df show bigger disk usage than du

Issue: Why does df show bigger disk usage than du? Resolution: There are some instances where df would output a bigger disk usage than du. The most common instance is when a process has opened a huge file and that same file is deleted with rm. Technically, the file still exists because a process still has an open file descriptor associated with that file. An example is presented below. First, a 200Mb file called bigfile is created and is opened using the vi editor:

[root@localhost ~]# ls -lh bigfile

-rw-r--r-- 1 root root 200M Dec 22 14:53 bigfile

[root@localhost ~]# lsof|grep bigfile vi 23824 root 3r REG 3,2 209715200 2052534 /root/bigfile vi 23824 root 4u REG 3,2 4096 2052542 /root/.bigfile.swp At this point, both df and du would have the same output:

[root@localhost ~]# df -h / Filesystem Size Used Avail Use% Mounted on /dev/hda2 19G 8.8G 8.4G 51% /

[root@localhost ~]# du -sh / 8.8G / Now the discrepancy in output shows once bigfile is deleted:

[root@localhost ~]# rm -f bigfile

[root@localhost ~]# df -h /

Filesystem Size Used Avail Use% Mounted on /dev/hda2 19G 8.8G 8.4G 51% /

[root@localhost ~]# du -sh / 8.6G / Killing the vi process that has opened bigfile resolves the discrepancy:

[root@localhost ~]# kill 23824

[root@localhost ~]# df -h / Filesystem Size Used Avail Use% Mounted on /dev/hda2 19G 8.6G 8.6G 50% /

[root@localhost ~]# du -sh 8.6G /