How can I check how much space there is left on WUBI versus how much space it takes on my HDD?

Using 11.10 for the record. It would be easiest to do it on the Terminal.

You can do it as follows:

bcbc@ubuntu:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/loop0       15G  7.3G  7.0G  51% /
udev            1.9G  4.0K  1.9G   1% /dev
tmpfs           751M  920K  750M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            1.9G  416K  1.9G   1% /run/shm
/dev/sda3       295G  113G  183G  39% /host
bcbc@ubuntu:~$

This shows that the Wubi virtual disk is mounted as / on /dev/loop0 and is 15G in size with 7G free. If you had more thane one virtual disk you'd see perhaps /dev/loop1 mounted on /home.

It also shows that the Windows /host is 295G in size and has 183G free.

What to do if you're short on space

1. Clean up cache
2. Use baobab to check where your space is gone
3. Remove all but the most recent 2 working kernels
4. Resize the virtual disk
5. Migrate to a partition

1. Clean up cache

sudo apt-get autoremove

sudo apt-get autoclean

2. Use the disk usage analyzer

From a command line run: gksu baobab

Make sure you go to Edit, Preferences and uncheck the Windows /host partition before scanning the file system or it will scan your Windows /host as well.

3. Remove old kernels There are various ways to do this. Just make sure you keep the two most recent working kernels. Each kernel can free up about 190MB.

Here's one method to do this (via Kees Cook):

OLD=$(ls -tr /boot/vmlinuz-* | head -n -2 | cut -d- -f2- | awk '{print "linux-image-" $0}')

if [ -n "$OLD" ]; then sudo apt-get -q remove --purge $OLD; fi

That's probably better in a script, but if you enter each line, it does the trick. You can use synaptic package manager for this, but I understand this isn't installed by default anymore.

4. Resize a Wubi install You can do an in-place resize of the virtual disk Wubi uses or make a new, larger disk. The former must be run from a live CD and is quickest, but the latter can be done from a running Wubi install.

5. Migrate a Wubi install See how-to-convert-wubi-install-into-regular-install