GPG key problem

Yesterday I ran into this funny problem and thought it’s good to write this down. I was updating a Heroku shiny app, which uses a fantastic Docker Image. And it throws a cute error:

GPG error: focal-cran40/ InRelease: The following signatures were invalid: EXPKEYSIG 51716619E084DAB9 Michael Rutter <>

Sure sounded like the GPG key expired! I then ran into exact same problem in my virtual machine created in Cyverse’s Atmosphere.

The GPG key expired on 2020-10-16, how lucky was I?! Because the Docker image was created, and the key was added pre 2020-10-16, the key is no longer valid! But what should the “new key” be? It turns out that the same key now has a new expiry date in 2027, but I needed to remove the key and re-add the same key. For the Docker image, it has been re-built and pushed into the Dockerhub. All good now.

To check your GPG key:

sudo apt-key list

This is the “offending” GPG key:

pub   rsa2048 2010-10-19 [SCA] [expired: 2020-10-16]
      E298 A3A8 25C0 D65D FD57  CBB6 5171 6619 E084 DAB9
uid           [ expired] Michael Rutter <>

To remove the key:

sudo apt-key del "E298 A3A8 25C0 D65D FD57 CBB6 5171 6619 E084 DAB9"

And then to add it back:

sudo apt-key adv --keyserver --recv-keys E298A3A825C0D65DFD57CBB651716619E084DAB9

Checking the GPG again and this key now expires in 2027-09-30:

pub   rsa2048 2010-10-19 [SCA] [expires: 2027-09-30]
      E298 A3A8 25C0 D65D FD57  CBB6 5171 6619 E084 DAB9
uid           [ unknown] Michael Rutter <>
sub   rsa2048 2010-10-19 [E] [expires: 2027-09-30]

Something something don’t take anything for granted :D