$ hdfs dfsadmin –setSpaceQuota <N> <dirname>...<dirname>
清除设置
$ dfsadmin –clrSpaceQuota /user/alapati

Name quotas: Let you specify the maximum number of file and directory names in the tree rooted at a directory
设置最大文件数

$ hdfs dfsadmin –setQuota <max_number> <directory>

查询配额：
dfs –count –q

$ hdfs dfs –test –e /users/alapati/test

创建空文件

$ hdfs dfs -touchz /user/alapati/test3.txt

# hdfs dfs -df
Filesystem                     Size             Used        Available Use%
hdfs://hadoop01-ns 2068027170816000 1591361508626924  476665662189076  77%
#

查询使用情况
$ hdfs dfs –du URI

增加新的目录hdfs-site.xml

<property>
<name>df.data.dir</name>
value>/u01/hadoop/data,/u02/hadoop/data,/u03/hadoop/data</value>
</property>

<property>
<name>dfs.permissions.enabled</name>
<value>true</value>
</property>

HDFS uses a symbolic notation (r, w) to denote the read and write permissions, just as a Linux operating system does.

When a client accesses a directory, if the client is the same as the directory’s owner, Hadoop tests the owner’s permissions.

If the group matches the directory’s group, then Hadoop tests the user’s group permissions.

If neither the owner nor the group names match, Hadoop tests the “other” permission of the directory.

If none of the permissions checks succeed, the client’s request is denied.

修改权限
$ hdfs dfs –chmod –R 755 /user

HDFS本身没有用户和组的概念：
1.simple authentication 模式 依赖操作系统的用户和组
2.Kerberos模式

添加用户

$ group add analysts
$ useradd –g analysts alapati
$ passwd alapati

core-site.xml需要配置
<property>
  <name>hadoop.tmp.dir</name>
  <value>/tmp/hadoop-$(user.name)</value>
</property>

$ hdfs –dfs –chmod –R 777 //tmp/hadoop-alapati

$ hdfs dfs -mkdir /user/alapati

$ su hdfs
$ hdfs dfs –chown –R alapati:analysts
$ hdfs dfs –ls /user/
$ drwxr-xr-x   - alapati   analysts      0 2016-04-27 12:40 /user/alapati

$ hdfs dfsadmin -refreshUserToGroupMappings

$ hdfs dfsadmin -setSpaceQuota 30g /user/alapati

Configured Capacity: 2068027170816000 (1.84 PB) #A
Present Capacity: 2068027170816000 (1.84 PB)
DFS Remaining: 562576619120381 (511.66 TB) #A
DFS Used: 1505450551695619 (1.34 PB) #B
DFS Used%: 72.80% #B
Under replicated blocks: 1 #C
Blocks with corrupt replicas: 0
Missing blocks: 1
Missing blocks (with replication factor 1): 9 #C

Live datanodes (54): #D

Name: 10.192.0.78:50010 (hadoop02.localhost) #E
Hostname: hadoop02.localhost.com
Rack: /rack3 #E
Decommission Status : Normal #F
Configured Capacity: 46015524438016 (41.85 TB) #G
DFS Used: 33107988033048 (30.11 TB)
Non DFS Used: 0 (0 B)
DFS Remaining: 12907536404968 (11.74 TB)
DFS Used%: 71.95%
DFS Remaining%: 28.05% #G
Configured Cache Capacity: 4294967296 (4 GB) #H
Cache Used: 0 (0 B)
Cache Remaining: 4294967296 (4 GB)
Cache Used%: 0.00%
Cache Remaining%: 100.00% #H
Xceivers: 71
Last contact: Fri May 01 15:15:59 CDT 2015
#A Configured capacity for HDFS in this cluster
#B HDFS used storage statistics
#C Shows if there are any under-replicated, corrupt or missing blocks
#D Shows how many DataNodes in the cluster are alive and available
#E The hostname and rack name
#F Status of the DataNode (decommissioned or not)
#G Configured and used capacity for this DataNode
#H Cache usage statistics (if configured)

刷新节点信息
dfsadmin –refreshNodes
提供更详细的信息
dfsadmin –metasave