After an upgrade from Ubuntu Server 14.04 to 16.04 I had to also upgrade my Postgres clusters from 9.3 to 9.5. The normal way to do that is to first drop the (empty) 9.5 cluster that the upgrade created:

# pg_dropcluster 9.5 main

and then to upgrade the old 9.3 cluster to 9.5:

# pg_upgradecluster 9.3 main

This however results in an error:

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = "en_US.UTF-8",
LC_ALL = (unset),
LC_PAPER = "nl_NL.UTF-8",
LC_ADDRESS = "nl_NL.UTF-8",
LC_MONETARY = "nl_NL.UTF-8",
LC_NUMERIC = "nl_NL.UTF-8",
LC_TELEPHONE = "nl_NL.UTF-8",
LC_IDENTIFICATION = "nl_NL.UTF-8",
LC_MEASUREMENT = "nl_NL.UTF-8",
LC_TIME = "nl_NL.UTF-8",
LC_NAME = "nl_NL.UTF-8",
LANG = "en_US.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
Error: The locale requested by the environment is invalid.
Error: Could not create target cluster

This means I could not upgrade to Postgres 9.5.

I checked all locale settings:

• the en_US.UTF-8 locale exists and is properly generated as checked with locale -a (it shows en_US.utf8 in its list)
• The file /etc/environment contains LC_ALL=en_US.UTF-8 and LANG=en_US.UTF-8
• /etc/default/locale contains the same setting for LANG, LANGUAGE and LC_ALL
• I can start Perl without any issue using "perl -e exit"

The error message is generated from the pg_createcluster script which is called from pg_updatecluster. But running pg_createcluster from the command line works just fine, without any issue.

Workaround for the issue:

I used the following workaround to at least get the conversion to work. I edited the /usr/bin/pg_upgradecluster script, as follows:

• Find the code where it calls pg_createcluster by looking for the comment "create new cluster"
• That code consists of a series of "push" statements, ending in the suspicious line: delete $ENV{'LC_ALL'}
• Notice that this LC_ALL is exactly the variable that is unset in the error message.
• Comment out that delete comment by adding a '#' before it, then save.

This at least circumvents this problem and lets you run the upgrade.

My question: is this a bug in the pg_upgradecluster script, or is something else awry on my system?

had the same problem on an ubuntu 16.04 server. what helped in my case was to generate all the locales that appear in your listing of $ locale:

$ sudo locale-gen "en_US.UTF-8"
$ sudo locale-gen "nl_NL.UTF-8"

good luck!