Hello all,
I finally managed to install nethunter on my nexus 4 (since there is no prebuilt binary for lollipop, i had to clone the git repo and build it myself, but fortunately it was straightforward).
Now I have another problem, I can't install chroot

The chroot manager says that chroot is too big and I need 8 gig of free space..
I do have 4.8 Gb of free space on my nexus 4.

1) So, why the app says "available size of partition 0 MB"?
2) I tried to circumvent the 8 Gb check by un-tar manually through shell.. I tried this command

# tar xJvf /sdcard/kalifs.tar.xz -C /data/local/nhsystem

found here

but even after the successful un-tar, the app still says chroot is not installed.
What else should I do to make the nethunter app recognize my manually installed chroot?
I saw that the minimal chroot unzipped is just 600 Mb.. so it really makes sense to impose 8 Gb of free space?

Thank you all for your support.