What are EFS files starting with .nfs?

Question

I'm trying to debug a file-based PHP CMS that is continuously trying to write a file, but failing. I saw the following:

```
-rw-r--r-- 1 webapp webapp  87717 Aug  2 09:01 response.cache
-rw-r--r-- 1 webapp webapp 167700 Aug  2 09:57 .nfs3bb62bc5d551a49f0000000c
```

There's the old file `response.cache` and a file starting with ".nfs" that contains updated content. My guess is that EFS is in the process of writing the file while other instances of the PHP script try to read/write it. In any case, it appears to be a part of the issue.

What is that file?

Jack Hemion · Accepted Answer

Hi dodov,

In Linux running over NFS, .nfs files are created when a file opened on a client is deleted from the file system while still opened. The client renames the file to a fairly long string like you're seeing in order to discourage other clients or processes from using the file.

Usually you can find out what process is causing using the lsof command, in this case:

```
lsof .nfs3bb62bc5d551a49f0000000c
```
This will output the process that is working with the file, and if necessary, you can then kill said process.

What are EFS files starting with .nfs?

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