WARNING: *** Duplicate <driver-name> JAR files ***

Applies to

• Liquibase Secure (Pro)
• Liquibase Community (Open Source)

Conditions

• Liquibase v4.32.0-4.33.0

• JDBC driver JAR files included with Liquibase or added manually

• Custom --classpath usage or extra drivers placed in liquibase/lib

Issue Summary

When running Liquibase, you may see a warning about duplicate JAR files. This message can apply to any JDBC driver (for example: PostgreSQL, Oracle, MySQL), JAR file, or extension.

Error Message

WARNING: *** Duplicate <driver-name> JAR files ***

/liquibase/internal/lib/<driver>.jar
/liquibase/lib/<driver>.jar

(Exact paths may vary depending on your setup.)

Root Cause

Liquibase added this warning to help identify when multiple versions of the same driver or JARs are being loaded, which can cause conflicts.

By default, Liquibase ships with a single version of each supported JDBC driver and/or JAR in the liquibase/internal/lib folder. Liquibase automatically loads files from the liquibase/internal/lib, liquibase/internal/extensions, and liquibase/lib directories. 

This warning usually occurs for one of the following reasons:

1. Duplicate JAR files exist in the Liquibase install directory (i.e., liquibase/internal/lib, liquibase/internal/extensions, or liquibase/lib).

2. Classpath is explicitly set to point to a driver JAR that Liquibase already loads by default. For example:

   • liquibase --classpath=/liquibase/lib/<driver>.jar

3. Driver JARs exist in both liquibase/lib and liquibase/internal/lib, causing Liquibase to load the same driver from two different locations.

Resolution

1. Verify which JAR files are installed:

   • Review the contents of /liquibase/internal/lib, /liquibase/internal/extensions, and /liquibase/lib to confirm that there is only one JAR file, as indicated by your error message.

   • Run liquibase --version to confirm the expected JDBC driver version is being used.

2. Remove duplicates:

   • If you see multiple copies of the same JAR, keep only one copy (preferably the one that ships with Liquibase in liquibase/internal/lib).

3. Update your Liquibase command:

   • If you are explicitly setting --classpath to point to a driver that Liquibase already includes, remove that option to avoid loading it twice.

Once resolved, Liquibase should only load a single JDBC driver, and the warning will no longer appear.