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How to Change the PostgreSQL Data Directory on Ubuntu

How to Change the PostgreSQL Data Directory on Ubuntu
Hostman Team
Technical writer
PostgreSQL
18.12.2024
Reading time: 4 min

Databases tend to grow beyond their original filesystem over time. If they share the same partition as the operating system, it could potentially lead to I/O conflicts.

Devices like network block storage RAID provide redundancy and enhance scalability. Regardless of your goals—whether increasing space or optimizing performance—this guide will assist you in moving the PostgreSQL data directory.

Prerequisites

To follow this guide, you will need:

  • An Ubuntu 22.04 VPS server with a non-privileged user account and sudo privileges.

  • PostgreSQL installed on your server.

In this guide, we will move the data to a block storage device mounted at /mnt/volume_01. The method described here is universal and will help relocate the data directory to another location in any basic storage.

Step 1. Move the PostgreSQL Data Directory

First, check the current location of the data directory by starting an interactive PostgreSQL session. Here, psql is the command to enter the interactive monitor, and -u postgres instructs sudo to run psql as the system user postgres:

sudo -u postgres psql

In the PostgreSQL command line, enter this command to show the current directory:

SHOW data_directory;

By default, the directory is /var/lib/postgresql/xx/main, where xx is your PostgreSQL version.

Exit the PostgreSQL prompt by typing \q and pressing ENTER.

Before making any changes to the directory, stop PostgreSQL to avoid compromising data integrity:

sudo systemctl stop postgresql

You won’t be able to check the service status directly through systemctl after stopping it. To ensure the service has been stopped, run the following command:

sudo systemctl status postgresql

The last line of the output will confirm that PostgreSQL has indeed stopped.

To copy the directory to the new location, use the rsync command. You can add flags: -a preserves the permissions and other attributes of the directory, while -v ensures detailed output so you can track progress. To replicate the original directory structure in the new location, run rsync from the postgresql directory. Creating this postgresql directory at the mount point and preserving ownership by the PostgreSQL user will prevent permission issues during future updates.

Note: If tab completion is enabled, make sure the directory doesn't have a trailing slash. Otherwise, rsync will only copy the directory's contents to the mount point, not the directory itself.

Strictly speaking, the versioned directory (e.g., 16) is unnecessary since the location is explicitly defined in the postgresql.conf file. However, it is recommended to follow the project's conventions, especially if you later need to run multiple versions of PostgreSQL:

sudo rsync -av /var/lib/postgresql /mnt/volume_01

Once the copy is complete, rename the original folder with a .bak extension, and don't delete it until the move is complete. This ensures that nothing gets mixed up due to directories with the same name:

sudo mv /var/lib/postgresql/16/main /var/lib/postgresql/10/main.bak

Now, we can configure PostgreSQL to access the data directory in the new location.

Step 2. Point to the New Location of the Directory

By default, the value for data_directory is set to /var/lib/postgresql/16/main in the file /etc/postgresql/16/main/postgresql.conf. You need to edit this file to point to the new directory:

sudo nano /etc/postgresql/16/main/postgresql.conf

Now, locate the line starting with data_directory and change the path to point to the new location. The updated directive will look something like this:

# /etc/postgresql/16/main/postgresql.conf
...
data_directory = '/mnt/volume_01/postgresql/10/main'
...

Save the file and close it by pressing CTRL+X, then Y, and finally ENTER. No further configuration is needed for PostgreSQL in the new directory. The only thing left to do at this point is restart the PostgreSQL service and verify that it correctly points to the new data directory.

Step 3. Restart PostgreSQL

After changing the data_directory directive in the postgresql.conf file, start the PostgreSQL server using systemctl:

sudo systemctl start postgresql

Check the server status:

sudo systemctl status postgresql

If the service started correctly, you will see a line like this at the end of the output.

Finally, to ensure that the new directory is being used, open the PostgreSQL command line:

sudo -u postgres psql

Check the value of the data directory again:

SHOW data_directory;

The output will confirm that PostgreSQL is using the new data directory location. After verifying that everything is working properly, ensure you have access to your database and can interact with its data without issues. Once you are confident that the existing data is intact, you can delete the backup directory:

sudo rm -Rf /var/lib/postgresql/16/main.bak

Thus, you have successfully moved the PostgreSQL data directory to a new location.

Conclusion

If you followed the instructions correctly, your database directory is now in a new location, and you're closer to being able to scale your storage. Congrats!

PostgreSQL
18.12.2024
Reading time: 4 min

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But it would be wiser to rename it to leave room for restoring data. Instead of /usr/local/pgsql, specify the path to your directory. Install the new version from source. There is a detailed guide in the documentation.  Form a new cluster: /usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data Transfer all changes to the pg_hba.conf and postgresql.conf files. Start the database server: /usr/local/pgsql/bin/postgres -D /usr/local/pgsql/data Restore data from backup: /usr/local/pgsql/bin/psql -d postgres -f output_file The disadvantage of this method is that the server will be turned off for a long time. To reduce downtime, you can install the new server in a different directory and then run the old and new servers on different ports. To transfer data, use the command: pg_dumpall -p 5432 | psql -d postgres -p 5433 Instead of 5432 and 5433, specify the port numbers on which you ran the servers. Upgrading via pg_upgrade To avoid unloading and uploading data, use the pg_upgrade program. It helps you update faster. The pg_upgrade program creates system tables anew, taking into account changes in the PostgreSQL latest versions. In this case, the old data files are retained. In addition, pg_upgrade verifies that the clusters are compatible. The pg_upgrade program helps you upgrade from PostgreSQL 8.4.X to the current DBMS release. Let's look at a general upgrade plan using pg_upgrade. Move the old cluster. This must be done if the directory was not linked to the old release. For example, it is located at /usr/local/pgsql. If you do not rename it, a conflict will occur during the update. Renaming is performed when the server is turned off with the command: mv /usr/local/pgsql /usr/local/pgsql.old Build a new version from source. Adjust configure so that the flags are compatible with the old cluster configuration. Before starting the upgrade, pg_upgrade will check the compatibility of the flags. Install new executable files. To place the server in a non-standard directory, use prefix: make prefix=/usr/local/pgsql.new install Use initdb to initialize a new cluster. Check that the flags are compatible with the flags of the old cluster. Install extension shared object files. If updates are available, pg_upgrade will automatically create a script for their subsequent installation. Transfer full text search files. Configure peer authentication in pg_hba.conf. This needs to be done because pg_upgrade will connect to the old and new hosts multiple times. Check that the old and new servers are stopped: pg_ctl -D /opt/PostgreSQL/9.6 stoppg_ctl -D /opt/PostgreSQL/14 stop Run pg_upgrade from the new server. First, call the program in check mode by adding the flag: pg_upgrade --check In response, you will receive a list of adjustments that need to be made manually after the upgrade. If you made changes to the pg_hba.conf file, restore it to its previou state. Sometimes, other configurations on the new cluster need to be changed to match the settings of the old cluster. Start the server. If you are satisfied with the result, delete the old cluster. For details and features of using pg_upgrade, see the documentation. Using Logical Replication Starting from the 10th version of PostgreSQL, we have a method for logical replication of data objects and changes in them. It is based on the use of replication identifiers; usually, they are primary keys. Logical replication uses the publish-subscribe model. The user creates a snapshot of the published database and copies it to the subscriber. In the PostgreSQL documentation, one of the typical scenarios for using logical replication is precisely the replication between different major versions of PostgreSQL. The backup server can be located on the same or different host. After synchronization is complete, various options are available. For example, you can make the new server the main one and turn off the old one. The main advantage of logical replication is minimal downtime. Server interruption, in some cases, is limited to a few seconds. Conclusion We looked at universal methods for upgrading PostgreSQL to a new major version and updating within one major version. Using this guide, you can select the method that works best for your particular case and update your current version of PostgreSQL. Hostman provides pre-configured and ready-to-use cloud databases, including cloud PostgreSQL.
04 May 2025 · 7 min to read

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