I made two custom boxes, so far:
Create custom box and upload to Atlas
You'll need an account on Atlas.
After you launched VM from vagrant by:
$ vagrant up
You can create
.box file by:
$ vagrant package --output foo.box
Then, you can upload your box from this page.
Reuse box without uploading to Atlas.
In this case, you don't need an account on Atlas.
.box file you created above, you can use
vagrant box add command for registering on local:
$ vagrant box add foo.box --name hiogawa/foo
Then, you can resue from anywhere on the same pc by:
$ vagrant init hiogawa/foo