在HDFS中，提供了fsck命令，用于检查HDFS上文件和目录的健康状态、获取文件的block信息和位置信息等。
fsck命令必须由HDFS超级用户来执行，普通用户无权限。

一、fsck常用命令

1.hdfs数据块状态监测

hadoop dfsadmin -report | grep -i blocks

2.查看文件中损坏的块（-list-corruptfileblocks）

hdfs fsck /path/ -list-corruptfileblocks

3.将损坏的文件移动至/lost+found目录（-move）

hdfs fsck /path/file -move

4.删除损坏的文件（-delete）

hdfs fsck /path/file -delete

5.检查并列出所有文件状态（-files）

hdfs fsck /path/ -files

6.检查并打印正在被打开执行写操作的文件（-openforwrite）

hdfs fsck /path/ -openforwrite

7.打印文件的Block报告（-blocks）

需要和-files一起使用。
hdfs fsck /path/file -files -blocks

[hadoop@dev ~]$  hdfs fsck /logs/site/2015-08-08/lxw1234.log -files -blocks
FSCK started by hadoop (auth:SIMPLE) from /172.16.212.17 for path /logs/site/2015-08-08/lxw1234.log at Thu Aug 13 09:45:59 CST 2015
/logs/site/2015-08-08/lxw1234.log 7408754725 bytes, 56 block(s):  OK
0. BP-1034052771-172.16.212.130-1405595752491:blk_1075892982_2152381 len=134217728 repl=2
1. BP-1034052771-172.16.212.130-1405595752491:blk_1075892983_2152382 len=134217728 repl=2
2. BP-1034052771-172.16.212.130-1405595752491:blk_1075892984_2152383 len=134217728 repl=2

其中，/logs/site/2015-08-08/lxw1234.log 7408754725 bytes, 56 block(s)：表示文件的总大小和block数；
0. BP-1034052771-172.16.212.130-1405595752491:blk_1075892982_2152381 len=134217728 repl=2
1. BP-1034052771-172.16.212.130-1405595752491:blk_1075892983_2152382 len=134217728 repl=2
2. BP-1034052771-172.16.212.130-1405595752491:blk_1075892984_2152383 len=134217728 repl=2
前面的0. 1. 2.代表该文件的block索引，56的文件块，就从0-55;
BP-1034052771-172.16.212.130-1405595752491:blk_1075892982_2152381表示block id；
len=134217728 表示该文件块大小；
repl=2 表示该文件块副本数；

8.打印文件块的位置信息（-locations）

需要和-files -blocks一起使用。
hdfs fsck /path/file -files -blocks -locations

[hadoop@dev ~]$  hdfs fsck /logs/site/2015-08-08/lxw1234.log -files -blocks -locations
FSCK started by hadoop (auth:SIMPLE) from /172.16.212.17 for path /logs/site/2015-08-08/lxw1234.log at Thu Aug 13 09:45:59 CST 2015
/logs/site/2015-08-08/lxw1234.log 7408754725 bytes, 56 block(s):  OK
0. BP-1034052771-172.16.212.130-1405595752491:blk_1075892982_2152381 len=134217728 repl=2 [172.16.212.139:50010, 172.16.212.135:50010]
1. BP-1034052771-172.16.212.130-1405595752491:blk_1075892983_2152382 len=134217728 repl=2 [172.16.212.140:50010, 172.16.212.133:50010]
2. BP-1034052771-172.16.212.130-1405595752491:blk_1075892984_2152383 len=134217728 repl=2 [172.16.212.136:50010, 172.16.212.141:50010]
3. BP-1034052771-172.16.212.130-1405595752491:blk_1075892985_2152384 len=134217728 repl=2 [172.16.212.133:50010, 172.16.212.135:50010]

和打印出的文件块信息相比，多了一个文件块的位置信息：[172.16.212.139:50010, 172.16.212.135:50010]

9.打印文件块位置所在的机架信息（-racks）

hdfs fsck /path/file -files -blocks -locations -racks

[hadoop@dev ~]$  hdfs fsck /logs/site/2015-08-08/lxw1234.log -files -blocks -locations -racks
FSCK started by hadoop (auth:SIMPLE) from /172.16.212.17 for path /logs/site/2015-08-08/lxw1234.log at Thu Aug 13 09:45:59 CST 2015
/logs/site/2015-08-08/lxw1234.log 7408754725 bytes, 56 block(s):  OK
0. BP-1034052771-172.16.212.130-1405595752491:blk_1075892982_2152381 len=134217728 repl=2 [/default-rack/172.16.212.139:50010, /default-rack/172.16.212.135:50010]
1. BP-1034052771-172.16.212.130-1405595752491:blk_1075892983_2152382 len=134217728 repl=2 [/default-rack/172.16.212.140:50010, /default-rack/172.16.212.133:50010]
2. BP-1034052771-172.16.212.130-1405595752491:blk_1075892984_2152383 len=134217728 repl=2 [/default-rack/172.16.212.136:50010, /default-rack/172.16.212.141:50010]
3. BP-1034052771-172.16.212.130-1405595752491:blk_1075892985_2152384 len=134217728 repl=2 [/default-rack/172.16.212.133:50010, /default-rack/172.16.212.135:50010]

和前面打印出的信息相比，多了机架信息：[/default-rack/172.16.212.139:50010, /default-rack/172.16.212.135:50010]

二、hdfs生产数据块损坏修复方法

1.查看丢失块