Fullzero thanks for detailed instruction of my idea and including it into nvOS v0017

here are some operations for image space releasing:

sudo apt update
sudo apt upgrade

sudo du -sh /var/cache/apt/archives
sudo apt-get clean

sudo apt-get autoremove
if after such operation we have such mistake as:
===
Errors were encountered while processing:
 linux-image-extra-4.4.0-65-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)
===
we need to delete all failes manually:
ls /var/lib/dpkg/info/ | grep linux-image | grep 4.4.0-65

exactly:
====
linux-image-4.4.0-65-generic.list
linux-image-4.4.0-65-generic.postrm
linux-image-extra-4.4.0-65-generic.list
linux-image-extra-4.4.0-65-generic.md5sums
linux-image-extra-4.4.0-65-generic.postinst
linux-image-extra-4.4.0-65-generic.postrm
====

cd /var/lib/dpkg/info/
sudo rm linux-image-4.4.0-65-generic.list
sudo rm linux-image-4.4.0-65-generic.postrm
sudo rm linux-image-extra-4.4.0-65-generic.list
sudo rm linux-image-extra-4.4.0-65-generic.md5sums
sudo rm linux-image-extra-4.4.0-65-generic.postinst
sudo rm linux-image-extra-4.4.0-65-generic.postrm

repeat the command:

sudo apt-get autoremove

have to delete non usable linux-image in system

dpkg --list | grep linux-image

sudo apt-get purge linux-image-4.4.0-{31,59,62,64,65,66,72,75,78,79}
sudo apt-get purge linux-image-extra-4.4.0-31-generic
sudo apt-get purge linux-image-extra-4.4.0-31-generic
sudo apt-get purge linux-image-extra-4.4.0-59-generic
sudo apt-get purge linux-image-extra-4.4.0-62-generic
sudo apt-get purge linux-image-extra-4.4.0-64-generic
sudo apt-get purge linux-image-extra-4.4.0-66-generic
sudo apt-get purge linux-image-extra-4.4.0-72-generic
sudo apt-get purge linux-image-extra-4.4.0-75-generic
sudo apt-get purge linux-image-extra-4.4.0-78-generic
sudo apt-get purge linux-image-extra-4.4.0-79-generic

then exsecute

sudo apt-get -f install
sudo dpkg --configure -a

it allows to descrease size image on 2++Gb


PS:I would like to add monitoring system into your project.
Now, I'm choosing from zabbix, munin and cacti. What would you advice?