Don't understand df/du output

[Rodrigo Gonzalez]

On 08/12/2011 06:58 PM, Alain AUDEBERT aka 2A wrote:
> Hello list,
>
> I having a problem to understand the output of du and df command :
>
> [root at ftp ~]# df -h /opt/
> Filesystem    Size    Used   Avail Capacity  Mounted on
> /dev/xbd6     387G    342G     13G    96%    /opt
>
> [root at ftp ~]# du -sh /opt/
> 342G    /opt/
>
> But 387Go - 342Go not equal to 13Go ! Where's the available space ?
> (same thing with df -k)
>
> I have try a tunefs -m 1 /dev/xbd6, unmount, mount and nothing change
> Is it the 8% reserved by FFS ?
Yes

read http://www.freebsd.org/doc/en/books/faq/disks.html

Question *9.27* (last one)

>
> Regards,
>
> Alain
>