apache/hadoop · error · IOException

No such group:" + group

Error message

No such group:" + group

What it means

ShellBasedIdMapping.getGid mirrors getUid for groups: it checks the cached gidNameMap, on a miss runs updateMapIncr for that group, and throws IOException('No such group:<group>') when the group still cannot be found in the OS name service or static mapping.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/ShellBasedIdMapping.java:654

    if (id == null) {
      updateMapIncr(user, false);
      id = uidNameMap.inverse().get(user);
      if (id == null) {
        throw new IOException("User just deleted?:" + user);
      }
    }
    return id.intValue();
  }

  synchronized public int getGid(String group) throws IOException {
    checkAndUpdateMaps();

    Integer id = gidNameMap.inverse().get(group);
    if (id == null) {
      updateMapIncr(group, true);
      id = gidNameMap.inverse().get(group);
      if (id == null) {
        throw new IOException("No such group:" + group);
      }
    }
    return id.intValue();
  }

  synchronized public String getUserName(int uid, String unknown) {
    checkAndUpdateMaps();
    String uname = uidNameMap.get(uid);
    if (uname == null) {
      try {
        updateMapIncr(uid, false);
      } catch (Exception e) {        
      }
      uname = uidNameMap.get(uid);
      if (uname == null) {     
        LOG.warn("Can't find user name for uid " + uid
            + ". Use default user name " + unknown);
        uname = unknown;

View on GitHub (pinned to 2add963021)

Solutions

1. Verify with 'getent group <group>' and 'id <user>' on the mapping host
2. Add the group to the OS, or map it via the static ID mapping file (default /etc/nfs.static.map)
3. Repair LDAP/NSS lookups if the group exists upstream
4. Ensure gateway hosts can enumerate the same directory used by clients

Example fix

# before: group 'hadoop-eng' not present on gateway host
sudo groupadd -g 2500 hadoop-eng

# or /etc/nfs.static.map entry
hadoop-eng 2500

static boolean groupResolvable(String group) throws IOException {
  Process p = new ProcessBuilder("getent", "group", group).start();
  try { return p.waitFor() == 0; }
  finally { p.destroy(); }
}
// call before idMapping.getGid(group)

When it happens

Trigger: Calling getGid with a group name that has no entry in /etc/group (or the NSS backend) and no static mapping entry; typical when chown/chgrp operations through the NFS gateway reference groups unknown to the gateway host.

Common situations: Gateway hosts not joined to the same directory as clients; groups renamed or deleted in LDAP while files still reference them; missing static mapping coverage for synthetic groups.

Related errors

• User just deleted?:" + user
• Can't parse " + mapName + " list entry:" + line
• Number of group names and ids do not match. group name =" +
• The user name '" + userName + "' is not found. " + errMessag
• failed to get group id list for user '" + userName + "'

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/157bc49a04842794. Report an issue: GitHub.