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Oracle® Big Data Appliance Owner's Guide
Release 2 (2.1)

Part Number E40655-03
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12 Using the dcli Utility

The dcli utility executes commands across a group of servers on Oracle Big Data Appliance and returns the output. You use dcli in Chapter 7.

This chapter contains the following sections:

12.1 Overview of the dcli Utility

The dcli utility executes commands on multiple Oracle Big Data Appliance servers using the administrative (eth0) interface to make the connections. You can run the utility from any server.

12.1.1 Setting Up Passwordless SSH

The dcli utility requires a passwordless Secure Shell (SSH) between the local server and all target servers. You run the dcli utility on the local server, and the commands specified in dcli execute on the target servers.

Two scripts facilitate the use of SSH on Oracle Big Data Appliance: setup-root-ssh and remove-root-ssh. These scripts accept two options that are also used by dcli:

  • -C: Targets all the servers in a Hadoop cluster

  • -g: Targets a user-defined set of servers

See Table 12-1 for details about these options.

To set up passwordless SSH for root: 

  1. Connect to an Oracle Big Data Appliance server using PuTTY or a similar utility. Select an SSH connection type.

  2. Log in as root.

  3. Set up passwordless SSH for root across the rack:

    setup-root-ssh
    

    You see the message "ssh key added" from each server.

  4. You can now run any ssh command on any server in the rack without entering a password. In addition to dcli commands, you can use scp to copy files between servers.

  5. To remove passwordless SSH from root:

    remove-root-ssh
    

See Also:

Full parameter descriptions of setup-root-ssh and remove-root-ssh.

12.1.2 Basic Use of dcli

This topic identifies some basic options to the dcli command. For a complete list of options, see Table 12-1.

12.1.2.1 Getting Help

To see the dcli help page, enter the dcli command with the -h or --help options. You can see a description of the commands by entering the dcli command with no options.

12.1.2.2 Identifying the Target Servers

You can identify the servers where you want the commands to run either in the command line or in a file. For a list of default target servers, use the -t option. To change the target servers for the current command, use the -c or -g options described in Table 12-1.

You can manually create files with groups of servers to manage together. For example, you might manage servers 5 to 18 together, because they have no special functions like servers 1 to 4.

12.1.2.3 Specifying the Commands

You typically specify a command for execution on the target servers on the command line. However, you can also create a command file for a series of commands that you often use together or for commands with complex syntax. See the -x option in Table 12-1.

You can also copy files to the target servers without executing them by using the -f option.

12.1.2.4 Controlling the Output Levels

You can request more information with the -v option or less information with the -n option. You can also limit the number of returned lines with the --maxlines option, or replace matching strings with the -r option.

Following are examples of various output levels using a simple example: the Linux date command.

Note:

The output from only one server (node07) is shown. The syntax in these examples executes the date command on all servers.

This is the default output, which lists the server followed by the date.

# dcli date
bda1node07-adm.example.com: Tue Feb 14 10:22:31 PST 2012

The minimal output returns OK for completed execution:

# dcli -n date
OK: ['bda1node07.example.com']

Verbose output provides extensive information about the settings under which the command ran:

dcli -v dateoptions.nodes: Noneoptions.destfile: Noneoptions.file: Noneoptions.group: dcserversoptions.maxLines: 100000options.listNegatives: Falseoptions.pushKey: Falseoptions.regexp: Noneoptions.sshOptions: Noneoptions.scpOptions: Noneoptions.dropKey: Falseoptions.serializeOps: Falseoptions.userID: rootoptions.verbosity 1options.vmstatOps Noneoptions.execfile: Noneargv: ['/opt/oracle/bda/bin/dcli', '-g', 'dcservers', '-v', 'date']Success connecting to nodes: ['bda1node07.example.com']...entering thread for bda1node07.example.com:execute: /usr/bin/ssh -l root bda1node07.example.com ' date' ...exiting thread for bda1node07.example.com status: 0bda1node07.example.com: Tue Feb 14 10:24:43 PST 2012]

12.2 dcli Syntax

dcli [options] [command]

Parameters 

options

The options described in Table 12-1. You can omit all options to run a command on all servers in the current rack.

command

Any command that runs from the operating system prompt. If the command contains punctuation marks or special characters, then enclose the command in double quotation marks.

The backslash (\) is the escape character. Precede the following special characters with a backslash on the command line to prevent interpretation by the shell. The backslash is not needed in a command file. See the -x option for information about command files.


$ (dollar sign)
' (quotation mark)
< (less than)
> (greater than)
( ) (parentheses)

Table 12-1 dcli Options

Option Description

-c nodes

Specifies a comma-separated list of Oracle Big Data Appliance servers where the command is executed

-C

Uses the list of servers in /opt/oracle/bda/cluster-rack-infiniband as the target. See "Identifying the Target Servers".

-d destfile

Specifies a target directory or file name for the -f option

-f file

Specifies files to be copied to the user's home directory on the target servers. The files are not executed. See the -l option.

-g groupfile

Specifies a file containing a list of Oracle Big Data Appliance servers where the command is executed. You can use either server names or IP addresses in the file.

-h, --help

Displays a description of the commands

-k

Pushes the ssh key to each server's /root/.ssh/authorized_keys file. See "Setting Up Passwordless SSH" for an easier alternative.

-l userid

Identifies the user ID for logging in to another server. The default ID is root.

--maxlines=maxlines

Identifies the maximum lines of output displayed from a command executed on multiple servers. The default is 10,000 lines.

-n

Abbreviates the output for non-error messages. Only the server name is displayed when a server returns normal output (return code 0).

You cannot use the -n and -r options together.

-r regexp

Replaces the output with the server name for lines that match the specified regular expression

-s sshoptions

Specifies a string of options that are passed to SSH

--scp=scpoptions

Specifies a string of options that are passed to Secure Copy (SCP), when these options are different from sshoptions

--serial

Serializes execution over the servers. The default is parallel execution.

-t

Lists the target servers

--unkey

Drops the keys from the authorized_key files of the target servers

-v

Displays the verbose version of all messages

--version

Displays the dcli version number

--vmstat=VMSTATOPS

Displays the syntax of the Linux Virtual Memory Statistics utility (vmstat). This command returns process, virtual memory, disk, trap, and CPU activity information.

To enter a vmstat command, enclose its options in quotation marks. For example:

--vmstat="-a 3 5"

See your Linux documentation for more information about vmstat.

-x execfile

Specifies a command file to be copied to the user's home directory and executed on the target servers. See the -l option.


12.3 dcli Return Values

  • 0: The command ran successfully on all servers.

  • 1: One or more servers were inaccessible or remote execution returned a nonzero value. A message lists the unresponsive servers. Execution continues on the other servers.

  • 2: A local error prevented the command from executing.

If you interrupt the local dcli process, then the remote commands may continue without returning their output or status.

12.4 dcli Examples

Following are examples of the dcli utility.

This example returns the default list of target servers:

# dcli -t
Target nodes: ['bda1node01-adm.example.com', 'bda1node02-adm.example.com', 'bda1node03-adm.example.com', 'bda1node04-adm.example.com', 'bda1node05-adm.example.com', 'bda1node06-adm.example.com', 'bda1node07-adm.example.com', 'bda1node08-adm.example.com', 'bda1node09-adm.example.com']

The next example checks the temperature of all servers:

# dcli 'ipmitool sunoem cli "show /SYS/T_AMB" | grep value'

bda1node01-adm.example.com: value = 22.000 degree C
bda1node02-adm.example.com: value = 22.000 degree C
bda1node03-adm.example.com: value = 22.000 degree C
bda1node04-adm.example.com: value = 23.000 degree C
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