Enlarge disks by removing reserve space on ext2/3/4

Five percent of a ext2/3/4 filesysteem is reserved
for root. 
 
 With tune2fs this can be tweaked, even after the filesystem is
created. 
 
 # tune2fs -m 1 /dev/sda1 
 this reserves 1 percent. 
 # tune2fs -m 0.2 /dev/sda1 
 this reserves 0.2 percent 
 
 On a filesystem that has no systemfiles, like homedirs, there is no
use for any reserved space. You can make this 0 percent.