Can't install elementary-tweaks on Juno

Question

I'm trying to install elementary-tweaks on Juno but adding the ppa is causing an error. Here is my console output...

Err:7 http://ppa.launchpad.net/philip.scott/elementary-tweaks/ubuntu bionic InRelease                                                                  
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C1D89326B1C71AB9
Get:10 http://packages.elementary.io/appcenter bionic/main amd64 DEP-11 Metadata [88.5 kB]
Hit:11 https://packages.lunarg.com/vulkan/1.1.85 bionic InRelease 
Reading package lists... Done                                           
W: GPG error: http://ppa.launchpad.net/philip.scott/elementary-tweaks/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C1D89326B1C71AB9
E: The repository 'http://ppa.launchpad.net/philip.scott/elementary-tweaks/ubuntu bionic InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Anyone know how I go about fixing this ? Thank you.

Answer 1

Follow this steps

Open a terminal, then write and execute (by pressing ENTER) this commands, one at a time:

• sudo apt install software-properties-common

  • will ask your password

• sudo add-apt-repository ppa:philip.scott/elementary-tweaks

  • will ask you press ENTER to confirm the installation of the PPA

  • (newer version of add-apt-repository runs apt update after automatically. In case it didn't, just run sudo apt update yourself)

• sudo apt install elementary-tweaks

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Description of your problem:

You didn't (don't) have the gpg key, with add-apt-repository you get it. And installing software-properties-common provides that command.

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I'm curious, which instructions did you follow to install elementary-tweaks?