For all my NTFS partitions, Ubuntu always shows 1~2GB more free space than Windows. What's the cause of this? Will some of my files be overwritten just because Ubuntu thinks there is more free space than there actually is?
They measure the sizes differently by default. Under Linux, you can specify the
--si parameter (which uses powers of 1000 not 1024) with
du to get numbers that match up with how Windows calculates the sizes.
$ df -h Filesystem Size Used Avail Use% Mounted on /dev/sda1 119G 29G 89G 25% /
$ df --si Filesystem Size Used Avail Use% Mounted on /dev/sda1 127G 31G 96G 25% /
And on a file level
$ du -sh justbrowsing_20140331_nightly.iso 589M justbrowsing_20140331_nightly.iso
$ du --si justbrowsing_20140331_nightly.iso 617M justbrowsing_20140331_nightly.iso
Explained in-depth here
Free space in filesystems is always just a guess. Different numbers may mean different representations or different results of guessing. I wouldn't be afraid of that.