apache/hadoop · error · IOException

ViewFs: Cannot initialize: Invalid entry in Mount table in c

Error message

ViewFs: Cannot initialize: Invalid entry in Mount table in config: {src}

What it means

While parsing fs.viewfs.mounttable.<name>.* keys, InodeTree maps each key suffix to a known kind: link., linkNfly., link fallback, linkMerge., linkMergeSlash., linkRegex, homedir. A suffix matching none of them reaches the final else and throws IOException('ViewFs: Cannot initialize: Invalid entry in Mount table in config: <src>') with the raw suffix for easy identification.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/InodeTree.java:690

        src = src.substring(Constants.CONFIG_VIEWFS_LINK_NFLY.length() + 1);
        // settings.src
        settings = src.substring(0, src.indexOf('.'));
        // settings

        // settings.src
        src = src.substring(settings.length() + 1);
        // src

        linkType = LinkType.NFLY;
      } else if (src.startsWith(Constants.CONFIG_VIEWFS_LINK_REGEX)) {
        linkEntries.add(
            buildLinkRegexEntry(config, ugi, src, si.getValue()));
        continue;
      } else if (src.startsWith(Constants.CONFIG_VIEWFS_HOMEDIR)) {
        // ignore - we set home dir from config
        continue;
      } else {
        throw new IOException("ViewFs: Cannot initialize: Invalid entry in " +
            "Mount table in config: " + src);
      }

      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.");
        }

View on GitHub (pinned to 2add963021)

Solutions

1. Correct the prefix to a supported kind (link., linkMerge., linkMergeSlash., linkNfly., linkRegex, fallback, homedir)
2. Remove unrelated properties from under fs.viewfs.mounttable.<name>.
3. When the error names a suffix, grep every config source for that suffix to find the offending key

Example fix

<!-- before -->
<property><name>fs.viewfs.mounttable.cluster.lnk./data</name>
  <value>hdfs://nnA/data</value></property>

<!-- after -->
<property><name>fs.viewfs.mounttable.cluster.link./data</name>
  <value>hdfs://nnA/data</value></property>

static final List<String> VALID_PREFIXES = Arrays.asList(
    "link.", "linkMerge.", "linkMergeSlash", "linkNfly.", "linkRegex", "homedir");
static boolean isValidMountKeySuffix(String suffix) {
  return VALID_PREFIXES.stream().anyMatch(suffix::startsWith);
}

Catch IOException at ViewFileSystem init; the message includes the invalid suffix — grep all configuration sources for that suffix and correct or remove the key.

When it happens

Trigger: Typos in key prefixes: fs.viewfs.mounttable.X.lnk./data, ...X.links./data, unknown kinds like ...X.mount./data, or stray properties placed under the mounttable prefix.

Common situations: Hand-edited core-site.xml; config generation that drops or doubles the dot; unrelated properties inherited under fs.viewfs.mounttable.<name>.

Related errors

• ViewFs: Non absolute mount name in config:{src}
• Path {nextInode.fullPath} already exists as link
• Path {strB} already exists as dir; cannot create link here
• Unexpected mount table link entry '{key}'. Use linkMergeSlas
• getServerDefaults on empty path is invalid

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/6683f32c49740633. Report an issue: GitHub.