When working with Ubuntu or other Debian-based systems, encountering errors like “signature verification failed” or “Release file is not valid yet” during apt update can be quite disruptive.
These errors prevent you from updating your system and installing new software, which can be a significant roadblock. I’ve dealt with these issues many times, and I’ll share my practical experience to help you solve them effectively.
Understanding the Problem
The Advanced Package Tool (APT) is a powerful package management system used by Debian and its derivatives, like Ubuntu. It handles the installation, removal, and updating of software packages. To ensure the integrity and authenticity of the packages, APT uses GPG (GNU Privacy Guard) signatures.
When you run sudo apt update, APT does the following:
- Fetches the Release File: APT downloads a
Releasefile from each repository listed in your/etc/apt/sources.listfile and any files in the/etc/apt/sources.list.d/directory. The Release file contains metadata about the packages available in the repository, including their checksums and digital signatures. - Verifies the Signature: The
Releasefile is signed with the repository maintainer’s GPG private key. APT uses the corresponding public key (stored on your system) to verify the signature. This ensures that the Release file hasn’t been tampered with. - Checks Timestamps: The
Releasefile contains timestamps (Valid-Until and Date fields). APT checks these timestamps to ensure the file is current. - Fetches Package Lists: The package index files themselves (e.g., Packages, Sources, Translation-*) are not individually signed. Their integrity is protected by the hashes present in the Release file.
Common Causes
- Outdated or Corrupted Keys: The GPG keys used to verify the repository signatures might be outdated, corrupted, or missing from your system’s keyring.
- Repository Configuration Issues: There might be problems with the repository URLs in your sources list, such as typos, incorrect mirror addresses, or disabled repositories.
- System Time Issues: The error “Release file is not valid yet” often indicates that your system’s date and time are incorrect. APT checks the validity period of the Release file, and if your system time is behind, it might think the file is not yet valid.
- Proxy or Network Problems: If you’re behind a proxy server or have network connectivity issues, APT might fail to download the Release files or their signatures.
- Partial Downloads or Corrupted Cache: Sometimes, due to interruptions or errors during download, the local cache of package lists might become corrupted.
Read: How to use the APT command on Ubuntu/Debian Linux systems
Solutions
1. Fix System’s Date and Time
Ensure your system’s date and time are accurate. An incorrect system clock can cause APT to reject Release files as “not valid yet.”
You can synchronize your system time using the timedatectl command:
sudo timedatectl set-ntp true Tip: This command enables Network Time Protocol (NTP) synchronization, which automatically keeps your system clock accurate. It’s important, particularly for servers, to ensure the time is synchronized with a reliable source to prevent various issues, not just with APT but with many other time-sensitive operations.
To check your current system time settings:
timedatectl status 2. Update and Refresh Your Keyring
Sometimes, the keyring containing the GPG keys for the repositories might be outdated or corrupted.
Update specific keyrings
Reinstall the keyring packages for the repositories you use:
sudo apt-get install --reinstall ubuntu-keyring
sudo apt-get install --reinstall debian-keyring For third-party repositories (like Google Chrome), reinstall the corresponding package:
sudo apt-get install --reinstall google-chrome-stable Manually import keys
If the above doesn’t fix the issue, you can manually import keys. First, identify the key ID from the error message. It usually appears in a format like “NO_PUBKEY ABCD1234”.
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys KEY_ID
# Replace KEY_ID with the actual key ID from the error message Alternatively, you can use GPG directly:
gpg --keyserver keyserver.ubuntu.com --recv-keys KEY_ID
gpg --export --armor KEY_ID | sudo apt-key add - Note: The apt-key command is deprecated in newer versions of Ubuntu. For a more future-proof solution, add repository keys to /etc/apt/trusted.gpg.d/ instead.
3. Clean and Update the APT Cache
Clearing the APT cache can resolve issues caused by corrupted or outdated package lists:
sudo apt clean sudo rm -rf /var/lib/apt/lists var wpcf7 = {"apiSettings":{"root":"https:\/\/net2.com\/wp-json\/contact-form-7\/v1","namespace":"contact-form-7\/v1"},"cached":"1"};