Shell Command Introduce

You can use the Hadoop Distributed File System (HDFS) Shell command to perform operations on the HDFS, such as reading and writing files.

To run the HDFS Shell:

Go to the directory of HDFS client and enter the command. An example is shown as follows:

cd /opt/client/HDFS/hadoop/bin

hdfs dfs -mkdir /tmp/input

You can run the following command to seek help about HDFS commands:

hdfs --help

For details about the shell, see

**Table 1** Transparent encryption-related commands
Scenario	Operation	Command	Description
hadoop shell command management key	Create keys.	hadoop key create <keyname> [-cipher <cipher>] [-size <size>] [-description <description>] [-attr <attribute=value>] [-provider <provider>] [-help]	The create subcommand creates a key for the name specified by the <keyname> argument within the provider specified by the -provider argument. You may specify a cipher with the -cipher argument. The default cipher is "AES/CTR/NoPadding" currently. The default keysize is 128. You may specify the requested key length using the -size argument. Arbitrary attribute=value style attributes may be specified using the -attr argument. The -attr may be specified for multiple times, once per attribute.
	Rollback	hadoop key roll <keyname> [-provider <provider>] [-help]	The roll subcommand creates a new version for the specified key within the provider indicated using the -provider argument.
	Delete keys	hadoop key delete <keyname> [-provider <provider>] [-f] [-help]	The delete subcommand deletes all versions of the key specified by the <keyname> argument within the provider specified by the -provider argument. The command asks for user confirmation unless -f is specified.
	View keys	hadoop key list [-provider <provider>] [-metadata] [-help]	The list subcommand displays the keynames contained in a particular provider as configured in core-site.xml or specified with the -provider argument. The -metadata argument displays the metadata.

**Table 2** Shell commands of Colocation client
Operation	Command	Description
Group creation	hdfs colocationadmin -createGroup -groupId <groupID> -locatorIds <comma separated locatorIDs> or -file <path of the file contains all of locatorIDs>	Used to create a group. In the command, groupID is the group name and locatorID is the locator name. You can enter comma-separated locator IDs using command lines. You can also write locator IDs into a file so that the system can obtain the locator IDs by reading the file.
Group deletion	hdfs colocationadmin -deleteGroup <groupID>	Used to delete the specified group.
Group query	hdfs colocationadmin -queryGroup <groupID>	Used to query details about a specified group, including locators in the group and information about each locator and its corresponding DataNode.
Viewing all groups	hdfs colocationadmin -listGroups	Used to list all groups and their creation time.
Setting ACL permissions on Colocation directories	hdfs colocationadmin -setAcl	Used to set ACL permissions on Colocation directories in ZooKeeper. The default root directory of Colocation in ZooKeeper is /hadoop/colocationDetails.