The Dangers of WordPress Multi-Site

A couple of months ago we started work on a multi site wordpress install. Everything was working smoothly. We pushed the codebase up to our staging site with no dramas.

Now a couple of months down the track a funny thing has happened. Multi site is no longer working. Suddenly we can no longer access the sub-domain. No one was sure exactly when it happened, and so it was hard to pinpoint exactly what had happened to cause it to break.

We store backups of all our databases, and as such had a working version of the database.

Now came the ardious task of tralling through data trying to find exactly what was causing the problem.

Process of Elimination 1

  1. Replace each table in the good db with its corrosponding table from the corrupted db.
  2. Test to see when multi site breaks.

Ok Sweet, its the wp-options table.

Process of Elimination 2

  1. Replace each field of the good table with is corrosponding field in the corrupted table.
  2. Test to see when multi site breaks.



But I looked through all the plugins and we use them on all our wordpress sites. Only, this isnt a normal wordpress site, its multi site.

And the culprit… Root Relative Urls

A WordPress plugin that converts all URL formats to root-relative URLs to enable seamless transitioning between staging/production host environments and debugging/testing from mobile devices, without the use of hackish tactics like textual find-replace strategies or risky hosts/NAT spoofing strategies.[1]

What to take away from this

  1. WordPress multi site is very powerful, but must be used carfully.
  2. If something goes wrong, your first step should be to disable all plugins, and then incrementally turn them back on to see if this is the cause of the problem.
  3. Root Relative URL’s does not work out of the box for wordpress multisite.

References: 1.

  • Phil McCrackin

    AARGH! I swear sometimes it’s like wordpress actively works against you. I’ve tried turning all my plugins off but I still can’t get the admin area to work correctly with multi-site enabled. Any other ideas where to start looking.

  • Seymor Budtz

    Thanks for the tips. I was hoping multi-site was going to be pretty straight forward right out of the box, but alas :(

    It’s a shame root relative urls causes the problem as it’s such a handy plugin to use when trying to manage a development and live site.

    Do you think the ability to have the one wp install for multiple seperate domains is something they’re likely to put in?

    • Kalki Rose

      Here is a short example on how to set up one WordPress install for multiple separate domains.

      • Mike Hunt

        Hi, very interesting… I have one question: Are multiple sites using multiple databases or they are all connected to one wp database?

        • Kalki Rose

          The benefit of using WordPress multi-site is that they all run off a single database.

  • Enganar Búrrocaralho

    i has install’ed wordpress-multisite but on the 2nd site the sytles css is not working! can u help pleaseee?

    • Kalki Rose

      Could you supply some more information about what you are trying to achieve, and what you have done so far

  • Missure Popadich

    Excuse me,

    Thank you, I was lost so.

    I ave “root relative urls’ disabled already and nothing still.

    Do you have suggestions???!!

    • Kalki Rose

      Could you supply some more information about what you are trying to achieve, and what you have done so far.

  • Holden MacGroin

    It seems that Domain Mapping plugin is unsupported anymore. Are there any alternatives? Is it possible to setup domains manually using functions.php?


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