{"record":{"id":"b07b44f2f8c31aff","repo":"apache/hadoop","slug":"eio-b07b44","errorCode":"EIO","errorMessage":"fuseConnectAsThreadUid: failed to open a libhdfs connection!  error %d.\n","messagePattern":"fuseConnectAsThreadUid: failed to open a libhdfs connection!  error (.+?)\\.\n","errorType":"console","errorClass":null,"httpStatus":null,"severity":"error","filePath":"hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/fuse-dfs/fuse_impls_rename.c","lineNumber":48,"sourceCode":"\n  TRACE1(\"rename\", from) \n\n  // check params and the context var\n  assert(from);\n  assert(to);\n  assert(dfs);\n\n  assert('/' == *from);\n  assert('/' == *to);\n\n  if (is_protected(from) || is_protected(to)) {\n    ERROR(\"Could not rename %s to %s\", from, to);\n    return -EACCES;\n  }\n\n  ret = fuseConnectAsThreadUid(&conn);\n  if (ret) {\n    fprintf(stderr, \"fuseConnectAsThreadUid: failed to open a libhdfs \"\n            \"connection!  error %d.\\n\", ret);\n    ret = -EIO;\n    goto cleanup;\n  }\n  fs = hdfsConnGetFs(conn);\n  if (hdfsRename(fs, from, to)) {\n    ERROR(\"Rename %s to %s failed\", from, to);\n    ret = (errno > 0) ? -errno : -EIO;\n    goto cleanup;\n  }\n  ret = 0;\n\ncleanup:\n  if (conn) {\n    hdfsConnRelease(conn);\n  }\n  return ret;\n}","sourceCodeStart":30,"sourceCodeEnd":66,"githubUrl":"https://github.com/apache/hadoop/blob/2add9630210752f88ceb1bb74eb65e37bf41da8e/hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/fuse-dfs/fuse_impls_rename.c#L30-L66","documentation":"Emitted by the fuse-dfs rename handler when fuseConnectAsThreadUid() cannot obtain a libhdfs connection for the calling UID; the rename fails with EIO, so mv across/inside the mount reports 'Input/output error'. This error fires only after the is_protected() check (protected paths return EACCES instead), so it is purely a backend-connection failure, not a path or permission problem.","triggerScenarios":"mv on the fuse-dfs mount when getUsername(uid) fails (no passwd entry), the Kerberos ticket cache for the uid is missing/stale (fuseNewConnect -> EACCES), or hdfsBuilderConnect fails (JVM/CLASSPATH broken, wrong namenode URI or port in fuse_dfs.conf, NameNode down).","commonSituations":"Kerberized cluster where kinit was not run or the ticket expired after the mount was started; fuse_dfs started from an environment without Hadoop jars on CLASSPATH; fuse_dfs.conf with a stale namenode address after a cluster migration.","solutions":["Check fuse-dfs stderr for the preceding fuseNewConnect/fuseConnect message - it carries the actual error code or kinit hint.","If Kerberos: kinit as the accessing user and verify the ticket cache for that uid exists.","Validate connectivity with the same CLASSPATH: hdfs dfs -ls hdfs://<nn>:<port>/ must work before the mount can.","Confirm the uid has a local passwd entry so getUsername() succeeds.","Restart fuse_dfs with corrected CLASSPATH/LIBHDFS_OPTS/fuse_dfs.conf and remount."],"exampleFix":null,"handlingStrategy":"validation","validationCode":"# before bulk renames through the mount\nklist -s || kinit \"$USER\"@EXAMPLE.COM\nCLASSPATH=\"$(hdfs classpath --glob)\" hdfs dfs -ls \"${HDFS_URI:-hdfs://nn:8020/}\" || exit 1","typeGuard":null,"tryCatchPattern":"if (rename(mount_a, mount_b) < 0 && errno == EIO) {\n    /* fuse-dfs could not connect to HDFS as your uid; check fuse-dfs stderr */\n    fail_job_and_alert();\n}","preventionTips":["Run kinit (or a keytab refresh via k5start/reaper) on hosts mounting fuse-dfs.","Keep the fuse-dfs stderr log tailed by monitoring; EIO on the mount is only a symptom.","Test one rename after mount and after any credential renewal before launching bulk jobs.","Keep fuse_dfs.conf, CLASSPATH and NameNode address in sync with cluster changes."],"tags":["c","fuse-dfs","libhdfs","kerberos","connection","eio","rename"],"backgroundTag":"hdfs-connection-failed","analyzedSha":"2add9630210752f88ceb1bb74eb65e37bf41da8e","analyzedAt":"2026-08-22T19:55:07.957Z","schemaVersion":2},"datasetVersion":"2026-08-22T20:17:22.307Z"}