Host File Options

  As we stated earlier, only one person at a site needs to install PVM, but each PVM user can have his own hostfile, which describes his own personal virtual machine.

The hostfile   defines the initial configuration of hosts that PVM combines into a virtual machine. It also contains information about hosts that you may wish to add to the configuration later.

The hostfile in its simplest form is just a list of hostnames one to a line. Blank lines are ignored, and lines that begin with a # are comment lines. This allows you to document the hostfile and also provides a handy way to modify the initial configuration by commenting out various hostnames.

# configuration used for my run
sparky
azure.epm.ornl.gov
thud.cs.utk.edu
sun4

Figure: Simple hostfile listing virtual machine configuration

Several options can be specified on each line after the hostname. The options are separated by white space.

lo= userid

allows you to specify an alternative login name for this host; otherwise, your login name on the start-up machine is used.

so=pw

will cause PVM to prompt you for a password on this host. This is useful in the cases where you have a different userid and password on a remote system. PVM uses rsh by default to start up remote pvmd's, but when pw is specified, PVM will use rexec() instead.

dx= location of pvmd

allows you to specify a location other than the default for this host. This is useful if you want to use your own personal copy of pvmd,

ep= paths to user executables

allows you to specify a series of paths to search down to find the requested files to spawn on this host. Multiple paths are separated by a colon. If ep= is not specified, then PVM looks in $HOME/pvm3/bin/PVM_ARCH for the application tasks.

sp= value

specifies the relative computational speed of the host compared with other hosts in the configuration. The range of possible values is 1 to 1000000 with 1000 as the default.

bx= location of debugger

specifies which debugger script to invoke on this host if debugging is requested in the spawn routine.
Note: The environment variable PVM_DEBUGGER can also be set. The default debugger is pvm3/lib/debugger.

wd= working_directory

specifies a working directory in which all spawned tasks on this host will execute. The default is $HOME.

ip= hostname

specifies an alternate name to resolve to the host IP address.

so=ms

specifies that a slave pvmd will be started manually on this host. This is useful if rsh and rexec network services are disabled but IP connectivity exists. When using this option you will see in the tty of the pvmd3

        [t80040000] ready   Fri Aug 27 18:47:47 1993
        *** Manual startup ***
        Login to "honk" and type:
        pvm3/lib/pvmd -S -d0 -nhonk 1 80a9ca95:0cb6 4096 2 80a95c43:0000
        Type response:

On honk, after typing the given line, you should see

        ddpro<2312> arch<ALPHA> ip<80a95c43:0a8e> mtu<4096>

which you should relay back to the master pvmd. At that point, you will see

        Thanks

and the two pvmds should be able to communicate.

If you want to set any of the above options as defaults for a series of hosts, you can place these options on a single line with a * for the hostname field. The defaults will be in effect for all the following hosts until they are overridden by another set-defaults line.

Hosts that you don't want in the initial configuration but may add later can be specified in the hostfile by beginning those lines with an &. An example hostfile displaying most of these options is shown in Figure .

# Comment lines start with a # (blank lines ignored)
gstws
ipsc dx=/usr/geist/pvm3/lib/I860/pvmd3
ibm1.scri.fsu.edu lo=gst so=pw

# set default options for following hosts with *
* ep=$sun/problem1:~/nla/mathlib
sparky
#azure.epm.ornl.gov
midnight.epm.ornl.gov

# replace default options with new values
* lo=gageist so=pw ep=problem1
thud.cs.utk.edu
speedy.cs.utk.edu

# machines for adding later are specified with &
# these only need listing if options are required
&sun4   ep=problem1
&castor dx=/usr/local/bin/pvmd3
&dasher.cs.utk.edu lo=gageist
&elvis  dx=~/pvm3/lib/SUN4/pvmd3

Figure: PVM hostfile illustrating customizing options

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