🟠 High   ⏱ 5–30 min  Last verified: 20 May 2026
Affected versions: CentOS Stream 9

📖 ~1 min read

Table of contents
  1. Symptom & Impact
  2. Environment & Reproduction
  3. Root Cause Analysis
  4. Quick Triage
  5. Step-by-Step Diagnosis
  6. Solution – Primary Fix
  7. Solution – Alternative Approaches
  8. Verification & Acceptance Criteria
  9. Rollback Plan
  10. Prevention & Hardening
  11. Related Errors & Cross-Refs
  12. References & Further Reading

Symptom & Impact

psql refuses local connections with peer auth errors.

Environment & Reproduction

Wrong OS user mapped to the database role.

Root Cause Analysis

`pg_hba.conf` uses `peer` for local but the OS user mismatches.

Quick Triage

Run `psql -U postgres` after `sudo -iu postgres`.

Step-by-Step Diagnosis

Inspect `/var/lib/pgsql/data/pg_hba.conf` and `pg_ident.conf`.

Illustrative mockup for centos-stream-9 — terminal_or_shell
PostgreSQL peer authentication failure diagnostics in terminal — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Adjust the `peer` rule to `md5`/`scram-sha-256` for app users.

Still having issues? Our IT Solutions & Services team can diagnose and resolve this for you. Get in touch for a free consultation.

Illustrative mockup for centos-stream-9 — logs_or_journal
journal and log evidence for PostgreSQL peer authentication failure — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Reload with `systemctl reload postgresql`.

Verification & Acceptance Criteria

Application connects with the correct role and method.

Rollback Plan

Revert pg_hba.conf if access becomes too open.

Prevention & Hardening

Prefer `scram-sha-256` and least-privilege roles.

Pairs with SELinux and listen_addresses misconfig.

Related tutorial: View the step-by-step tutorial for centos-stream-9.

View all centos-stream-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

PostgreSQL authentication documentation.

Need Expert Help?

If you cannot resolve this yourself, our team offers hands-on Server Management, Managed IT Services, and flexible Support Plans. Contact us today — we respond within one business day.