linux tune2fs reserve diskspace for privileged process
tune2fs -m 0 /dev/hdb5
-m reserved-blocks-percentage
Set the percentage of the filesystem which may only be allocated by privileged processes. Reserving some number of
filesystem blocks for use by privileged processes is done to avoid filesystem fragmentation, and to allow system daemons,
such as syslogd(8), to continue to function correctly after non-privileged processes are prevented from writing to the
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filesystem. Normally, the default percentage of reserved blocks is 5%.