9.1. Service Users and Groups

The individual services in Hadoop are each run under the ownership of a corresponding Unix account. These accounts are known as service users. These service users belong to a special Unix group. In addition there is a special service user for running smoke tests on components during installation and on-demand using the Management Header in the Services View of the Ambari Web GUI. Any of these users and groups can be customized using the Misc tab of the Customize Services step.

If you choose to customize names, Ambari checks to see if these custom accounts already exist. If they do not exist, Ambari creates them. The default accounts are always created during installation whether or not custom accounts are specified. These default accounts are not used and can be removed post-install.

[Note] Note

All new service user accounts, and any existing user accounts used as service users, must have a UID >= 1000.

 

Table 3.1. Service Users

Service Component Default User Account
HDFS

NameNode

SecondaryNameNode

DataNode

hdfs
MapReduce

JobTracker

HistoryServer

TaskTracker

mapred
Hive

Hive Metastore

HiveServer2

hive
HCat HCatalog Server hcat
WebHCat WebHCat Server hcat
Oozie Oozie Server oozie
HBase

MasterServer

RegionServer

hbase
ZooKeeper ZooKeeper zookeeper
Ganglia

Ganglia Server

Ganglia Collectors

nobody
Nagios Nagios Server nagios[a]
Smoke Test[b] All ambari-qa

[a] If you plan to use an existing user account named "nagios", that "nagios" account must be in a group named "nagios". If you customize this account, that account will be created and put in a group "nagios".

[b] The Smoke Test user performs smoke tests against cluster services as part of the install process. It also can perform these on-demand from the Ambari Web GUI.


 

Table 3.2. Service Group

Service Components Default Group Account
All All hadoop



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