If you have ever noticed, the ext filesystems have some amount of space reserved. Hence the actual free space available on disk is little less. This reserved space is kept to keep your computer running in situations when your disk get full. Hence it is recommended to keep some decent amount of reserved space for root partition.
Usually default is not a problem for partitions of small size, but lets say when you have partition of 200GB, around 5% of it reserved by default, which is 10GB. 10GB is pretty much too much for this. Also if you have created some auxiliary partition just to dump data, which is not required by your system (not root, home, var etc..) you can set reserve space to 0 as its just not needed there, hence giving you GB’s of more space.
We’ll use a command line program tune2fs to do that. tune2fs is a utility to help you change various parameters of ext2/ext3/ext4 filesystems.
First of all find the partition whose reserved space quota you would like to change.
# fdisk -l
If you want to, you can see the number of reserved blocks using:
# tune2fs -l /dev/sd[x][y]
Now change reserve quota using following command.
# tune2fs -m <new_quota_percentage> /dev/sd[x][y]
For example, if I want to set reserved space to 2% for my second partition on first hardisk. I will, execute this:
# tune2fs -m 2 /dev/sda2