Скачать или смотреть Resolving PostgreSQL Data Directory Permission Problems with repmgr

Discover the solution for PostgreSQL data directory ownership issues when setting up replication with repmgr. Follow this guide to ensure smooth service startup!
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Troubleshooting PostgreSQL Data Directory Permission Issues with repmgr

Setting up a PostgreSQL replica server using repmgr can be a smooth process, but sometimes, users encounter permission problems that can stall their progress. One common issue involves the data directory ownership and permission settings, which prevent the PostgreSQL service from starting. In this guide, we’ll dive into a specific scenario involving permission troubles in the data directory and how to efficiently resolve them.

The Problem

A user attempting to launch the PostgreSQL service on a standby server encountered the following error message when using journalctl:

[[See Video to Reveal this Text or Code Snippet]]

This error indicates that the PostgreSQL service is trying to access a data directory that is not owned by the correct user. In this case, the directory was owned by a normal user instead of the postgres user, which is required for PostgreSQL to function correctly.

Here's a quick breakdown of the relevant configuration from the user's repmgr.conf file:

[[See Video to Reveal this Text or Code Snippet]]

Understanding Permissions and Ownership

Key Concepts

User Ownership: The PostgreSQL service must run as the postgres user in order to access the data directory.

Directory Permissions: The data directory must have permissions set to 700, meaning only the owner can read, write, or execute within that directory.

The Dilemma

In this case, when the user set the ownership of the data directory to postgres:postgres, the repmgr service could not function since it was not able to access the directory. This resulted in a predicament where the PostgreSQL service wouldn't start, and repmgr couldn't operate effectively.

The Solution

The resolution involved a fundamental aspect of PostgreSQL database setup. The user had initially created a PostgreSQL database using initdb, which was unnecessary. Here's how they effectively resolved the issue:

Delete the Existing Database: The user removed the PostgreSQL instance they previously created.

Run repmgr as the Postgres User: After cleaning up, they executed repmgr as the postgres user. This resolved the permissions issue since repmgr was now running in the correct context, aligning with PostgreSQL's ownership requirements.

Summary of Steps

To resolve similar permission issues with PostgreSQL and repmgr:

Ensure the data directory is owned by the postgres user.

Set the correct permissions:

Run chmod 700 /mnt/data/postgres/data to allow full access only to the owner.

Avoid unnecessary initializations with initdb that may create conflict.

Always run repmgr commands as the postgres user to prevent ownership problems.

Conclusion

By understanding and correctly configuring the data directory permissions along with the appropriate user ownership, you can successfully manage your PostgreSQL replication setup without hindrance. If you ever run into issues similar to those discussed in this post, remember to check your directory ownership and user context first. Happy database replicating!