recon - Online in the Cloud

PROGRAM:

NAME

recon - Check if LAM can be started.

SYNOPSIS

recon [-a] [-b] [-d] [-h] [-v] [-nn] [-np] [-ssi key value] [bhost]

OPTIONS

-a Report all host errors.

-b Assume local and remote shell are the same. This means that only one remote shell
invocation is used to each node. If -b is not used, two remote shell invocations
are used to each node.

-d Turn on debugging.

-h Print the command help menu.

-ssi key value
Send arguments to various SSI modules. See the "SSI" section, below.

-v Be verbose.

-nn Don't add "-n" to the remote agent command line

-np Do not force the execution of $HOME/.profile on remote hosts

DESCRIPTION

In order for LAM to be started on a remote UNIX machine, several requirements have to be
fulfilled:

1) The machine must be reachable via the network.

2) The user must be able to remotely execute on the machine with the default remote
shell program that was chosen when LAM was configured. This is usually rsh(1), but
any remote shell program is acceptable (such as ssh(1), etc.). Note that remote
host permission must be configured such that the remote shell program will not ask
for a password when a command is invoked on remote host.

3) The remote user's shell must have a search path that will locate LAM executables.

4) The remote shell's startup file must not print anything to standard error when
invoked non-interactively.

If any of these requirements is not met for any machine declared in bhost, LAM will not be
able to start. By running recon first, the user will be able to quickly identify and
correct problems in the setup that would inhibit LAM from starting.

The local machine where recon is invoked must be one of the machines specified in bhost.

The bhost file is a LAM boot schema written in the host file syntax. See bhost(5).
Instead of the command line, a boot schema can be specified in the LAMBHOST environment
variable. Otherwise a default file, bhost.def, is used. LAM seaches for bhost first in
the local directory and then in the installation directory under etc/.

recon tests each machine defined in bhost by attempting to execute on it the tkill(1)
command using its "pretend" option (no action is taken). This test, if successful,
indicates that all the requirements listed above are met, and thus LAM can be started on
the machine. If the attempt is successful, the next machine is checked. In case the
attempt fails, a descriptive error message is displayed and recon stops unless the -a
option is used, in which case recon continues checking the remaining machines.

If recon takes a long time to finish successfully, this will be a good indication to the
user that the LAM system to be started has slow communication links or heavily loaded
machines, and it might be preferable to exclude or replace some of the machines in the
system.

SSI (System Services Interface)
The -ssi switch allows the passing of parameters to various SSI modules. LAM's SSI
modules are described in detail in lamssi(7). SSI modules have direct impact on MPI
programs because they allow tunable parameters to be set at run time (such as which boot
device driver to use, what parameters to pass to that driver, etc.).

The -ssi switch takes two arguments: key and value. The key argument generally specifies
which SSI module will receive the value. For example, the key "boot" is used to select
which RPI to be used for starting processes on remote nodes. The value argument is the
value that is passed. For example:

recon -ssi boot tm
Tells LAM to use the "tm" boot module for native launching in PBSPro / OpenPBS
environments (the tm boot module does not require a boot schema).

recon -ssi boot rsh -ssi rsh_agent "ssh -x" boot_file
Tells LAM to use the "rsh" boot module, and tells the rsh module to use "ssh -x" as
the specific agent to launch executables on remote nodes.

And so on. LAM's boot SSI modules are described in lamssi_boot(7). This page should be
consulted for specific actions that are taken by, and how to tweak the run-time behavior
of each boot module.

The -ssi switch can be used multiple times to specify different key and/or value
arguments. If the same key is specified more than once, the values are concatenated with
a comma (",") separating them.

Note that the -ssi switch is simply a shortcut for setting environment variables. The
same effect may be accomplished by setting corresponding environment variables before
running lamboot. The form of the environment variables that LAM sets are:
LAM_MPI_SSI_key=value.

Note that the -ssi switch overrides any previously set environment variables. Also note
that unknown key arguments are still set as environment variable -- they are not checked
(by lamwipe) for correctness. Illegal or incorrect value arguments may or may not be
reported -- it depends on the specific SSI module.

Remote Executable Invocation
All tweakable aspects of launching executables on remote nodes during recon are discussed
in lamssi(7) and lamssi_boot(7). Topics include (but are not limited to): discovery of
remote shell, run-time overrides of the agent use to launch remote executables (e.g., rsh
and ssh), etc.

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