Strange problem…

Why i have full / partition used, but it's not really used?

Fast info:

xwing ~ # df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs           16G   15G   75M 100% /
/dev/root        16G   15G   75M 100% /
devtmpfs        5,9G     0  5,9G   0% /dev
tmpfs           5,9G  552K  5,9G   1% /run
rc-svcdir       1,0M   72K  952K   8% /lib64/rc/init.d
cgroup_root      10M     0   10M   0% /sys/fs/cgroup
shm             5,9G     0  5,9G   0% /dev/shm
cachedir        4,0M  4,0K  4,0M   1% /lib64/splash/cache
/dev/sda1       124M   43M   76M  36% /boot
/dev/sda5        63G   25G   36G  42% /home
/dev/sda6       483G  147G  312G  33% /mnt/data
tmpfs           8,0G     0  8,0G   0% /var/tmp/portage

Maybe i-nodes? Noo…

xwing ~ # df -i
Filesystem       Inodes  IUsed    IFree IUse% Mounted on
rootfs          1048576 548459   500117   53% /
/dev/root       1048576 548459   500117   53% /
devtmpfs        1525561    517  1525044    1% /dev
tmpfs           1525918    374  1525544    1% /run
rc-svcdir       1525918     61  1525857    1% /lib64/rc/init.d
cgroup_root     1525918      5  1525913    1% /sys/fs/cgroup
shm             1525918      1  1525917    1% /dev/shm
cachedir        1525918      2  1525916    1% /lib64/splash/cache
/dev/sda1         32768    314    32454    1% /boot
/dev/sda5       4194304 145765  4048539    4% /home
/dev/sda6      32153600  11325 32142275    1% /mnt/data
tmpfs           1525918      1  1525917    1% /var/tmp/portage

But:

xwing ~ # du -sxh /
8,3G    /

Maybe i have something broken in mount? (but anyway, notice i used du with -x which calculates files ONLY from / filesystem…)

/spaces added by me for better readibility/

xwing ~ # mount
rootfs      on /                        type rootfs   (rw)
/dev/root   on /                        type ext4     (rw,noatime,data=ordered)
devtmpfs    on /dev                     type devtmpfs (rw,relatime,size=6102244k,nr_inodes=1525561,mode=755)
proc        on /proc                    type proc     (rw,nosuid,nodev,noexec,relatime)
tmpfs       on /run                     type tmpfs    (rw,nosuid,nodev,relatime,mode=755)
rc-svcdir   on /lib64/rc/init.d         type tmpfs    (rw,nosuid,nodev,noexec,relatime,size=1024k,mode=755)
sysfs       on /sys                     type sysfs    (rw,nosuid,nodev,noexec,relatime)
debugfs     on /sys/kernel/debug        type debugfs  (rw,nosuid,nodev,noexec,relatime)
cgroup_root on /sys/fs/cgroup           type tmpfs    (rw,nosuid,nodev,noexec,relatime,size=10240k,mode=755)
cpuset      on /sys/fs/cgroup/cpuset    type cgroup   (rw,nosuid,nodev,noexec,relatime,cpuset)
cpu         on /sys/fs/cgroup/cpu       type cgroup   (rw,nosuid,nodev,noexec,relatime,cpu)
cpuacct     on /sys/fs/cgroup/cpuacct   type cgroup   (rw,nosuid,nodev,noexec,relatime,cpuacct)
freezer     on /sys/fs/cgroup/freezer   type cgroup   (rw,nosuid,nodev,noexec,relatime,freezer)
devpts      on /dev/pts                 type devpts   (rw,nosuid,noexec,relatime,gid=5,mode=620)
shm         on /dev/shm                 type tmpfs    (rw,nosuid,nodev,noexec,relatime)
cachedir    on /lib64/splash/cache      type tmpfs    (rw,nosuid,nodev,noexec,noatime,size=4096k,mode=755)
/dev/sda1   on /boot                    type ext2     (rw,noatime)
/dev/sda5   on /home                    type ext4     (rw,noatime)
/dev/sda6   on /mnt/data                type ext4     (rw,noatime)
tmpfs       on /var/tmp/portage         type tmpfs    (rw,size=8G)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)

Kernel:

morsik@xwing ~ $ uname -a
Linux xwing 3.6.2-gentooxwing #8 SMP Sun Oct 21 21:36:53 CEST 2012 x86_64 Intel(R) Core(TM) i7-3610QM CPU @ 2.30GHz GenuineIntel GNU/Linux

Really… I'm out of possible ideas about it.

What i tried:

• check if there are some fd still open after rm -rf /usr/portage/distfiles/*
• sync
• reboot
• fsck

EDIT AND SOLUTION:

As always i found solution after asking for help (-;

Mounting (as Luke404 said) / partition somewhere else and doing du -sh /mnt/something told there's 15G of data, so the same like in df.

What was the problem?

mount!

I created /home partition later, added to /etc/fstab, I copied files from /home (on / partition) to /home (on /home partition) but i FORGOT to remove files from /home at / partition.

So I still had my old files on /home (on / partition).

But why du -sxh told me 8G? Easy…

-x forces to not check different mountpoints, so… it didn't checked /home while it was mounted. And there was my missing /home.

Thanks to Luke404 and pidpawel who helped me on IRC.

After writing this EDIT section i saw answers here, and Scrivener got point here!

Stupid problems are stupid (-;