liugen@ubuntu:~$ hdfs fsck /
Connecting to namenode via http://localhost:9870/fsck?ugi=liugen&path=%2F
FSCK started by liugen (auth:SIMPLE) from /127.0.0.1 for path / at Wed Oct 24 20:39:11 PDT 2018
Status: HEALTHY //集群状态健康
Number of data-nodes: 1 //集群有多少数据节点
Number of racks: 1 //集群有多少机架
Total dirs: 7 //集群有多少个目录
Total symlinks: 0 //集群有多少链接
Replicated Blocks:
Total size: 54396813 B //集群总共文件大小
Total files: 3 //集群有多少个文件
Total blocks (validated): 2 (avg. block size 27198406 B) //多少个数据块 通过验证的有2块 平均块大小是27xxx
Minimally replicated blocks: 2 (100.0 %) //最少复制的块数
Over-replicated blocks: 0 (0.0 %) //超过预计复制数目的块有几个（比如说 多备份了1个副本）
Under-replicated blocks: 0 (0.0 %) // 少于预计复制数目的块有几个（比如说 3副本少备份了1个副本）
Mis-replicated blocks: 0 (0.0 %) //没备份的块有几个
Default replication factor: 1 //备份因子为1 每个数据块给1个备份
Average block replication: 1.0 //平均备份数目，1个备份
Missing blocks: 0
Corrupt blocks: 0
Missing replicas: 0 (0.0 %)
Erasure Coded Block Groups:
Total size: 0 B
Total files: 0
Total block groups (validated): 0
Minimally erasure-coded block groups: 0
Over-erasure-coded block groups: 0
Under-erasure-coded block groups: 0
Unsatisfactory placement block groups: 0
Average block group size: 0.0
Missing block groups: 0
Corrupt block groups: 0
Missing internal blocks: 0
FSCK ended at Wed Oct 24 20:39:11 PDT 2018 in 20 milliseconds
The filesystem under path '/' is HEALTHY