apache/hadoop · error · IOException

Mount table {mountTableName} has already been configured wit

Error message

Mount table {mountTableName} has already been configured with a merge slash link. Multiple merge slash links for the same mount table is not allowed.

What it means

Error "Mount table {mountTableName} has already been configured with a merge slash link. Multiple merge slash links for the same mount table is not allowed." thrown in apache/hadoop.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/InodeTree.java:710

      }

      final String target = si.getValue();
      if (linkType != LinkType.MERGE_SLASH) {
        if (isMergeSlashConfigured) {
          throw new IOException("Mount table " + mountTableName
              + " has already been configured with a merge slash link. "
              + "A regular link should not be added.");
        }
        linkEntries.add(
            new LinkEntry(src, target, linkType, settings, ugi, config));
      } else {
        if (!linkEntries.isEmpty()) {
          throw new IOException("Mount table " + mountTableName
              + " has already been configured with regular links. "
              + "A merge slash link should not be configured.");
        }
        if (isMergeSlashConfigured) {
          throw new IOException("Mount table " + mountTableName
              + " has already been configured with a merge slash link. "
              + "Multiple merge slash links for the same mount table is "
              + "not allowed.");
        }
        isMergeSlashConfigured = true;
        mergeSlashTarget = target;
      }
    } // End of for loop.

    if (isMergeSlashConfigured) {
      Preconditions.checkNotNull(mergeSlashTarget);
      root = new INodeLink<T>(mountTableName, ugi,
          initAndGetTargetFs(), mergeSlashTarget);
      mountPoints.add(new MountPoint<T>("/", (INodeLink<T>) root));
      rootFallbackLink = null;
    } else {
      root = new INodeDir<T>("/", UserGroupInformation.getCurrentUser());
      getRootDir().setInternalDirFs(getTargetFileSystem(getRootDir()));

View on GitHub (pinned to 2add963021)

Solutions

1. Configure only one linkMergeSlash entry per mount table.
2. Remove the duplicate merge slash link entries from the configuration.

When it happens

Trigger: Thrown during ViewFs mount table initialization when more than one merge-slash link is configured for the same mount table.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/742aadc80f734906. Report an issue: GitHub.