一个linux系统中的某个文件夹无法删除，使用ls -al查看有1个.nfsxxxx的文件无法删除。

使用lsof +D /filepath/，查看到文件被一个进程一直占用。

再使用ps -aux | grep pid，查看是一个java进程一直在占用，杀掉这个进程后，文件夹正常删除。

　　What is this .nfsxxxxxxxxxxxxxx file and why can’t I remove it?

　　Under unix, if you remove a file that a currently running process still has open, the file isn’t really removed. Once the process closes the file, the OS then removes the file handle and frees up the disk blocks. This process is complicated slightly when the file that is 　open and removed is on an NFS mounted filesystem. Since the process that has the file open is running on one machine (such as a workstation in your office or lab) and the files are on the file server, there has to be some way for the two machines to communicate 　　information about this file. The way NFS does this is with the .nfsNNNN files. If you try to remove one of these file, and the file is still open, it will just reappear with a different number. So, in order to remove the file completely you must kill the process that has it open.
　　If you want to know what process has this file open, you can use ‘lsof .nfs1234’. Note, however, this will only work on the machine where the processes that has the file open is running. So, if your process is running on bobac and you run the lsof on some other burrow machine, you won’t see anything.

　　For example:

　　% echo test > foo
　　% tail -f foo
　　test
　　^Z
　　Suspended
　　% rm foo
　　% ls -A
　　.nfsB23D
　　% rm .nfsB23D
　　% ls -A
　　.nfsC23D
　　% lsof .nfsC23D
　　COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
　　tail 1257 robh 0r VREG 176,6 5 3000753 .nfsC23D
　　%

　　So, once you have located and killed the process that has the file open, the .nfs file will go away automatically. In the above example, when you kill the tail process, the .nfsC23D file will disappear.

　　The useful tools: ps, lsof