NFS problem

Chuck Swiger cswiger at
Wed May 2 17:25:39 UTC 2007

John Clark wrote:
> I am copying a 'disk image' to an NFS mounted volume.
> I'm using:
> dd if=/dev/ad0 of=Disk.img
> After dd completes the number of blocks indicated is what the raw disk 
> device should be. However, when I look at the NFS mounted image, the file size is 
> anything but the 80 GB size it should be.

How big is it?  Is the data complete/intact up to the point when it stopped?

Can you create enough local space on a second drive (or do this by individial 
partitions instead) to create the image locally, and then copy the file at 
once via NFS?  It'd be nice to see whether that worked OK.

> I have not used NFS very much in the last few years, but I don't recall 
> such data loss as being something to worry about. The NFS transactions, while using 
> UDP, may be 'lost', but there was some form of retry and eventually the file data 
> would be received, or ultimately the NFS client would emit some error message.

One would hope so, yes.  Is it possible that doing an fsync or system-wide 
sync would help get the blocks written out...?

Does using tar or dump/rmt work any better?


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