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


Article ID: 168604


Updated On:




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



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.


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