document upgrade process

README.md

@@ -1,3 +1,64 @@
+# Operational notes
+
+## Postgres upgrade
+
+1. Stop services that use postgres
+```bash
+systemctl stop matrix-synapse grafana
+```
+2. Login as postgres user
+```bash
+sudo -su postgres
+old=16
+cd /var/lib/postgresql/
+pg_old=$(nix-build --no-out-link -A postgresql_${old:?} '<nixpkgs>')
+pg_new=$(nix-build --no-out-link -A postgresql_$((old+1)) '<nixpkgs>')
+```
+3. Initialize new data directory
+```bash
+$pg_new/bin/initdb --encoding=UTF8 --no-locale $((old+1))
+```
+4. Run check
+```bash
+$pg_new/bin/pg_upgrade \
+	--old-bindir=$pg_old/bin \
+	--new-bindir=$pg_new/bin \
+	--old-datadir=/var/lib/postgresql/${old:?} \
+	--new-datadir=/var/lib/postgresql/$((old+1)) \
+	-j16 \
+	--clone \
+	--check
+```
+5. Stop the old Postgres
+```bash
+systemctl stop postgresql
+```
+6. Run the migration
+```bash
+$pg_new/bin/pg_upgrade \
+	--old-bindir=$pg_old/bin \
+	--new-bindir=$pg_new/bin \
+	--old-datadir=/var/lib/postgresql/${old:?} \
+	--new-datadir=/var/lib/postgresql/$((old+1)) \
+	-j16 \
+	--clone
+```
+7. Start the new Postgres
+```bash
+services.postgres.packages = pkgs.postgresql_17;
+nixos-rebuild switch
+```
+
+Cleanup (after a few days):
+
+```bash
+sudo -su postgres
+vacuumdb --all --analyze-in-stages
+cd /var/lib/postgresql/
+./delete_old_cluster.sh
+rm -v delete_old_cluster.sh
+```
+
 # Tarball
 
 ```bash