df reports that the root partition is almost full, but the reason is not found with du

Issue

• df reports that the root partition is almost full, but the reason is not found with du.

  # df -h
  Filesystem            Size  Used Avail Use% Mounted on
  /dev/sda5              20G   20G     0 100% /
  /dev/sda10            186G  293M  176G   1% /backup1
  /dev/sda9             3.0G   70M  2.7G   3% /home
  /dev/sda8             3.9G  126M  3.6G   4% /tmp
  /dev/sda7             7.8G  2.6G  4.9G  35% /usr
  /dev/sda6             7.8G  2.9G  4.5G  39% /var
  /dev/sda3              20G  721M   18G   4% /opt
  /dev/sda1              99M   14M   80M  15% /boot
  tmpfs                 5.8G     0  5.8G   0% /dev/shm
  
  
  
  # find / -maxdepth 1 | egrep -v "^/$|/backup1|/home|/tmp|/usr|/var|/opt|/boot" | xargs du -sh
  0       /.autofsck
  8.0K    /mnt
  22M     /lib64
  6.3M    /root
  123M    /lib
  8.5G    /u01
  16K     /lost+found
  0       /sys
  8.2M    /bin
  0       /.autorelabel
  0       /proc
  93M     /etc
  180K    /dev
  8.0K    /media
  8.0K    /selinux
  8.0K    /srv
  33M     /sbin
  

• There are no 'deleted' files found in lsof output.

• Issue persists across reboots.