# Updating PostgreSQL cluster 12 and lower to version 18

> [HTML Version](upgrading-postgresql-cluster-10-to-15.html)

When updating PostgreSQL to a major version, the **pg\_upgrade** utility is used. This utility allows you to update the data stored in PostgreSQL data files to a newer version of PostgreSQL.

Updating a PostgreSQL cluster consists of six steps:

1. [Database backup](#database-backup).

2. [Installation of PostgreSQL 18](#install-postgresql15).

3. [Updating data in the database directory](#updating-data).

4. [Starting the Patroni cluster](#starting-patroni-cluster).

5. [Post-installation check](#check-after-installing).

6. [Cleaning up old data](#clear-old-data).

## Step 1. Database backup

Before carrying out any actions related to the update, create a backup of the PostgreSQL data and configuration. Read more about how to do this in [Backup and recover databases](database-backup-and-recovery.md).

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If there are third-party databases on the PostgreSQL server, backups of these databases should also be created.

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Backup of the PostgreSQL database without using the elma365-backupper utility

  
You can create an \[OBJECT\] database backup using \[OBJECT\] :

````
sudo -u postgres pg\_dump brix365 -Fc > path/to/brix365.bak 
````

## ````
Step 2. Installation of PostgreSQL 18

Install PostgreSQL 18 on all nodes of the cluster where version 12 or lower is installed:

````
sudo apt install postgresql-18

## ````
Step 3. Updating data in the database directory

1. In the PostrgeSQL cluster, identify the Leader node::

````
patronictl -c /etc/patroni/config.yml list

2. ````
Stop Patroni on all PostrgeSQL cluster nodes::

````
sudo systemctl stop patroni.service

3. ````
Stop PostgreSQL 12 or lower and PostgreSQL 18 on all cluster nodes:

````
sudo systemctl stop postgresql@12 postgresql@18

4. ````
Ensure that both PostgreSQL 12 or lower and PostgreSQL 18 clusters are stopped:

````
pg\_lsclusters

5. ````
On the Leader node, perform a compatibility check of database configurations:

````
sudo -iu postgres /usr/lib/postgresql/18/bin/pg\_upgrade \\  
\-o "-c config\_file=/etc/postgresql/12/main/postgresql.conf"\\  
\-O "-c config\_file=/etc/postgresql/18/main/postgresql.conf" \\  
\--old-datadir=/var/lib/postgresql/12/main/ \\  
\--new-datadir=/var/lib/postgresql/18/main/ \\  
\--old-bindir=/usr/lib/postgresql/12/bin \\  
\--new-bindir=/usr/lib/postgresql/18/bin --check

````
Where:

- \[OBJECT\] and \[OBJECT\] are the paths to the binary files of PostgreSQL versions 12 and 18.

- \[OBJECT\] and \[OBJECT\] are the paths to the data directories.

6. On the Leader node, transfer data from PostgreSQL 12 or lower to PostgreSQL 18:

````
sudo -iu postgres /usr/lib/postgresql/18/bin/pg\_upgrade \\  
\-o "-c config\_file=/etc/postgresql/12/main/postgresql.conf" \\  
\-O "-c config\_file=/etc/postgresql/18/main/postgresql.conf" \\  
\--old-datadir=/var/lib/postgresql/12/main/ \\  
\--new-datadir=/var/lib/postgresql/18/main/ \\  
\--old-bindir=/usr/lib/postgresql/12/bin \\  
\--new-bindir=/usr/lib/postgresql/18/bin

````
Where:

- \[OBJECT\] and \[OBJECT\] are the paths to the binary files of PostgreSQL versions 12 and 18.

- \[OBJECT\] and \[OBJECT\] are the paths to the data directories.

## Step 4. Starting the Patroni cluster

1. Open the Patroni configuration file on the path to PostgreSQL 18:

````
sudo nano /etc/patroni/config.yml

2. ````
Replace parameters  \[OBJECT\], \[OBJECT\] and \[OBJECT\] on each PostgreSQL cluster node, for example:

````
...  
data\_dir: /var/lib/postgresql/18/main  
bin\_dir: /usr/lib/postgresql/18/bin  
config\_dir: /etc/postgresql/18/main  
...

3. ````
Get the name of the PostgreSQL 12 or lower cluster:

````
sudo cat /etc/patroni/config.yml | grep "scope" | awk '\{ print \$2 \}'

4. ````
On the Leader node in Patroni, remove the PostgreSQL 12 or lower cluster:

````
patronictl -c /etc/patroni/config.yml remove postgres-cluster

````
Where \[OBJECT\] is the name of the PostgreSQL 12 or lower cluster obtained in the previous step.

5. Start Patroni on the Leader node:

````
sudo systemctl start patroni.service

6. ````
On Replica nodes, delete the PostgreSQL 18 data directory:

````
sudo rm -rf /var/lib/postgresql/18/main

7. ````
On Replica nodes, start Patroni:

````
sudo systemctl start patroni.service

## ````
Step 5. Post-installation check

1. Check the status of the cluster:

````
patronictl -c /etc/patroni/config.yml list

2. ````
Ensure that PostgreSQL 18 is running correctly and the data is accessible. 

3. For database optimization, execute the command on the Leader node:

````
sudo -u postgres /usr/lib/postgresql/18/bin/vacuumdb --all --analyze-in-stages

## ````
Step 6. Cleaning up old data

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Before starting the cleaning process, ensure you have a backup of the data and configuration.

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If necessary, after successful updating and checking PostgreSQL 18, you can clean up old data:

````
sudo -u postgres ./delete\_old\_cluster.sh
````