My cluster disappeared, but data is still there

Question

I was tasked with recovering data from an old, unmaintaned server, where its main purpose application was no longer working. Basically just want to get a postgres db dump before burning the server to the ground.

I ssh into the instance, but cannot access the database.

psql: FATAL:  database "foobar" does not exist

That's weird. I do pg_lscluster

Version Cluster   Port Status Owner    Data directory                     Log file
9.1     main      5433 online postgres /var/lib/postgresql/9.1/main       /var/log/postgresql/postgresql-9.1-main.log

Okay, something is running. I check the data dir ls /var/lib/postgresql/

8.4  9.1

Huh, okay then. looking at the contents of the two dirs, it is pretty clear that all of the data is in the 8.4 folder, and the 9.1, I can see only holds default data, when I look using psql for the running cluster.

So somehow the cluster that ran 8.4 was removed. No idea why or how (I'm not the only one with access to the server, but I cannot find anything supicious in bash history).

So how would I go about restoring access to the data, so I can pull out a dump?

Answer 1

Alright, I managed to solve it.

I tried to create the cluser

pg_createcluster 8.4 main

It complained that 8.4 was not an installed version. Alright then, this confirms my suspicion, that at some point postgres was upgraded to the latest version in the debian repos, and the data left behind.

So I went to reinstall 8.4 (Remember to backup your data dir, if you want to follow these steps. Don't hold me accountable for any dataloss)

sudo touch /etc/apt/sources.list.d/pgdg.list
sudo echo "deb http://apt.postgresql.org/pub/repos/apt/ wheezy-pgdg main" | sudo tee /etc/apt/sources.list.d/pgdg.list
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
sudo apt-get update
sudo apt-get install postgresql-8.4
pg_lsclusters 

The output of pg_lsclusters showed that the 8.4 main cluster was created during the installation. I was afraid that it would have nuked the data dir with a fresh installation, but it didn't. Running psql revealed all the old data was still there