формат fstab и параметры для файловых систем nfs (fstab format and options for the nfs file systems)
THE REMOUNT OPTION
Generic mount options such as rw and sync can be modified on NFS
mount points using the remount option. See mount(8) for more
information on generic mount options.
With few exceptions, NFS-specific options are not able to be
modified during a remount. The underlying transport or NFS
version cannot be changed by a remount, for example.
Performing a remount on an NFS file system mounted with the noac
option may have unintended consequences. The noac option is a
combination of the generic option sync, and the NFS-specific
option actimeo=0.
Unmounting after a remount
For mount points that use NFS versions 2 or 3, the NFS umount
subcommand depends on knowing the original set of mount options
used to perform the MNT operation. These options are stored on
disk by the NFS mount subcommand, and can be erased by a remount.
To ensure that the saved mount options are not erased during a
remount, specify either the local mount directory, or the server
hostname and export pathname, but not both, during a remount.
For example,
mount -o remount,ro /mnt
merges the mount option ro with the mount options already saved
on disk for the NFS server mounted at /mnt.
