Some more ways to go if you want a Single Sign On Solution using Drupal:

As explained in the article , the method of sharing database tables between several drupal sites enables people to use the same username/password combinations on all sites. It does however not automatically log you in at all subsites. Besides the singlesignon and fierce_sso modules, the Drupal Multisite Login Module (http://drupal.org/project/multisite_login) will also log you in automatically.

If you are looking for solution to integrating several non-Drupal sites into a single-signon network, then the Drupal Modules supporting CAS, CoSign or Sebboleth authentication might be an option for you. Note however that these options will usually not run on the usual cheap PHP&MySQL hosting services.

If you don't need the Single-Signon-Features (that log you in automatically), but if all you need is to have the same username/password combinations on a number of sites, then consider using OpenID (which is very well integrated into Drupal) or LDAP authentication.

...works well. But the following should be considered, if the database is converted from an existing site which contains already nodes, users, etc.:

Table 'sequences' (new: 'shared_sequences') contains entries in the form
name = "table"_"id",
id = counter / max existing id of "id" in table "table".
These counters tell Drupal how to generate new content (nodes, comments, users, etc.)

You must convert the name entries to the newly renamed table names:
name = "new-table"_"id"

Otherwise Drupal will create these entries itself when necessary, but starts counting from the beginning. Soon it will collide with id numbers of existing content.

Example:
users_uid -> shared_users_uid
comments_cid -> site_1_comments_cid
files_fid -> site_1_files_fid
menu_mid -> site_1_menu_mid
node_nid -> site_1_node_nid
node_revisions_vid -> site_1_node_revisions_vid
term_data_tid -> site_1_term_data_tid
vocabulary_vid -> site_1_vocabulary_vid

Depending on your installed modules there might be other entries which must be changed, too.

In my opinion, the 'sessions' table should not be shared! Otherwise users logged in at one site are shown at all sites as logged in. Moreover, a certain user logged in at two sites is shown twice at all sites. Keeping the sessions table individual prevents this. Are there other arguments to share the table?

In order to make the subscriptions module work for two sites with shared users

I shared the subscriptions_user table while each site has their own versions of the other three subscriptions tables.

It all works fine.

All the best,

JanPieter

Looking for a solution based on the following criteria.

1.1 - www.example.com will be a portal page that links to Canada (www.example.ca) and US (www.example.us).

1.2 - These pages will share the same database but not the same users tables. I believe if I don't include 'users' => 'shared_' in the settings.php for both subs it should create sub users tables. Please advise if this is the proper way of handling.

The following is beyond this topic but maybe it has some importance in helping me make a better decision on how to approach this project.

- Each sub-site of the multi-site will have different users that will see different prices in an Ubercart shopping cart.

I would appreciate any feedback, advice or strategies you can propose.

Cheers,
------------------------------------------
Solutions for interactive design™
www.ss-interactive.com

Dan

In the directory /var/www, enter the following commands:

ln -s drupal site_1
ln -s drupal site_2

Where exactly do I include these commands? Is there a file I should open in the directory /var/www?

Thanks
------------------------------------------
Solutions for interactive design™
www.ss-interactive.com

Dan

Drupal 6.8/Linux/PHP5.2/MySQL 5.0

I had the same problem as one of the previous commentors(djbdjb-all of the table exists warnings) and the install wouldn't finish but I found a solution so I will share it here.

I did all of the above except that I did not use the shared_ prefix for both of my sites, in the site1 settings.php I used shared_, then in site2 I used shared1_. This effectively created 2 sets of shared tables (shared_ and shared1_) After I finished the installs I went into the database and executed the following query to move the user that was setup in site2 over to the shared_users table from the shared1_users table:

INSERT INTO `shared_users` (name,pass,mail,mode,sort,threshold,theme,signature,created,access,login,`status`,language,picture,init,data)SELECT name,pass,mail,mode,sort,threshold,theme,signature,created,access,login,`status`,language,picture,init,data FROM `shared1_users` WHERE ( `shared1_users`.`uid` = 1 )

Now, the next issue was that the user created in site2 was no longer the default admin for the site. If you look in the menu_router table for site2 you can pretty much understand how the user id is used to grant the rights but I didn't want to have to change a text field in dozens of rows in the menu_router table for each site so I created a role named Administrator and assigned the site2 user to it. Since the roles table is one of the shared tables it was in every site BUT, I had to log in to both sites as the adminstrator of site1(the first installed site) and set up all permissions for the role. Once I did that it saved all of the site2 user's information correctly in the site2_menu_router table and gave him full perms on site2. I did take it 1 step further after the fact by creating a separate administrator role for each site so I didn't have to give the admin of 1 sight administrator rights to another site.

So now I have a "master" user which was the initial user setup in the first site install and then regular admins for each site. I haven't done any more configuring yet so I don't know if there will be other issues but I doubt it because I am only sharing 4 tables and they are all about users and perms.

I have cpanel hosting and also an access to SSH. My drupal is installed in the root directory and not in the "Drupal" folder. It is drupal 6 and not 5.

I was trying to install multisite with shared login at site1.example.com according to the guide above but couldn't achieve it. Actually I don't know how to run SSH commands. I can login at SSH but I couldn't go to var/www because no such directory exists there. My drupal is installed in home/user/public_html/ and not in var/www which is not supported by my host. However when I try to open home/user/public_html in SSH using 'open' command, it says permission denied. And I am no good at SSH.

My goal is to achieve shared login among all the multi sites including the parent site at www.example.com. If one person registers at www.example.com, he/she can login to other sites also with same login credentials and vice a versa. I can do multi site as guided at http://drupal.org/node/257661#comment-841411 but couldn't achieve shared login.

Please guide me on achieving the shared login in multisite. Your help will be appreciated.

I just setup my website and it works.

A) For the above procedure (and comments), SKIP modify part 2.2.2 when setup site 2, until you have finish setup your database (in part 4):
$db_prefix = array(
'default' => 'site_2_',
'users' => 'shared_',
'sessions' => 'shared_',
'role' => 'shared_',
'authmap' => 'shared_',
'sequences' => 'shared_',
'profile_fields' => 'shared_',
'profile_values' => 'shared_',
'users_roles' => 'shared_',
);

The reason is, it will return a lot of errors on "duplicate table already exists" during setup of site 2. Even worst, it just create some tables and then terminate the script in the middle. In this case, you need to drop the tables to retry (or you may manually create the remaining tables).

My advice is, change the script to:
$db_prefix = array(
'default' => 'site_2_',
);

Let Drupal creates duplicate tables in the database first, then modify the script back to
$db_prefix = array(
'default' => 'site_2_',
'users' => 'shared_',
'sessions' => 'shared_',
'role' => 'shared_',
'authmap' => 'shared_',
'sequences' => 'shared_',
'profile_fields' => 'shared_',
'profile_values' => 'shared_',
'users_roles' => 'shared_',
);

Done! You may or may not delete the 8 duplicate tables (site_2_users, site_2_sessions, ...).

B) For multisites single DB, there is no need to install additional module to login both sites. Just uncomment the line and change to your domain name:
$cookie_domain = 'www.yourdomain.com';
in the subdomain's settings.php file.

Users can login multisites with one username/password with single login. Once logout, all sites are logout.

I'm working on a system to split a site in order to achieve a performance gain in sites that use a lot of modules (80 or more). Rather than share a small number of tables as shown in this example I want to share as many tables as possible but separate out system, blocks, menu, caches, node_access and sufficient tables to reduce the module load on each subdomain so that each subdomain carries a subset (about 40 or less) of the modules used in the site overall rather than all of them. For instance I want to have:

store.example.com - ecommerce
jobs.example.com - jobs section
www.example.com - has front page and main section

I have set up so that the following tables are not shared:

menu
blocks
blocks_roles
boxes
all caches
variable
system
node_access

Having done that I had to find a way to share the main menu systems across the subdomains so that the user ostensibly remains on the same site. For that I wrote a module that propagates menu systems selected from the master domain to the subdomains. This module can be found here: http://webdev.passingphase.co.nz/?q=project/site-splitter. Currently it works well, only doesn't always retain the menu in the active block depending on what changes are made to the master menu or the subdomain menu systems.

I've been trying to setup a multisite on my development Linux box where http://localhost/drupal maps to the file /var/www/localhost/htdocs/drupal so that I could setup several sites, one per chapter, of Using Drupal by Byron et. al (a wonderful text, by the way), and your method is the only one I could understand and the only one that actually worked after two solid days of reading all the multisite documentation I could find here.

Thanks!