Suppose I had a "friend" with a PostgreSQL 9.6 instance (a large single node)... what's the best way to upgrade to PostgreSQL 14?
If you're on a single node, probably something like this. This is what my "friend" is doing later this week. He's migrating from 9.5 to 13:
sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main" > /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 install postgresql-13
sudo service postgresql stop
sudo mkdir -p /secure/pgsql13/data
sudo chown -R postgres:postgres /secure/pgsql13/data
sudo -u postgres /usr/lib/postgresql/13/bin/initdb -D /secure/pgsql13/data
sudo rm -rf /var/lib/postgresql/13/main
sudo ln -s /secure/pgsql13/data /var/lib/postgresql/13/main
sudo chown -hR postgres:postgres /var/lib/postgresql/13/main
sudo ln -s /etc/postgresql/9.5/main/postgresql.conf /var/lib/postgresql/9.5/main/postgresql.conf
sudo chown -hR postgres:postgres /etc/postgresql/9.5/main/postgresql.conf
cd /tmp
sudo -u postgres time /usr/lib/postgresql/13/bin/pg_upgrade --old-bindir /usr/lib/postgresql/9.5/bin --new-bindir /usr/lib/postgresql/13/bin --old-datadir /var/lib/postgresql/9.5/main --new-datadir /var/lib/postgresql/13/main --link --check
sudo -u postgres time /usr/lib/postgresql/13/bin/pg_upgrade --old-bindir /usr/lib/postgresql/9.5/bin --new-bindir /usr/lib/postgresql/13/bin --old-datadir /var/lib/postgresql/9.5/main --new-datadir /var/lib/postgresql/13/main --link
sudo service postgresql start 13
sudo -u postgres "/usr/lib/postgresql/13/bin/vacuumdb" --all -j 32 --analyze-only
sudo -u postgres ./delete_old_cluster.sh