will seriously affect applications writing to the share:
The RGW NFS interface supports most operations on files and directories, with the following restrictions: Links, including symlinks, are not supported NFS ACLs are not supported Unix user and group ownership and permissions are supported Directories may not be moved/renamed files may be moved between directories Only full, sequential write i/o is supported i.e., write operations are constrained to be uploads many typical i/o operations such as editing files in place will necessarily fail as they perform non-sequential stores some file utilities apparently writing sequentially (e.g., some versions of GNU tar) may fail due to infrequent non-sequential stores When mounting via NFS, sequential application i/o can generally be constrained to be written sequentially to the NFS server via a synchronous mount option (e.g. -osync in Linux) NFS clients which cannot mount synchronously (e.g., MS Windows) will not be able to upload files
Because of these limitations, the Dashboard should configure Object Gateway Ganesha exports to be read-only by default. If write is selected, a warning should be shown with a link to the excerpt above.