user14570: I changed the source code of bitcoin and I ran it. However, it gives the following error:
chainparams.cpp:140: CMainParams::CMainParams(): Assertion `hashGenesisBlock == uint256("0xxx")' failed.

Aborted (core dumped)
It also does not create .altcoin folder in home folder, so I cannot see debug.log. Why is this so?

user24601: The latest bitcoin source doesn't output any debug log in chainparams.cpp. 
You can, 

Use GenesisH0 to find your Genesis block hash.
make && sudo make install
Run it again, then you will see debug.log within your bitcoin folder


14570: <p>I changed the source code of bitcoin and I ran it. However, it gives the following error:</p>

<pre><code>chainparams.cpp:140: CMainParams::CMainParams(): Assertion `hashGenesisBlock == uint256("0xxx")' failed.
</code></pre>

<p>Aborted (core dumped)</p>

<p>It also does not create .altcoin folder in home folder, so I cannot see debug.log. Why is this so?</p>
 24601: <p>The latest bitcoin source doesn't output any debug log in chainparams.cpp. <br>
You can, <br></p>

<ol>
<li>Use <a href="https://github.com/lhartikk/GenesisH0" rel="nofollow">GenesisH0</a> to find your Genesis block hash.</li>
<li>make &amp;&amp; sudo make install</li>
<li>Run it again, then you will see debug.log within your bitcoin folder</li>
</ol>
