{"record":{"id":"98bf6c42808b51e0","repo":"apache/hadoop","slug":"mount-table-mounttablename-has-already-been-conf-98bf6c","errorCode":null,"errorMessage":"Mount table {mountTableName} has already been configured with a link fallback. Multiple fallback links for the same mount table is not allowed.","messagePattern":"Mount table (.+?) has already been configured with a link fallback\\. Multiple fallback links for the same mount table is not allowed\\.","errorType":"validation","errorClass":"IOException","httpStatus":null,"severity":"error","filePath":"hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/InodeTree.java","lineNumber":736,"sourceCode":"    } // End of for loop.\n\n    if (isMergeSlashConfigured) {\n      Preconditions.checkNotNull(mergeSlashTarget);\n      root = new INodeLink<T>(mountTableName, ugi,\n          initAndGetTargetFs(), mergeSlashTarget);\n      mountPoints.add(new MountPoint<T>(\"/\", (INodeLink<T>) root));\n      rootFallbackLink = null;\n    } else {\n      root = new INodeDir<T>(\"/\", UserGroupInformation.getCurrentUser());\n      getRootDir().setInternalDirFs(getTargetFileSystem(getRootDir()));\n      getRootDir().setRoot(true);\n      INodeLink<T> fallbackLink = null;\n\n      for (LinkEntry le : getLinkEntries(linkEntries)) {\n        switch (le.getLinkType()) {\n        case SINGLE_FALLBACK:\n          if (fallbackLink != null) {\n            throw new IOException(\"Mount table \" + mountTableName\n                + \" has already been configured with a link fallback. \"\n                + \"Multiple fallback links for the same mount table is \"\n                + \"not allowed.\");\n          }\n          fallbackLink = new INodeLink<T>(mountTableName, ugi,\n              initAndGetTargetFs(), le.getTarget());\n          continue;\n        case REGEX:\n          addRegexMountEntry(le);\n          continue;\n        default:\n          createLink(le.getSrc(), le.getTarget(), le.getLinkType(),\n              le.getSettings(), le.getUgi(), le.getConfig());\n        }\n      }\n      rootFallbackLink = fallbackLink;\n      getRootDir().addFallbackLink(rootFallbackLink);\n    }","sourceCodeStart":718,"sourceCodeEnd":754,"githubUrl":"https://github.com/apache/hadoop/blob/2add9630210752f88ceb1bb74eb65e37bf41da8e/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/InodeTree.java#L718-L754","documentation":"Error \"Mount table {mountTableName} has already been configured with a link fallback. Multiple fallback links for the same mount table is not allowed.\" thrown in apache/hadoop.","triggerScenarios":"Thrown during ViewFs mount table initialization when more than one linkFallback entry is configured for the same mount table.","commonSituations":"See trigger scenarios.","solutions":["Configure only one linkFallback entry per mount table.","Remove the duplicate fallback link entries from the configuration."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"2add9630210752f88ceb1bb74eb65e37bf41da8e","analyzedAt":"2026-08-22T19:55:07.957Z","schemaVersion":2},"datasetVersion":"2026-08-23T01:17:44.959Z"}