I am trying to create a site where any logged-in user is redirected to a page that is specific for that user, when the user logs in.
Suppose that U1, U2, U3 are three users on that site. U1's home page should be http://www.example.com/u1; if U1 created any link, the link should be displayed on http://www.example.com/u1, not on http://www.example.com/u2, or http://www.example.com/u3.
I also want different admin panel for each user logging in.
You can do this with a combination of the themekey module and the login destination module. For both, you would start by creating specific user roles for the your three user types, ex
Then setup these two modules and have all users with userrole1 redirect to a specific page after logging in:
The Login Destination module allows you to customize the destination that a user is redirected to after logging in, registering to the site (7.x), using a one-time login link or logging out (7.x). The destination can be an internal page or an external URL. It is possible to specify certain conditions like referring pages or user roles and make the destination depend upon them.
And then use themekey to switch the theme / output based on the specific user role:
ThemeKey allows you to define simple or sophisticated theme-switching rules which allow automatic selection of a theme depending on current path, taxonomy terms, language, node-type, and many, many other properties.
Aah I get you now reading from the comments. The thing with drupal is to make a module work for you. check out the following two modules: the Homebox, and the Rules modules. They could be a guiding light to what you are looking for.
By default on login drupal redirects to http://example.com/user. Using rules you can customise where the user is directed and that is where homebox comes in handy. My solution would be to create a role and then use a finer grained blocks tool like Boxes. Depending on my business use case I will then build and allow users to do what they want. You could also use blocks although the permissions will not be so fine grained. Be careful however that modules don't get into the way of what you want. Customize stuff and make it work for you.
The easiest way is using the Virtual sites module.
Virtual Sites offers almost the same (and more) functionality as the Drupal multi-site feature without the need for the complicated setup of that feature. Depending on conditions (e.g. requested url or user role) handled by the Condition(s) module (bundled with Virtual Sites starting with the 7.x version), you can override theme, site information, menus and more to virtually present the visitor with a different website.
