apache/hadoop · error · FileAlreadyExistsException

Path {strB} already exists as dir; cannot create link here

Error message

Path {strB} already exists as dir; cannot create link here

What it means

When the last component of a new link's source path already exists in the inode tree (typically an internal directory created earlier by a deeper mount), InodeTree throws FileAlreadyExistsException('Path <path> already exists as dir; cannot create link here'). A directory and a link cannot occupy the same mount point.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/InodeTree.java:476

          throw new FileAlreadyExistsException("Path " + nextInode.fullPath +
              " already exists as link");
        }
      } else {
        assert(nextInode.isInternalDir());
        curInode = (INodeDir<T>) nextInode;
      }
    }

    // Now process the last component
    // Add the link in 2 cases: does not exist or a link exists
    String iPath = srcPaths[i];// last component
    if (curInode.resolveInternal(iPath) != null) {
      //  directory/link already exists
      StringBuilder strB = new StringBuilder(srcPaths[0]);
      for (int j = 1; j <= i; ++j) {
        strB.append('/').append(srcPaths[j]);
      }
      throw new FileAlreadyExistsException("Path " + strB +
          " already exists as dir; cannot create link here");
    }

    final INodeLink<T> newLink;
    final String fullPath = curInode.fullPath + (curInode == root ? "" : "/")
        + iPath;
    switch (linkType) {
    case SINGLE:
      newLink = new INodeLink<T>(fullPath, aUgi,
          initAndGetTargetFs(), target);
      break;
    case SINGLE_FALLBACK:
    case MERGE_SLASH:
      // Link fallback and link merge slash configuration
      // are handled specially at InodeTree.
      throw new IllegalArgumentException("Unexpected linkType: " + linkType);
    case MERGE:
    case NFLY:

View on GitHub (pinned to 2add963021)

Solutions

1. Delete the duplicate or conflicting entry so each source path is claimed exactly once
2. Order and deduplicate mount keys when generating configuration
3. Search every active config source for the offending fs.viewfs.mounttable keys

Example fix

<!-- before: /a/b mounted, then /a linked at the occupied dir -->
<property><name>fs.viewfs.mounttable.cluster.link./a/b</name>
  <value>hdfs://nnB/b</value></property>
<property><name>fs.viewfs.mounttable.cluster.link./a</name>
  <value>hdfs://nnA/a</value></property>

<!-- after: one owner for /a -->
<property><name>fs.viewfs.mounttable.cluster.link./a/b</name>
  <value>hdfs://nnB/b</value></property>

static boolean hasDuplicateMountSources(Collection<String> srcs) {
  return new HashSet<>(srcs).size() != srcs.size();
}

Catch FileAlreadyExistsException at ViewFileSystem init; 'already exists as dir; cannot create link here' means a link and a directory claim the same path — locate both fs.viewfs.mounttable entries across all config files and keep one.

When it happens

Trigger: Mount entries that first create internal directories (e.g. link./a/b) and then try to link at the same position (e.g. link./a); duplicate link, fallback or nfly entries for the same source path.

Common situations: Appending a root-level link after deeper mounts exist; configuration assembled from multiple files (core-site.xml plus an included file) that both claim the same path.

Related errors

• Path {nextInode.fullPath} already exists as link
• ViewFs: Non absolute mount name in config:{src}
• Unexpected mount table link entry '{key}'. Use linkMergeSlas
• ViewFs: Cannot initialize: Invalid entry in Mount table in c
• getServerDefaults on empty path is invalid

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/fee9499a0d749367. Report an issue: GitHub.