How to upgrade 16.04.3 to 16.04.4 early preview?

[vincent-hui]

Where can download 16.04.4 early preview? and how to upgrade 16.04.3 to 16.04.4 early preview?

Thanks

[deadflowr]

You can get the xenial dauily build here:
http://cdimages.ubuntu.com/xenial/daily-live/current/
and you can enable the -proposed repository to get an early preview of what's to come.
Fair warning that proposed is all about early testing so don't be surprised if something breaks with it enabled.
https://wiki.ubuntu.com/Testing/EnableProposed

Note you have over a month before the current planned release of 16.04.4 (Marked currently as February 15th)
So not much may be any different from enabling proposed or downloading the daily build.