How can I centrally manage computers on ubuntu server?

Question

ubuntu

At home there are several (<10) virtual machines with ubuntu server 14.04 on board, a system is required that
1. can see the status of the CPU / memory, possibly get a list of processes,
2. monitor package updates and inform about the need for an update;
3. with the ability to manage (create, change) users and groups on computers;
4. with a web interface that is not loaded with unnecessary functions (or with the ability to turn off their display)
5. requiring no more than 256MB per server machine and the same amount for client parts (if any)
Notes:
If there is a desktop alternative to the one described above under OS X, I will consider it.
Console solutions like apt-dater are not suitable.
Landscape not to offer, I did not get along with him. Too big, a lot of unnecessary functions for me, eats memory.
I do not need a virtual machine management system, we will assume that I create them with handles.

Answer 1

Look towards Chef / Salt / Puppet as management systems
How to monitor system - Zabbix / Graphite
You can also look towards docker

Answer 2

Set yourself ProxMox as a hypervisor, it's all there in the webmord, albeit in a very simple form, as an alternative:
1) zabbix (can work both with the hypervisor itself and its API, and separately with virtual machines)
2) Don't want Landscape, write a script check for zabbix yourself, you will see right in the monitoring when you need an update or an email to receive.
3) A single RADIUS server as an option, or any of the orchestration systems, ansible is convenient for administration
Well, as an option, buy some crap from virtual machine control panels, such as VMmanager.