System I know has /etc/exports (redacted address range; NFSv4, Linux 5.8.3):
/usr/users 192.168.68.0/255.255.255.128(rw,root_squash,sync,no_subtree_check)
which is mounted on client machines (to offer remote home directories). But on the same server that exports these, users are allowed to log in locally and access their local home directory directly via /usr/users; which is its own ext3 filesystem (mount options are only rw,relatime).
Doesn't that mean the NFS server can not know when a user modifies a file locally, so that remote and local files diverge? Or is consistency guaranteed by some fanotify-based mechanism or similar?
So, to conclude:
- I want to know how mixed local/NFS access makes different guarantees than NFS-only access
- especially w.r.t. server-side and client-side caching
- especially w.r.t. whether we can tell at which point an NFS read would be consistent after a local write, and vice versa
- I want to know whether a file being changed locally gets propagated at all to the clients (for data consistency, but also for
select/pollreasons)- especially w.r.t. how that is done/implemented and what requirements on the local file system/access need to be fulfilled
