customized-core.txt

% snap download -h
Usage:
  snap download [download-OPTIONS] <snap>

The download command downloads the given snap and its supporting assertions
to the current directory with .snap and .assert file extensions, respectively.

[download command options]
          --channel=   Use this channel instead of stable
          --edge       Install from the edge channel
          --beta       Install from the beta channel
          --candidate  Install from the candidate channel
          --stable     Install from the stable channel
          --revision=  Download the given revision of a snap, to which you must have developer access

[download command arguments]
  <snap>:              Snap name

% snap info core
name:      core
summary:   snapd runtime environment
publisher: canonical
contact:   snappy-canonical-storeaccount@canonical.com
license:   unknown
description: |
  The core runtime environment for snapd
type:         core
snap-id:      99T7MUlRhtI3U0QFgl5mXXESAiSwt776
tracking:     edge
refresh-date: today at 16:04 CST
channels:                                       
  stable:    16-2.32.8              (4650) 90MB -
  candidate: 16-2.32.8              (4650) 90MB -
  beta:      16-2.33                (4830) 91MB -
  edge:      16-2.33+git783.1bf9333 (4846) 91MB -
installed:   16-2.33+git783.1bf9333 (4846) 91MB core

% snap download --revision=4846 core
Fetching snap "core"
Fetching assertions for "core"
Install the snap with:
   snap ack core_4846.assert
   snap install core_4846.snap

ubuntu-image --image-size 4G --extra-snaps core_4846.snap model 
Copying "core_4846.snap" (core)
Fetching pc
core already prepared, skipping