laney@nightingale> chdist create xenial http://archive.ubuntu.com/ubuntu xenial "main universe multiverse restricted" ~
Run chdist apt-get xenial update
And enjoy.
laney@nightingale> chdist apt-get xenial update ~
Get:1 http://archive.ubuntu.com/ubuntu xenial InRelease [247 kB]
Get:2 http://archive.ubuntu.com/ubuntu xenial/main Sources [866 kB]
Get:3 http://archive.ubuntu.com/ubuntu xenial/universe Sources [7,760 kB]
Get:4 http://archive.ubuntu.com/ubuntu xenial/multiverse Sources [182 kB]
Get:5 http://archive.ubuntu.com/ubuntu xenial/restricted Sources [4,808 B]
Get:6 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages [1,184 kB]
Get:7 http://archive.ubuntu.com/ubuntu xenial/main Translation-en_GB [426 kB]
Get:8 http://archive.ubuntu.com/ubuntu xenial/main Translation-en [563 kB]
Get:9 http://archive.ubuntu.com/ubuntu xenial/universe amd64 Packages [7,543 kB]
Get:10 http://archive.ubuntu.com/ubuntu xenial/universe Translation-en_GB [3,040 kB]
Get:11 http://archive.ubuntu.com/ubuntu xenial/universe Translation-en [4,362 kB]
Get:12 http://archive.ubuntu.com/ubuntu xenial/multiverse amd64 Packages [146 kB]
Get:13 http://archive.ubuntu.com/ubuntu xenial/multiverse Translation-en_GB [88.1 kB]
Get:14 http://archive.ubuntu.com/ubuntu xenial/multiverse Translation-en [107 kB]
Get:15 http://archive.ubuntu.com/ubuntu xenial/restricted amd64 Packages [8,344 B]
Get:16 http://archive.ubuntu.com/ubuntu xenial/restricted Translation-en_GB [2,556 B]
Get:17 http://archive.ubuntu.com/ubuntu xenial/restricted Translation-en [2,908 B]
Fetched 26.5 MB in 8s (3,238 kB/s)
Reading package lists... Done
laney@nightingale> chdist apt-cache xenial search snapd ~
snapd - Tool to interact with Ubuntu Core Snappy.
ubuntu-core-snapd-units - Scripts for snapd that should only run on ubuntu core systems.