Left Over .nfs (dot nfs) Files

I recently had a situation where an NFS file system was constantly filling with these strange .nfs files. If a file is removed while a running process still has it open, that file is renamed as .nfs and a long hex string. The symptoms are fairly easy to reproduce:

# touch testfile
# tail -f testfile
From another session:
# rm testfile
# ls -la
-rw-r--r-- 1 root    root    0 Jul 23 13:31 .nfs000000000033468f00000003

To find the offending process run an lsof .nfsxxxxx and kill it, however, because NFS mounts can be spread across several clients, it may take a bit of searching to find the right one. Once the process is terminated the client should automatically clean the file.

I should also point out that in my testing, both the process and the delete operation have to come from the same client. NFS doesn't enforce any file locking which means if a file is deleted from another machine the system doesn't know to rename it first. It is left up to the application to sort this out. Most do nothing about it which means you will get a stale NFS handle message on the source process.