File system bafflement

[Paul Smith]

On Tue, 2014-09-02 at 20:30 +0100, R Kimber wrote:
> It's starting to look like a complete re-install .....

Nope.  Totally unnecessary.  You need to follow the advice others have
provided, which is to boot into a live CD then mount the "/" partition
from your disk, then clean it up.

What has happened is this:

At some point before you had all those other partitions mounted, you
created a directory on the root partition with the same name as one of
your (future) partitions.  Then you added a bunch of files into it that
are taking up a lot of space (about 3G or so it looks like).  These
files exist in the root partition.

Then you created the partitions and specified the mount point of the
partition to be the already-existing directory.

Now that you have mounted the partition, the content that is there on
the root partition is hidden: you can't get to it, so you can't delete
it.  The only way to get to it is to unmount the partition that is
"hiding" the content.

Since you don't know which partition it is, you can either (a) umount
them one at a time and after unmounting each one check the mount
directory and see if there's stuff in there that can be deleted, or (b)
reboot your system into a live CD image, where none of your partitions
are mounted, then mount the root partition only without mounting the
others and clean it out that way.

In general it's best to always be sure that any directories you want to
use for mount points are empty before using them.