sangkilc / ocloud

oCloud: controlling cloud nodes via command lines (written in OCaml)

oCloud

oCloud is a command-line interface for managing cloud nodes. You can run arbitrary commands such as bash scripts on multiple cloud nodes from a terminal.

Quick Start

Usage: ./ocloud.native <client file> [optional args] <cmds>

The first argument of oCloud is always a client file, which specifies a list of client addresses. The second argument is an optional argument, which we will discuss later. The third (or the second if the optional argument is not given) argument and the rest of the arguments specify commands. You can list available commands by simply typing:

$ ./ocloud.native

Client File

A client file is an ASCII text file where each line specifies a tuple (client name, client address). Each line of the client file is separated by a colon ':', and there can be either two or three colon-separated elements. There are two elements when a line contains a client name and a client address. There are three elements when a line has a client name, an address, and a port number. Any line started with a '#' is considered to be a comment line. The following is an example of a client file, where there are three client nodes with names 01, 02 and 03.

### client name : client address : port (optional)
01 : hello-world.com
02 : hello-world.com : 4242
03 : foo-bar.net

List Clients (list)

The command list shows a list of client nodes and their connection statuses. Below is an example output. Notice we cannot connect to the node 03 in this case.

$ ./ocloud.native clients.txt list
(01) : (hello-world.com) : (22) : ok
(02) : (hello-world.com) : (4242) : ok
(03) : (foo-bar.net) : (22) : failed to connect

Always make sure all the client nodes are accessible before executing any commands. If you cannot connect to any of the nodes, please check the followings.

• Can you ping the nodes?
• Can you connect to the nodes by manually typing ssh?
• Did you ran ssh-agent? oCloud always assumes that ssh-agent is running on background, and properly setup so that you don't need to type in passphrases every time you invoke a command.
• Do you have a different user id in your client nodes than the one you have in your local machine? If so, set an environment variable OCLOUD_USER to have a correct user name for your remote machines.

Execution (exec)

The command exec executes (an) arbitrary command(s) in each client in parallel.

• Print out /tmp/results from each node:

$ ./ocloud.native clients.txt exec cat /tmp/results

• Grep the last foo line of /tmp/results from each node:

$ ./ocloud.native clients.txt exec 'grep foo /tmp/results | tail -n 1'

Root Execution (rootexec)

The command rootexec is the same as exec except that it executes commands as a root.

Push (push)

The commnand push copies a local file over to the client nodes in parallel.

• Copy myfile.txt to each client node (in /home/user/myfile.txt)

$ ./ocloud.native clients.txt push myfile.txt /home/user/myfile.txt

Pull (pull)

The commnand pull copies remote files of the same path into local.

• Copy /home/user/myfile.txt file on each node into results directory. The results directory will contain a list of directories for each client and each of the directory will contain myfile.txt that is copied from each of the client.

$ ./ocloud.native clients.txt pull /home/user/myfile.txt results