Grafana Repository Issue (2025 Version)

What’s Going On?

The repository’s key (fingerprint B53AE77BADB630A683046005963FA27710458545) expired on 2025‑08‑23.
This expired key causes the InRelease file signature to be invalid, resulting in the EXPKEYSIG error you're seeing.
This isn't a local issue—Grafana's key on their servers needs a replacement - https://apt.grafana.com/.

Grafana has already rotated and extended the key, so you just need to refresh it on your system:

# Remove old expired Grafana key (if present)
sudo apt-key del B53AE77BADB630A683046005963FA27710458545 2>/dev/null || true
sudo apt-key del 4E40DDF6D76E284A4A6780E48C8C34C524098CB6 2>/dev/null || true
sudo apt-key del 0E22EB88E39E12277A7760AE9E439B102CF3C0C6 2>/dev/null || true

# Create keyring directory
sudo mkdir -p /etc/apt/keyrings/

# Download and install the refreshed Grafana key
wget -q -O - https://apt.grafana.com/gpg.key | gpg --dearmor | sudo tee /etc/apt/keyrings/grafana.gpg > /dev/null

# Update Grafana repo definition to use new keyring
echo "deb [signed-by=/etc/apt/keyrings/grafana.gpg] https://apt.grafana.com stable main" | sudo tee /etc/apt/sources.list.d/grafana.list

# Refresh package lists
sudo apt-get update

# Upgrade Grafana (and other packages if available)
sudo apt-get upgrade

This will:

Clean out any old/expired keys.
Import the new extended key.
Ensure your Grafana repo uses /etc/apt/keyrings/grafana.gpg going forward.

✅ Why This Works

The error was caused because your system still had the old Grafana key cached, which expired on 2025-08-23.
On 2025-08-22, Grafana extended the new key (B53AE77BADB630A683046005963FA27710458545) for two more years.
By re-importing it, you’re telling apt to trust the updated key, and the signature verification will pass again.