Joshua Johnson - KC5JMJ

i've been following this site
as a starting ground but started coming up with errors


install-dvswitch-repo                                           100%[========================================================================================

2020-12-13 17:34:53 (13.7 MB/s) - ‘install-dvswitch-repo’ saved [782/782]

root@bridge:/tmp# chmod +x install-dvswitch-repo
root@bridge:/tmp# ./install-dvswitch-repo
The Repository file already exists, exiting
root@bridge:/tmp#  apt-get update
Get:1 stretch InRelease [4,806 B]
Err:1 stretch InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 72147EC1E788D4C3
Hit:2 buster InRelease
Hit:3 buster/updates InRelease
Hit:4 buster-updates InRelease
Hit:5 buster-backports InRelease
M: 2020-12-13 23:35:01.060 No repeaters linked
Reading package lists... Done
W: GPG error: stretch InRelease: The followin                                                                             g signatures couldn't be verified because the public key is not available: NO_PU                                                                             BKEY 72147EC1E788D4C3
E: The repository ' stretch InRelease' is not                                                                              signed.
N: Updating from such a repository can't be done securely, and is therefore disa                                                                             bled by default.
N: See apt-secure(8) manpage for repository creation and user configuration deta                                                                             ils.

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