시스템에서 여유 공간이 거의 없다고 보고하지만 총계가 합산되지 않습니다.

저는 데비안 6.x를 실행하고 있습니다.

df -h나에게 이것을 말해주세요 :

# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              19G   17G  696M  97% /
....

하지만 숫자는 합산되지 않습니다 ...

# for D in $(ls -1 / | grep -vE "(home|media)"); do echo -n "$D ..........."; du -ch $D | grep total; done;
bin ...........6.0M     total
boot ...........14M     total
dev ...........256K     total
etc ...........19M      total
initrd.img ...........0 total
lib ...........96M      total
lost+found ...........16K       total
mnt ...........4.0K     total
opt ...........4.0K     total
proc ...........du: cannot access `proc/25117/task/25117/fd/3': No such file or directory
du: cannot access `proc/25117/task/25117/fdinfo/3': No such file or directory
du: cannot access `proc/25117/fd/3': No such file or directory
du: cannot access `proc/25117/fdinfo/3': No such file or directory
0       total
root ...........643M    total
sbin ...........4.7M    total
selinux ...........4.0K total
srv ...........200K     total
sys ...........0        total
tmp ...........308K     total
usr ...........4.0K     usr/src/linux-headers-2.6.32-5-686/include/config/mtdram/total
4.5G    total
var ...........677M     total
vmlinuz ...........0    total

재부팅했는데 동일하게보고됩니다. 내가 무엇을 놓치고 있나요? 차이점은 어디에 있습니까?