The plugins required command lists all plugins required by a Packer config and
all the installed binaries that match the constraint. The first binary
is the most up-to-date installed version and will be the one picked by Packer in a build.
$ packer plugins required -h
Usage: packer plugins required <path>
This command will list every Packer plugin required by a Packer config, in
packer.required_plugins blocks. All binaries matching the required version
constrain and the current OS and Architecture will be listed. The most recent
version (and the first of the list) will be the one picked by Packer during a
build.
Ex: packer plugins required require.pkr.hcl
Ex: packer plugins required path/to/folder/
packer init will install all required plugins.