user78203: I am following the installation steps to setup a bitcoin node, at the steps "Download the blockchain" that required Bitcoin Core GUI which is not able to run on the testing Ubuntu Server without GUI. 
The guideline I am following is https://bitcoin.org/en/full-node#ubuntu-1610. At the Ubuntu Installation, under Bitcoin Core GUI.

Is there any command to trigger the download without GUI? Thank you very much.

user48884: In the very same guide you linked, follow the instructions for the Bitcoin daemon.

I tried to start the daemon and hope it will download the data but it seems nothing change on H.D. usage so I am guessing it is not downloading. Am I correct?

No, you are not correct. You should check the status of bitcoind itself by using bitcoin-cli to send commands to it. You can use getblockchaininfo to know whether it is actually syncing by calling it twice. If it is syncing, then it will report a different block height and best block hash on the second call.

78203: <p>I am following the installation steps to setup a bitcoin node, at the steps "Download the blockchain" that required Bitcoin Core GUI which is not able to run on the testing Ubuntu Server without GUI. </p>

<p>The guideline I am following is <a href="https://bitcoin.org/en/full-node#ubuntu-1610" rel="nofollow noreferrer">https://bitcoin.org/en/full-node#ubuntu-1610</a>. At the Ubuntu Installation, under Bitcoin Core GUI.
<a href="https://i.stack.imgur.com/gHGEF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gHGEF.png" alt="enter image description here"></a></p>

<p>Is there any command to trigger the download without GUI? Thank you very much.</p>
 48884: <p>In the very same guide you linked, follow the instructions for the <a href="https://bitcoin.org/en/full-node#ubuntu-daemon" rel="nofollow noreferrer">Bitcoin daemon</a>.</p>

<blockquote>
  <p>I tried to start the daemon and hope it will download the data but it seems nothing change on H.D. usage so I am guessing it is not downloading. Am I correct?</p>
</blockquote>

<p>No, you are not correct. You should check the status of <code>bitcoind</code> itself by using <code>bitcoin-cli</code> to send commands to it. You can use <code>getblockchaininfo</code> to know whether it is actually syncing by calling it twice. If it is syncing, then it will report a different block height and best block hash on the second call.</p>
