[CentOS] df -h shows system at 100% used, but there is space left

[Dnk]

On 24-Apr-09, at 10:00 AM, Laurentiu Coica <laurentiu.coica at gmail.com>  
wrote:

> On Fri, Apr 24, 2009 at 7:43 PM, dnk <d.k.emaillists at gmail.com> wrote:
>> Has anyone seen output like this before? Notice on my /dev/md0 That  
>> it
>> reports 100% used, but also 5.3 Gb available. What would cause this?
>>
> Because when an ext2/3 file system is formated by default 5% is
> reserved for root
> Use
>  tune2fs  -m reserved-blocks-percentage
>
>>
> -- 
> Laurentiu Coica
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> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos

What does that command do exactly?

Thanks in advance.

D