When permission control is enabled for HDFS, users need valid permissions to access HDFS for normal operations, such as reading data and creating a folder.
Configurations related to HDFS permission are as follows:
Enable permission check. Even if the value is false, chmod/chgrp/chown/setfacl performs permission check.
The permission of the local folder used by datanode, which is 755 by default.
Permissions mask. The default permission settings when creating a file/folder.
File creation: 0666 & ^umask
Folder creation: 0777 & ^umask
Default umask value is 022, i.e. the permission of file creation is 644 (666&^022 = 644), and permission of folder creation is 755 (777&^022 = 755).
The default setting of
Kerberos security clusterin the EMR is 027, the corresponding permission of file creation is 640, and permission of folder creation is 750.
Enable ACL control. This gives you permission control on owner/group, and you can also set it for other users.
Commands for setting ACL:
hadoop fs -getfacl [-R] <path>
hadoop fs -setfacl [-R] [-b |-k -m |-x <acl_spec> <path>] |[--set <acl_spec> <path>]
#The user test creates a folder
hadoop fs -mkdir /tmp/test
#View the permission of the created folder
hadoop fs -ls /tmp
drwxr-x--- - test hadoop 0 2017-11-26 21:18 /tmp/test
#Set ACL and grant rwx permissions to user foo
hadoop fs -setfacl -m user:foo:rwx /tmp/test
#View the permission of the file (+ means that ACL is set)
hadoop fs -ls /tmp/
drwxrwx---+ - test hadoop 0 2017-11-26 21:18 /tmp/test
hadoop fs -getfacl /tmp/test
# file: /tmp/test
# owner: test
# group: hadoop
Super user group. Users in the group have super user permissions.
Kerberos security cluster, HDFS permission have been set by default (umask is set to 027), without configuration and service restart.
non-Kerberos security cluster, a configuration must be added and the service must be restarted.
umask value can be modified as needed.
HDFS is a basic service, and Hive/HBase are based on HDFS. Therefore, HDFS permission control must be configured in advance when configuring other upper layer services.
When permissions are enabled for HDFS, the services must be set up (such as /spark-history for spark, and /tmp/$user/ for yarn).
Sticky bit can be set for a folder to prevent users other than superuser/file owner/dir owner from deleting files/folders in the folder (even if other users have rwx permissions on the folder). For example:
#That is, adding numeral 1 as the first digit
hadoop fs -chmod 1777 /tmp
hadoop fs -chmod 1777 /spark-history
hadoop fs -chmod 1777 /user/hive/warehouse