Solved: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY

Recently, I faced this error when i update the all application in my Raspberry Pi using:

sudo apt-get upgrade

and the error was:

W: http://deb.debian.org/debian/dists/bullseye-updates/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/influxdb.gpg are ignored as the file has an unsupported filetype.
W: GPG error: https://repos.influxdata.com/debian bullseye InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D8FF8E1F7DF8B07E

To resolve the issue, I tried the following steps:

1. Import the InfluxDB repository public key:

wget -qO- https://repos.influxdata.com/influxdb.key | sudo apt-key add -

2. Add the InfluxDB repository to the list of trusted repositories:

echo "deb https://repos.influxdata.com/debian bullseye stable" | sudo tee /etc/apt/sources.list.d/influxdb.list

3. Update the package list:

sudo apt-get update

However, I received the same problem but I could solve this issue using the following steps:

1. Remove the existing keyring file:

sudo rm /etc/apt/trusted.gpg.d/influxdb.gpg

2. Download a new keyring file using the wget command:

wget https://repos.influxdata.com/influxdb.key

3. Import the new keyring file into the trusted.gpg.d directory:

sudo mv influxdb.key /etc/apt/trusted.gpg.d/

4. Update the package list:

sudo apt-get update

I hope this solution solves your problem as well.