Can open files be unlinked on NFS mounted volumes while applications that still have them open read/write?

Question

Does NFS allow me to unlink/delete open files like I can do with local file systems?

The reason I ask is that I'm developing something that runs on multiple servers and may access NFS as a back end. It simplifies things somewhat if I can do an unlink on a file that is open.

This is a nice feature of the linux (unix?) filesystems that you can unlink a file that is open. It simply removes the directory entry. The file is still available to a process that holds it open as long as it is open. Once closed the inode is destroyed.

Does that same functionality hold true for files opened on NFS mounts?

You may wish to rephrase (to prevent votes down), at first glance it looks like you are asking if you can delete files using NFS, which had me quite perplexed about why you would be asking such a basic question with the number of points you have. :-) — Red Tux, May 09 '11 at 05:17

score 9 · Accepted Answer · edited Mar 17 '17 at 17:53

9

The short answer is yes with caveats.

Since NFSv3 is stateless, the NFS client driver accomplishes this with something called "silly rename", where the deleted file is renamed to something like .nfsXXXXXXXXXX. This generally works, but there are a few caveats compared to a local filesystem. For instance, if the client crashes then those .nfsXXXX files will not be deleted, and you'll have to clean them up manually.

I think as of NFSv4.1 the protocol has the required features to implement delete-on-last-close without silly rename, but I don't know if any clients/server yet implement this.

edited Mar 17 '17 at 17:53

rogerdpack

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answered May 09 '11 at 05:39

janneb

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It should be noted that this works only when the file is opened on the same client which unlinks it, since NFS is stateless. – Quentin Casasnovas Mar 09 '17 at 13:28

Can open files be unlinked on NFS mounted volumes while applications that still have them open read/write?

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