Publishes a new tutorial about PostgreSQL 11 migration on Debian

_posts/2019-11-15-from-stretch-to-buster-how-to-upgrade-a-9-6-postgresql-cluster-to-11.md

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+---
+title: "From Stretch to Buster : How to upgrade a 9.6 PostgreSQL cluster to 11 ?"
+date: 2019-11-15
+url: from-stretch-to-buster-how-to-upgrade-a-9-6-postgresql-cluster-to-11
+layout: post
+category: Tutorials
+image: /img/blog/from-stretch-to-buster-how-to-upgrade-a-9-6-postgresql-cluster-to-11.png
+description: "A step-by-step tutorial for a not-so-guided Debian migration"
+---
+
+[![A missing blog post image](/img/blog/from-stretch-to-buster-how-to-upgrade-a-9-6-postgresql-cluster-to-11.png)](/img/blog/from-stretch-to-buster-how-to-upgrade-a-9-6-postgresql-cluster-to-11.png)
+
+### Introduction
+
+Here we are, Debian Buster (10) has been out as the new _stable_ release for 4 months now, so it's definitely time to upgrade your servers !
+
+As long as PHP 7.3 (:relieved:), there are plenty of new awesome stuffs to take in consideration.  
+The target of this short post is PostgreSQL.
+
+Back in the "past", Debian Stretch (9.9) proposed the version 9.6 of the RDBMS, whereas Buster (10.X) now allows you to enjoy the 11th major version.
+
+But there is a caveat : this upgrade is supposed to be as straightforward as the distribution itself, but IMHO, it's not.  
+So here is one more step-by-step guide.
+
+### System upgrade
+
+{% highlight bash %}
+# Let's upgrade to the latest Stretch
+apt update && apt upgrade -y
+
+# Major upgrade to Buster
+sed -i 's/stretch/buster/g' /etc/apt/sources.list
+apt update && apt dist-upgrade
+{% endhighlight %}
+
+### A first issue
+
+So at this step, you should have a running PostgreSQL 9.6 cluster... as before then.  
+Pretty confusing, huh ? That's not the all of it.
+
+[Due to a minor update of the glibc changing system's locales](https://www.debian.org/releases/buster/amd64/release-notes/ch-information.en.html#postgresql-reindex), you'll need to re-index all your databases entries.
+
+So let's do it :
+
+{% highlight bash %}
+su - postgres -c 'reindexdb --all'
+{% endhighlight %}
+
+### Migration to PostgreSQL 11
+
+What is even more confusing is that the upgrade process has installed on your system the `postgresql-11` package, initialized with an empty (useless) `main` cluster.  
+As upgrading to 11 is not a meaningless operation, it looks like maintainers preferred letting the 9.6 version available on Buster, including once the upgrade is done.
+
+You can actually check your setup this way :
+
+{% highlight bash %}
+su - postgres -c 'pg_lsclusters'
+
+# or this way :
+systemctl status postgresql.service
+
+systemctl status postgresql@9.6-main.service
+systemctl status postgresql@11-main.service
+{% endhighlight %}
+
+So let's migrate then !
+
+**Before anything else here, I'd advise you to transfer your specific PostgreSQL configuration from `/etc/postgresql/9.6/*` to `/etc/postgresql/11/*`.**
+
+Once it's done :
+
+{% highlight bash %}
+# We first delete the new empty default `main` cluster
+su - postgres -c 'pg_dropcluster --stop 11 main'
+
+# Now we may effectively upgrade from 9.6 to 11 this way
+su - postgres -c 'pg_upgradecluster 9.6 main'
+{% endhighlight %}
+
+PS : If your setup runs multiple clusters, don't forget to upgrade them all !
+
+### Final cleanup
+
+When you have verified that everything works well against v11 cluster(s), you may safely remove the old (outdated) PostgreSQL 9.6 packages :
+
+{% highlight bash %}
+su - postgres -c 'pg_dropcluster --stop 9.6 main'
+
+apt autoremove postgresql-9.6
+apt autoclean
+{% endhighlight %}
+
+### Conclusion
+
+Even if PostgreSQL 9.6 [is still currently supported](https://www.postgresql.org/support/versioning/), this major version [has to be considered outdated](https://tracker.debian.org/pkg/postgresql-9.6) from a Debian point of view.
+
+Hope it was clear enough and that you'll figure something out.  
+If you encounter any issue, please let a comment below, I'll do my best to review them.
+
+Bye :wave: