Ubuntu – How to get chmod (octal) permissions of the folder in the terminal

By default, Apache on Ubuntu runs as www-data.

Let's assume your folder is located in /var/www/mysite.

You can do this:

chown -R www-data:www-data /var/www/mysite
chmod -R og-r /var/www/mysite

After doing this, www-data (the Web server) will have full access to the site's files, while other non-root users will have no access at all.

If you wish to allow select users to access the site, you can make the folder group-readable and add those users to the group www-data.

I'm going to address two parts of your question: java installation and folder creation.

Java installation

We already have a question about that: How can I install Sun/Oracle's proprietary Java JDK 6/7/8 or JRE?.All of the necessary commands are there, and I strongly suggest you read their manual pages with man COMMAND in terminal.

There's also open-source version of Java, Open JDK. Installation of that is somewhat simpler

sudo apt-get install openjdk-7-jre openjdk-7-jdk icedtea-7-plugin

That's pretty much it - apt-get will take care of everything. When you install some package with apt-get or dpkg there should be preinstall and postinstall scripts that come along with the package, and run automatically to set up whatever program you're getting.

Folder Creation

Folder ( in linux terminology - directory ) creation, just like file creation, depends on the permissions. If a folder has the following permissions,

drwxr-xr-x 15 testuser  testuser   4096 Nov 22 12:34 testuser/

that means the owner of that folder testuser can read-write-execute stuff there (first rwx), and group testuser can only read and execute stuff there - that's the r-x part, and final r-x part means read execute for any other groups or users.

/usr folder is owned by root user, so only root can write there, that means create files or folder. Hence for that you need sudo to gain root privileges temporarily.