/dev/mapper/fedora-root full to 96%, but more than 50% of the weight seems to be hidden
<p>The facts:</p>
<pre><code># ls -lh /
total 80K
drwxrwxrwx.   5 root root 4.0K May 26  2015 backUp
lrwxrwxrwx.   1 root root    7 Aug 16  2014 bin -&gt; 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 -&gt; usr/lib
lrwxrwxrwx.   1 root root    9 Aug 16  2014 lib64 -&gt; 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 -&gt; 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
</code></pre>
<p>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.</p>
<ul>
<li>the <strong>df -h</strong> command returns that the / is full to 96%:</li>
</ul>
<blockquote>
<p>/dev/mapper/fedora-root   50G   45G  2.3G  96% /</p>
</blockquote>
<ul>
<li>But if we take the return of the <strong>du -sh</strong> for the /, we observe that the more heavy directories are the /usr et /var, with a total weight of roughly 13G (/backUp, /data_1 and /data_2 are on other disks and /home correspond to /dev/mapper/fedora-home):</li>
</ul>
<blockquote>
<p>9.3G  /usr</p>
<p>2.9G  /var</p>
</blockquote>
<p>Thus, it appears that the / from the <strong>du</strong> command is weighting nearly 13G and from <strong>df</strong> 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 ...</p>