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I have a former customer who, contrary to my recommendations, has not stayed on top of their WP upgrades. They now need to make the leap from 3.5.1 to 4.1.1 (or whatever is current at the moment). They used a fairly vanilla theme (might have even been Twenty Eleven), and not used too many plugins.

I have found numerous threads (here and elsewhere) that talk about doing this 1 mini-upgrade at a time. Is this really necessary, or can bigger steps be taken? E.g. 3.5.1 -> 3.9, then 3.9 -> 4.0, and then 4.0 -> 4.1.1

Thoughts or experiences are appreciated.

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  • step 1- back up the files and database and mirror it in a test installation. then you can test whatever upgrade process you choose with no risk.
    – Milo
    Commented Feb 27, 2015 at 1:31
  • OK. I have an ancient copy of BackupBuddy that seems to work in this environment, so I'll use that. Thanks! Commented Feb 27, 2015 at 2:25
  • Make sure to turn debug on, some functions was depreciated between 3.5 and 4.1 Commented Feb 27, 2015 at 4:31

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Check out the Codex on Upgrading Across Multiple versions.

Regarding the upgrading steps, it says:

If you plan on upgrading across more than two major releases, please consider upgrading incrementally to avoid potential conflicts and minimize the risks of database damage. For example, if you plan on upgrading from 2.5 to 4.1.1, upgrade to 2.7 first, followed by 2.9, then 3.1, and so on. Essentially, it's okay to skip one release, but never skip TWO when upgrading.

So according to this advice, your upgrade sequence could be:

3.5.1 -> 3.7.x -> 3.9.x -> 4.1.1

I agree with the comments by @Milo and @PieterGoosen; You shouldn't experiment with this on a production install, test this first on your dev install. Deactivate plugins before the upgrades and activate them afterwards, one at a time. Remember to activate the debug log and scan through the debug.log for errors.

Remember to backup everything.

You can find the old releases here.

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  • Thanks, for both the explanation and the link to older versions! Commented Feb 27, 2015 at 21:33
  • You're welcome and good luck with the upgrades ;-)
    – birgire
    Commented Feb 27, 2015 at 21:34

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