Solution for hadoop Safe mode is ON

With a hadoop cluster environment, there are always errors in reading and writing files recently. Check the log of the name node ( Safe mode is ON)

1. Safe mode is ON. The ratio of reported blocks 0.2000 has not reached the threshold 0.9990. Safe mode will be turned off automatically.

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1. org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot delete /home/hadoop/tmp/mapred/system. Name node is in safe mode.

There are three google solutions

1) Execute the command: bin/hadoop dfsadmin -safemode leave

The description of the dfsadmin -safemode value parameter value is as follows:

enter - enter safe mode

leave - Force the NameNode to leave safe mode

get - returns information about whether safe mode is enabled

wait - Wait for safe mode to end.

2) Reformatting the filesystem = . =

3）bin/hadoop fsck /

The first method needs to be executed every time, which is very tangled~

The second method, you know what format means. . . .

The third method, if there is a lot of data, it will be very slow to execute, there is no way, just wait.

1. hadoop@mhadoop:~/hadoop-1.0.0$ bin/hadoop fsck /
2. FSCK started by hadoop from /192.168.1.110 for path / at Wed Mar 07 17:57:43 CST 2012
3. .
4. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0001/job.jar: CORRUPT block blk_-8710406465335110666
6. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0001/job.jar: MISSING 1 blocks of total size 142465 B..
7. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0002/job.jar: CORRUPT block blk_8343735010139595189
9. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0002/job.jar: MISSING 1 blocks of total size 142465 B..
10. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0004/job.jar: CORRUPT block blk_4796918520991551976
12. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0004/job.jar: MISSING 1 blocks of total size 142465 B..
13. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0005/job.jar: CORRUPT block blk_8732649167016211914
15. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0005/job.jar: MISSING 1 blocks of total size 142465 B..
16. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0006/job.jar: CORRUPT block blk_2190395249671123528
18. /tmp/hadoop/tmp/mapred/staging/hadoop/.staging/job_201202290728_0006/job.jar: MISSING 1 blocks of total size 142465 B..
19. /tmp/hadoop/tmp/mapred/system/jobtracker.info: Under replicated blk_3010497672022840180_1511. Target Replicas is 2 but found 1 replica(s).
20. .
21. /user/hadoop/input/README.txt: Under replicated blk_1278803782511847062_1510. Target Replicas is 2 but found 1 replica(s).
22. ..
23. /user/hadoop/output/_logs/history/job_201202290728_0007_1330473591943_hadoop_word+count: CORRUPT block blk_-165491155081655193
25. /user/hadoop/output/_logs/history/job_201202290728_0007_1330473591943_hadoop_word+count: MISSING 1 blocks of total size 13581 B..
26. /user/hadoop/output/_logs/history/job_201202290728_0007_conf.xml: CORRUPT block blk_359906738089887519
28. /user/hadoop/output/_logs/history/job_201202290728_0007_conf.xml: MISSING 1 blocks of total size 20344 B..
29. /user/hadoop/output/part-r-00000: CORRUPT block blk_-3883649133311907523
31. /user/hadoop/output/part-r-00000: MISSING 1 blocks of total size 158081 B.Status: CORRUPT
32. Total size: 905701 B
33. Total dirs: 20
34. Total files: 11
35. Total blocks (validated): 10 (avg. block size 90570 B)
36. ********************************
37. CORRUPT FILES: 8
38. MISSING BLOCKS: 8
39. MISSING SIZE: 904331 B
40. CORRUPT BLOCKS: 8
41. ********************************
42. Minimally replicated blocks: 2 (20.0 %)
43. Over-replicated blocks: 0 (0.0 %)
44. Under-replicated blocks: 2 (20.0 %)
45. Mis-replicated blocks: 0 (0.0 %)
46. Default replication factor: 2
47. Average block replication: 0.2
48. Corrupt blocks: 8
49. Missing replicas: 2 (100.0 %)
50. Number of data-nodes: 1
51. Number of racks: 1
52. FSCK ended at Wed Mar 07 17:57:43 CST 2012 in 11 milliseconds
55. The filesystem under path '/' is CORRUPT