The facts:
# ls -lh /
total 80K
drwxrwxrwx. 5 root root 4.0K May 26 2015 backUp
lrwxrwxrwx. 1 root root 7 Aug 16 2014 bin -> usr/bin
dr-xr-xr-x. 4 root root 3.0K Jan 5 14:13 boot
drwxrwxrwx. 6 root root 4.0K Jul 16 12:01 data_1
drwxrwxrwx. 5 root root 4.0K Jun 10 2015 data_2
drwxr-xr-x. 20 root root 3.6K Jan 6 09:29 dev
drwxr-xr-x. 160 root root 12K Jan 6 10:28 etc
drwxr-xr-x. 4 root root 4.0K Aug 16 2014 home
drwxr-xr-x. 2 root root 0 Jan 6 09:56 hosts
lrwxrwxrwx. 1 root root 7 Aug 16 2014 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 Aug 16 2014 lib64 -> usr/lib64
drwx------. 2 root root 16K Nov 4 2014 lost+found
drwxr-xr-x. 2 root root 4.0K Aug 16 2014 media
drwxr-xr-x. 2 root root 4.0K Aug 16 2014 mnt
drwxr-xr-x. 4 root root 4.0K Jul 17 17:43 opt
dr-xr-xr-x. 295 root root 0 Jan 6 10:29 proc
dr-xr-x---. 25 root root 4.0K Jan 6 10:51 root
drwxr-xr-x. 46 root root 1.4K Jan 6 10:46 run
lrwxrwxrwx. 1 root root 8 Aug 16 2014 sbin -> usr/sbin
drwxr-xr-x. 2 root root 4.0K Aug 16 2014 srv
dr-xr-xr-x. 13 root root 0 Jan 6 09:29 sys
drwxr-xr-x. 2 root root 4.0K Jul 15 16:25 sysroot
drwxrwxrwt. 14 root root 300 Jan 6 10:56 tmp
drwxr-xr-x. 14 root root 4.0K Sep 14 16:57 usr
drwxr-xr-x. 20 root root 4.0K Jan 6 10:29 var
# df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 32G 0 32G 0% /dev
tmpfs 32G 308K 32G 1% /dev/shm
tmpfs 32G 1.5M 32G 1% /run
tmpfs 32G 0 32G 0% /sys/fs/cgroup
/dev/mapper/fedora-root 50G 45G 2.3G 96% /
tmpfs 32G 328K 32G 1% /tmp
/dev/sda3 477M 147M 301M 33% /boot
/dev/sdb2 917G 288G 583G 34% /data_2
/dev/sdb1 917G 20G 852G 3% /data_1
/dev/mapper/fedora-home 160G 13G 140G 9% /home
/dev/sdc1 2.7T 383G 2.2T 15% /backUp
tmpfs 6.3G 8.0K 6.3G 1% /run/user/42
tmpfs 6.3G 36K 6.3G 1% /run/user/1385
# pvdisplay
--- Physical volume ---
PV Name /dev/sda5
VG Name fedora
PV Size 235.95 GiB / not usable 0
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 60402
Free PE 0
Allocated PE 60402
PV UUID 8oXP7e-NSTf-weml-tWWg-E64b-mjmq-nzcf19
# lvdisplay
--- Logical volume ---
LV Path /dev/fedora/swap
LV Name swap
VG Name fedora
LV UUID Ego2By-VwgS-bIic-Wwna-D5u8-4JDi-9gVAez
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2014-11-04 12:35:40 +0100
LV Status available
# open 2
LV Size 23.85 GiB
Current LE 6105
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0
--- Logical volume ---
LV Path /dev/fedora/home
LV Name home
VG Name fedora
LV UUID uPHuWm-rdMX-AOt9-MJWP-5Qgs-a83u-Asqktc
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2014-11-04 12:35:40 +0100
LV Status available
# open 1
LV Size 162.10 GiB
Current LE 41497
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:2
--- Logical volume ---
LV Path /dev/fedora/root
LV Name root
VG Name fedora
LV UUID PQG3IH-2lt3-PCyq-c6by-fSxL-2a2L-Hlr87V
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2014-11-04 12:35:46 +0100
LV Status available
# open 1
LV Size 50.00 GiB
Current LE 12800
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1
# du -sh /*
382G /backUp
0 /bin
145M /boot
20G /data_1
288G /data_2
308K /dev
42M /etc
12G /home
0 /hosts
0 /lib
0 /lib64
16K /lost+found
4.0K /media
4.0K /mnt
137M /opt
du: cannot access ‘/proc/13761/task/13761/fd/3’: No such file or directory
du: cannot access ‘/proc/13761/task/13761/fdinfo/3’: No such file or directory
du: cannot access ‘/proc/13761/fd/3’: No such file or directory
du: cannot access ‘/proc/13761/fdinfo/3’: No such file or directory
0 /proc
35M /root
du: cannot access ‘/run/user/1385/gvfs’: Permission denied
du: cannot access ‘/run/user/42/gvfs’: Permission denied
1.5M /run
0 /sbin
4.0K /srv
0 /sys
4.0K /sysroot
4.0K /tmp
9.3G /usr
2.9G /var
So, according to these results, /backUp, /data_1 and /data_2 are mounted on two disks (/dev/sdc and /dev/sdb respectively) and the system in an other disk (/dev/sda) with LVM.
/dev/mapper/fedora-root 50G 45G 2.3G 96% /
9.3G /usr
2.9G /var
Thus, it appears that the / from the du command is weighting nearly 13G and from df command nearly 45G ... So I have 32G in a black hole ... I do not see the error, please do not hesitate to give advice to fix this very strange things !I am sure that I miss something ...
I lost a lot of time for finally a very easy thing. As proposed in comment by mattdm, in this case the more easy and quick thing to try is to unmount all the volumes (except the system, of course) and check if data exist again in the mount point. The problem can comes in the case of an automatic backup each day (as I do). If for an unknown reason the corresponding disk is unpluged (or other) the backup will be done on the root file (the mounting point). If the disk is then mounted (again for an unknow reason - the date for this problem corresponds to christmas vacation :-)) , the corresponding data on the root file will be obscured !!!! For the long version see here. Hope this will help.