May 31, 2019  Now you will need to generate a sha256 checksum for the downloaded ISO a file. Then match it to the SHA256SUM file that you have downloaded from Ubuntu mirrors. Make sure you have placed downloaded file, SHA256SUMS, and SHA256SUMS.gpg in the same directory. Run the following command in the Terminal: $ sha256sum -c SHA256SUMS 2&1 grep OK.

  • Picture 5 How to create GPG key in Linux download this picture HERE. Use the 8-digit User ID to find and enter the following information (replace B852 085C with your own ID): gpg -keyserver -send-key B852085C. The public key will then be registered with the keyserver, where others can find and enter it.
  • How To Create A GPG Key Ubuntu. After entering the passphrase, do some random actions on your computer so that it can generate enough random bytes.


  1. Get the key
  2. Check the ISO

Verifying Ubuntu ISO images assumes basic knowledge of the command-line, checking SHA256 checksums, and using GnuPG. While MD5 checksums are also provided on the server, MD5 is not considered secure and should only be used to check for accidental corruption of a download; it should not be used together with gpg for verification that your download has not been compromised.

The steps are

  1. Download SHA256SUMS and SHA256SUMS.gpg

  2. Get the key used for the signature
  3. Verify the signature
  4. Check the ISO with sha256sum

After verifying the ISO file, you can [BurningIsoHowto burn it to a CD].

Just download the two files from any of the mirrors. Store them in the same directory. For Trusty, the CD image SHA256SUMs can be found at and the Trusty DVDs can be found at If you're using another version of Ubuntu, change '14.04' in those URLs to your version number (e.g. 16.04 for Xenial).

Find out what key was used to issue the signature

By running GnuPG to verify the signature we can find out what key is needed:

The key IDs are 0x46181433FBB75451 (generated in 2004, deprecated) and 0xD94AA3F0EFE21092 (generated in 2012, current). Note that we use GPG's 'long' (64-bit) key IDs, since 'short' (32-bit) key IDs are insecure.

Obtain the public key from the Ubuntu key server

To add the wanted key automatically to your keyring from the Ubuntu keyserver and calculate its trust:

Verify the key fingerprints:

Now when you verify the sums file you'll get a result resembling this:

In this example a 'Good signature' validates the integrity of the given file. The warning message indicates your current GnuPG trust database does not have trust information for that signing key, unless you have actually verified and signed one of the public keys belonging to signers of the Ubuntu CD Image signing key. For more information about the OpenPGP Web of Trust see:

  • Building your web of trust

  • GnuPG trustdb how-to

On hard disk

The file SHA256SUMS contains SHA256 hashes of the ISO images. Run sha256sum on the ISO and compare the result with the relevant line in SHA256SUMS. See this link for more information on SHA256SUMS.

Or doing it automatically with a one line script.


Check again after burning since growisofs adds extra blank bytes increasing file size from 3048179712 (0xB5AF8800) to 3048210432 (0xB5B00000) bytes

While booting

You can also check a disc while you are booting from it. This is useful for testing that your target hardware can properly read all of the disc.

Divide the image size in bytes by 512 to get the size in blocks. Boot from the disc, and when the installer has reached the disk partitioning stage, switch to a shell (alt-2) and run the following command, adding the size of the ISO image in blocks as the argument 'count'.

Other Languages:

Ubuntu Iso Generate Gpg Key For Download

  • Spanish (Espa単ol): ComoVerificarIso

Ubuntu Iso Generate Gpg Key Server

With a bootable Ubuntu USB stick, you can:

  • Install or upgrade Ubuntu
  • Test out the Ubuntu desktop experience without touching your PC configuration
  • Boot into Ubuntu on a borrowed machine or from an internet cafe
  • Use tools installed by default on the USB stick to repair or fix a broken configuration

Creating a bootable Ubuntu USB stick is very simple, especially from Ubuntu itself, and we’re going to cover the process in the next few steps.

Alternatively, we also have tutorials to help you create a bootable USB stick from both Microsoft Windows and Apple macOS.

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