Tomcat server.xml docbase invalid

Question

Problem

After installing tomcat following https://www.digitalocean.com/community/tutorials/how-to-install-apache-tomcat-8-on-ubuntu-14-04 (Where $CATALINA_HOME=/opt/tomcat)

I added

<Context path="" docBase="/root/mysite/site" debug="0" reloadable="true" />

inside the tag

<Host name="localhost"  appBase="webapps"
            unpackWARs="true" autoDeploy="true">

in opt/tomcat/conf/server.xml

However tomcat says:

Caused by: java.lang.IllegalArgumentException: The main resource set specified [/root/mysite/site] is not valid

I've been struggling the whole afternoon. The setup process was from my notes which was recorded just after setting tomcat up on another machine.

My Experiments:

1. doubled checked that /root/mysite/site is good. All folders are 755.

2. changed docBase to docBase="/opt/tomcat/webapps/ROOT" . Tomcat startup successful.

3. move /root/mysite/site to /opt/tomcat/webapps/ROOT . Tomcat startup successful.

Answer 1

The /root folder is 700. And the guide instructed me to create tomcat's own user & group. My experiment 1 is nonsense. What a horrible mistake!