Linux NFS client and FreeBSD server strangeness

Mike Tancsa mike at
Thu Apr 5 15:49:10 UTC 2018

On 4/4/2018 4:23 PM, Kaya Saman wrote:
> If I recall correctly the "sync" option is default. Though it might be
> different depending on the Linux distro in use?
> I use this: vers=3,defaults,auto,tcp,rsize=8192,wsize=8192

Thanks. For ubuntu 16, it looks like the default is async. It would be
nice if all of these defaults were exposed to view.  Also the rw buffers
are higher than the above at 131072. I too am using 9000 for the MTU.

After doing

mount.nfs -o intr,noatime,vers=3 -v

the options that come up are

mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying prog 100005 vers 3 prot UDP port 944

kind of odd in that they dont display all of them

mount | grep nfs

192.168.xx.yy:/zbackup1/virtbox4b/backup on /backup type nfs

The sync/async

  The sync mount option
       The NFS client treats the sync mount option differently than some
other file systems (refer to mount(8) for a description of  the
       generic  sync  and  async  mount options).  If neither sync nor
async is specified (or if the async option is specified), the NFS
       client delays sending application writes to the server until any
of these events occur:

              Memory pressure forces reclamation of system memory resources.

              An application flushes file data explicitly with sync(2),
msync(2), or fsync(3).

              An application closes a file with close(2).

              The file is locked/unlocked via fcntl(2).


Mike Tancsa, tel +1 519 651 3400 x203
Sentex Communications, mike at
Providing Internet services since 1994
Cambridge, Ontario Canada

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