PostgreSQL – How to Restore Database from Database Files

migrationpostgresqlpostgresql-9.1postgresql-9.3

I am running Ubuntu 14.04 with a postgres/postgis setup and in a weak moment removed PostgreSQL 9.1 (seemingly a legacy install from 12.04 from before I upgraded to 14.04), having erroneously convinced myself my current postgis setup relied on 9.3 alone.

That was not the case, and to make matters worse, I removed it while the instance was running, so I headed to the repositories to restore 9.1.

The repositories for Ubuntu don't have PostgreSQL 9.1 for 14.04, so I instead compiled from source so I could run pg_dump or pg_upgrade, which requires binaries from both.

But my issue then was that just because I now had a working version of 9.1 again, that didn't make my databases from earlier visible.

So, as far as I am aware, my database files are intact, but I need to 'hook' them up with the new 9.1 service I installed today. I hope it is trivial, but it has stumped me for hours. Any pointers for where to start with updating the config?

Best Answer

@a_horse_with_no_name is quite right. Because you compiled PostgreSQL from source, the usual tools provided by pg_wrapper like pg_ctlcluster and pg_lsclusters are not available. As a result the PostgreSQL init scripts on Ubuntu won't start your PostgreSQL 9.1 DB.

You could hook your custom binaries into pg_wrapper, but it's not worth the hassle for a one-off.

Assuming your 9.1 data directory is still owned by user postgres and in the default location:

  • sudo -u postgres -i
  • PGPORT=5440 PATH=/path/to/your/9.1_install/bin pg_ctl -D /path/to/your/9.1/db
  • PGPORT=5440 /path/to/9.3/bin/pg_dump -Fc -f mydb.pgdump mydb
  • PGPORT=5440 /path/to/9.3/bin/pg_dumpall --globals-only > my_91_globals.sql

then run my_91_globals.sql against your 9.3 server, or examine it and make any required changes.

Then pg_restore the mydb.pgdump using the pg_restore from 9.3.

You might need to adjust this if you're working from a restored backup copy of your 9.1 datadir, because its permissions may not be those of the postgres user. It does not matter what user owns it, but you might need to tweak pg_hba.conf if you're using peer auth and connecting as a different user.

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