有时候会遇到这样的问题：df -h统计一个目录，显示有约100M可用空间，使用了5G；而用du -sh统计该目录下的文件大小，却发现总共才占用了1G。也就是说，二者统计结果差距巨大。
例如：
df-h /tmp/
结果：
3.9G 3.5G 220M 95% /tmp
du-sh /tmp/
结果：
132K /tmp/
结果差异巨大。
引用网上的一段话，原因是这样的：

（1）This section gives the technical explanation of why du and df sometimes report different totals of disk space usage. When a program that is running in the background writes to a file while the process is running, the file to which this process is writing is deleted. Running df and du shows a discrepancy in the amount of disk space usage. The df command shows a higher value. （2）The difference is that whenever an application has an open file, but the file is already deleted, then it is counted in the df output (because the space is certainly not free) but not in du (because it is not being used by a file).

如何查看是什么进程导致的问题？
假设你发现是 /tmp/ 目录不对劲，那么就这样就可以查看：
lsof| grep /tmp/
输出的结果中，注意某些含有“(deleted)”字样的记录，它们中的一部分就是罪魁祸首，将它们kill掉即可（如果可以重启这些进程所对应的服务的话，也有可能解决问题）。