lamboot



LAMBOOT(1)                         LAM TOOLS                        LAMBOOT(1)




NAME

       lamboot - Start a LAM multicomputer.


SYNTAX

       lamboot [-b] [-d] [-h] [-H] [-l] [-s] [-v] [-V] [-x] [-nn] [-np] [-c
              <conf file>] [-prefix </lam/install/path/>] [-sessionprefix
              <value>] [-sessionsuffix <value>] [-withlamprefixpath <value>]
              [-ssi <key> <value>] [<bhost>]


OPTIONS

       -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 output.  This implies -v.

       -h      Print the command help menu.

       -l      Delay hostname-to-IP-address resolution.

       -prefix Use the LAM installation specified in </lam/install/path/>.
               Not compatible with LAM/MPI versions prior to 7.1.

       -s      Close stdio on the local node.

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

       -v      Be verbose.

       -x      Run in fault tolerant mode.

       -H      Do not display the command header.

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

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

       -session-prefix <value>
               Set the session prefix, overriding LAM_MPI_SESSION_PREFIX.

       -session-suffix <value>
               Set the session suffix, overriding LAM_MPI_SESSION_SUFFIX.

       -withlamprefixpath <value>
               Override the internal installation path.  For internal use on-
               ly, do not use unless you know what you are doing.


ENVIRONMENT VARIABLES

       LAM_MPI_SESSION_PREFIX

       LAM_MPI_SESSION_SUFFIX
                 It is possible to change the session directory used by
                 LAM/MPI, normally of the form:

       <tmpdir>/lam-<username>@<hostname>[-<suffix>]

       <tmpdir>  will be set to LAM_MPI_SESSION_PREFIX if set.  Otherwise, it
                 will fall back to the value of TMPDIR.  If neither of these
                 are set, the default is /tmp.

       <suffix>  can be overridden by the LAM_MPI_SESSION_SUFFIX environment
                 variable.  If LAM_MPI_SESSION_SUFFIX is not set and LAM is
                 running under a supported batch scheduling system, $suffix
                 will be a value unique to the currently running job.


DESCRIPTION

       The lamboot tool starts the LAM software on each of the machines speci-
       fied in the boot schema, <bhost>.  The boot schema specifies the host-
       names of nodes to be used in the run-time MPI environment, and option-
       ally lists how may CPUs LAM may used on each node.  The user may wish
       to first run the recon(1) tool to verify that LAM can be started.

       Starting LAM is a three step procedure.  In the first step, hboot(1) is
       invoked on each of the specified machines.  Then each machine allocates
       a dynamic port and communicates it back to lamboot which collects them.
       In the third step, lamboot gives each machine the list of ma-
       chines/ports in order to form a fully connected topology.  If any ma-
       chine was not able to start, or if a timeout period expires before the
       first step completes, lamboot invokes lamwipe(1) to terminate LAM and
       reports the error.

       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 speci-
       fied in the LAMBHOST environment variable.  Otherwise a default file,
       lam-bhost.def, is used.  LAM searches for <bhost> first in the local
       directory and then in the installation directory under etc/.

       In addition, lamboot uses a process schema for the individual LAM
       nodes.  A process schema (see conf(5)) is a description of the process-
       es which constitute the operating system on a node.  In general, the
       system administrator maintains this file -- LAM/MPI users will general-
       ly not need to change this file.  It is also possible for the user to
       customize the LAM software with a private process schema.

   The bhost file
       The format of the <bhost> file is documented in the bhost(5) man page.

       lamboot will resolve all names in <bhost> on the node in which lamboot
       was invoked (the origin node).  After that, LAM will only use IP ad-
       dresses, not names.  Specifically, the name resolution configuration on
       all other nodes is not used.  Hence, the the origin node must be able
       to resolve all the names in <bhost> to addresses that are reachable by
       all other nodes.

       A common mistake is to list localhost (or any name that resolves to the
       special address 127.0.0.1 -- the loopback TCP/IP device) in a <bhost>
       file that contains other nodes.  In this case, the address 127.0.0.1
       would be sent to each of the other nodes as the address of the origin
       node.  If the other nodes try to use 127.0.0.1 to contact the origin
       node, they will actually be contacting themselves, and would eventually
       timeout and fail.

       The IP addresses obtained from <bhost> are used for LAM’s meta mes-
       sages: startup and shutdown of jobs, out-of-band messages used for co-
       ordination, etc.  The amount of traffic is fairly low (unless using the
       "lamd" mode of MPI message passing, in which case all MPI traffic will
       also utilize LAM’s meta messages for transport -- see mpirun(1)).  When
       using the TCP RPI, these IP addresses are also used for MPI message
       passing via direct sockets between each pair of nodes.

       A common case is where a "master" node has multiple network interface
       cards (NICs) -- one that is connected to a public network, and one that
       is connected to a private network where parallel jobs are to be run.
       To include the master node in a <bhost> file, the IP name (or address)
       of the NIC on the private network should be listed in <bhost>.  This
       ensures that all the other nodes can reach the master node on the pri-
       vate network.

       As another example, some configurations have multiple TCP/IP NICs in
       each node of a parallel job.  One NIC is considered "slow" (e.g.,
       10Mbps), while the other is considered "fast" (e.g., 100Mbps).  It is
       desirable to allow LAM to take advantage of the higher bandwidth on the
       "fast" network for MPI messages.  As such, <bhost> should list the IP
       names (or addresses) of all the "fast" NICs.  However, if the LAM RPI
       does not use TCP/IP (e.g., the Myrinet/GM RPI), the <bhost> file should
       probably list the "slow" NICs so that LAM’s meta message traffic does
       not cause overhead and potentially detract from performance on the
       "fast" network from other high-performance applications.

   Delaying hostname lookups
       Normally, name resolution of hostnames is done on the machines where
       lamboot is invoked.  This is done for optimization reasons, so that the
       list of hostnames only needs to be resolved once (potentially minimiz-
       ing the amount of DNS or other hostname-lookup network traffic).

       However, in some non-uniform networking environments, this is not suf-
       ficient because each host may have a different IP address on each of
       its peers.  For example, host A may have address Z on host B, but have
       address Y on host C.

       The -l option to lamboot will cause LAM to distribute hostnames to each
       node rather than a fully resolved set of IP addresses.  Hence, each
       node where LAM is booted will do its own name resolution on the list of
       hostnames.

   SSI (System Services Interface)
       The -ssi switch allows the passing of parameters to various SSI mod-
       ules.  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> ar-
       gument 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:

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

       lamboot -ssi boot rsh -ssi rsh_agent "ssh -x" boot_schema
           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 <value>s 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 correspond-
       ing environment variables before running lamboot.  The form of the en-
       vironment 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 en-
       vironment variable -- they are not checked (by lamwipe) for correct-
       ness.  Illegal or incorrect <value> arguments may or may not be report-
       ed -- it depends on the specific SSI module.

   Remote Executable Invocation
       All tweakable aspects of launching executables on remote nodes during
       lamboot 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.

   Closing stdio
       The stdio of each LAM daemon on a remote host that is launched by lam-
       boot is closed by default.  Normally, the stdio of the LAM daemon
       launched on the local host is left open so that the internal LAM tst-
       dio(3) package works properly.  However, it is sometimes desirable to
       close the stdio of the local LAM daemon as well.  For example:

          rsh somenode lamboot -s hostfile

       This is because rsh waits for two conditions before exiting: lamboot to
       exit, and stdout / stderr to be closed.  Without -s, stdout / stderr
       would not be closed, and rsh (and ssh) will hang even though lamboot
       had completed.  -s causes the stdout / stderr of the local LAM daemon
       to be closed upon invocation, which will allow rsh to complete.  Using
       -s will not affect lamboot in any other way, but it will prevent the
       tstdio(3) package from working properly.

   Fault Tolerance
       If the -x option is given, LAM runs in fault tolerant mode.  In this
       mode, nodes exchange ‘‘heart beat’’ messages periodically to make sure
       all nodes are running and the links connecting them are operational.
       When a node’s heart beats stop, it is declared ‘‘dead’’ and all LAM
       nodes (and processes) are notified.  This allows users to write fault
       tolerant applications that can degrade gracefully, or fully recover by
       replacing the defunct node with another (see lamgrow(1)).  Since this
       mode introduces a performance penalty, it is not activated by default.


EXAMPLES

       lamboot -v
           Start LAM on the machines described in the default boot schema.
           Report about important steps as they are done.

       lamboot -d hostfile
           Start LAM on the machines described in file hostfile.  Provide in-
           credibly detailed reports on what is happening at each stage in the
           boot process.

       lamboot mynodes
           Start LAM on the machines described in the boot schema mynodes.
           Operate silently.


FILES

       laminstalldir/etc/lam-bhost.def   default boot schema file, where
                                         "laminstalldir" is the directory
                                         where LAM/MPI was installed

       laminstalldir/etc/lam-conf.lamd   default process schema file for LAM
                                         nodes


SEE ALSO

       recon(1), lamwipe(1), hboot(1), tstdio(3), bhost(5), conf(5), lam-help-
       file(5), lamssi(7), lamssi_boot(7)









LAM 7.1.1                       September, 2004                     LAMBOOT(1)

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