Running the command apt-get update or sudo apt-get update on a circleci/classic:201808-01 machine causes the following error:
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://dl.google.com/linux/chrome/deb stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6494C6D6997C215E
W: The repository 'https://packagecloud.io/circleci/trusty/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6494C6D6997C215E
W: Some index files failed to download. They have been ignored, or old ones used instead.
E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)
E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?
Exited with code 100
The CircleCI packagecloud repository is a warning that can be ignored for now (i.e. it does not cause the subsequent 100 exit code, but being unable to get the Linux Chrome key does).
In the meantime this issue can be mitigated by manually updating the key:
wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
As seen here: https://askubuntu.com/questions/943146/apt-update-error-an-error-occurred-during-the-signature-verification-chrome
This issue did not occur last week when I ran the exact same commands on the exact same machines. So it seems to be a new bug introduced within the last 8 days (when I last ran this step successfully).
Thanks for taking the time to reply