move postgresql 9.4 cluster to new server I have a redmine postgresql folder backup (no dump) from postgresql 9.4
and want to move it to a new server with debian 10 (buster) with postgres 11.

On my debian buster server I tried to get this old database running, so I installed the old postgresql-9.4 there with this tutorial: https://wiki.postgresql.org/wiki/Apt#Quickstart

When I tried to start the old cluster it said: 

$ pg_createcluster 9.4 main --start
Configuring already existing cluster (configuration: /etc/postgresql/9.4/main, data: /var/lib/postgresql/9.4/main, owner: 117:120)
Error: move_conffile: required configuration file /var/lib/postgresql/9.4/main/postgresql.conf does not exist


I managed to start a new cluster2 with this instruction: https://stackoverflow.com/a/48624460/1069083

But that one is empty. My old main cluster contains all my data.

How do I start the old main cluster?
I solved it like this:


I had to restore the old config too in 

/etc/postgresql/9.4/main

Then I could start the old main cluster with

pg_ctlcluster 9.4 main start

Then I had to update redmine:

cd /usr/share/redmine


and start

bundle exec rake db:migrate RAILS_ENV=production

check if redmine is working correctly in your browser, Now you can upgrade postgresql to 11. first dump the database with

sudo -u postgres pg_dumpall &gt; /root/full_dump.sql  

remove postgres 9.4 and install postgres 11, then 

sudo -u postgres psql -d postgres &lt; /root/full_dump.sql
/etc/init.d/postgresql restart

check /var/log/redmine/default/production.log for any errors, for example check in /etc/redmine/default/database.yml if redmine is still trying to connect on port 5433