Why is df command showing 100% usage although less than 100% is used?

Products

• XOS

Issue/Introduction

When a disk partition is nearly full, the df command shows zero available disk space and 100% of disk used. For example:
 

[[email protected] admin]# df -h /tftpboot
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/d1vg-lv3  201G  192G     0 100% /tftpboot

 

Cause

The file system on the CPM marks 5% of the available disk capacity as reserved. If less than 5% is free, using the remaining reserved space requires root privileges. Any non-privileged users and processes are unable to write new data to the partition.

On a large partition like in this example (201GB), the reserved 5% represent about 10GB of disk capacity. Such partition with more than 191GB utilized space will be shown as 100% full because 100% of the non-reserved space is used.
 

Resolution

To restore disk write access for non-privileged users and processes, it is necessary to identify files that can be deleted and free up the disk space. Once the 5% threshold is crossed, the Use percentage drops bellow 100%:
 

[[email protected] admin]# df -h /tftpboot

Filesystem            Size  Used Avail Use% Mounted on

/dev/mapper/d1vg-lv3  201G  188G  2.5G  99% /tftpboot

Workaround

N/A