How to Reclaim Reserved Space On EXT4 Partitions

However, this is only really needed for your Linux partition, so if you have an external EXT4 drive, or have an EXT4 partition on your internal drive (other than the one your system is on), you are needlessly wasting space (40Gb of the drive in the example). But you can free up that disk space quite easily, without having to re-partition the drive or anything. All it takes is a couple of commands pasted into the terminal.

In the following example, an external hard-drive will have the reserve set to 0 (zero), since this is what most people will need this for. First, we have to determine the device name, as using its mounted name – /media/700Gb Ext4 – won’t suffice. To do so, enter the following into the terminal:
mount|grep ^'/dev'

Look for the line containing your device:
/dev/sdc1 on /media/700Gb Ext4 type ext4 (rw,nosuid,nodev,uhelper=udisks)
… and you can see what it is named (/dev/sdc1 in this case). To free up reserved space, enter the following (replacing /dev/sdc1 with whatever the appropriate device name is, if need be – just make sure you don’t do it to your main drive!):
sudo tune2fs -m 0 /dev/sdc1

You should then be presented with the following message:
Setting reserved blocks percentage to 0% (0 blocks)

To confirm all has gone well, you can right-click an empty area of the folder window for the device and choose Properties, then compare the free space from before and after, or run the following command (once again replacing the device name with the correct one in your case):
sudo tune2fs -l /dev/sdc1 | grep 'Reserved block count'
You should be greeted with the following:
Reserved block count: 0

That’s it – you now have all of your drive to use.

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Note: if you receive the following error message:

tune2fs: Bad magic number in super-block while trying to open /dev/sdb1
Couldn’t find valid filesystem superblock.

… then the filesystem likely isn’t EXT4 – chances are the drive is actually formatted as NTFS or FAT for use on Windows systems (which would be the case if you’ve bought an external drive, and never did anything other than copy files to it). You would have needed to partition/format the drive to EXT4, so if you didn’t, then you actually don’t need this guide.

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