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NAME
     rstartd - a sample implementation  of  a  Remote  Start  rsh
     helper

SYNOPSIS
     rstartd

     rstartd.real [-c configfilename]

DESCRIPTION
     Rstartd is an implementation of a Remote Start  "helper"  as
     defined  in  "A  Flexible Remote Execution Protocol Based on
     rsh".

     This document describes the peculiarities of rstartd and how
     it is configured.

OPTIONS
     -c configfilename
             This option  specifies  the  "global"  configuration
             file  that rstartd is to read.  Normally, rstartd is
             a shell script that invokes rstartd.real with the -c
             switch, allowing local configuration of the location
             of  the  configuration  file.   If  rstartd.real  is
             started    without   the   -c   option,   it   reads
             <XRoot>/lib/X11/rstart/config, where <XRoot>  refers
             to the root of the X11 install tree.

INSTALLATION
     It is critical to successful interoperation  of  the  Remote
     Start  protocol  that  rstartd  be  installed in a directory
     which is in the "default" search path, so that  default  rsh
     requests and the ilk will be able to find it.

CONFIGURATION AND OPERATION
     Rstartd is by design highly configurable.   One  would  like
     things  like  configuration  file  locations to be fixed, so
     that  users  and  administrators  can  find   them   without
     searching,  but reality is that no two vendors will agree on
     where things should  go,  and  nobody  thinks  the  original
     location  is  "right".  Thus, rstartd allows one to relocate
     all of its files and directories.

     Rstartd has a hierarchy of  configuration  files  which  are
     executed in order when a request is made.  They are:

          global config
          per-user ("local") config
          global per-context config
          per-user ("local") per-context config
          config from request

     As you  might  guess  from  the  presence  of  "config  from
     request",  all  of  the config files are in the format of an
     rstart request.  Rstartd defines a few  additional  keywords
     with the INTERNAL- prefix for specifying its configuration.

     Rstartd starts by reading and executing  the  global  config
     file.   This file will normally specify the locations of the
     other configuration files and any systemwide defaults.

     Rstartd will then read the user's local config file, default
     name $HOME/.rstart.

     Rstartd will then start interpreting the request.

     Presumably one of the first lines in the request will  be  a
     CONTEXT line.  The context name is converted to lower case.

     Rstartd will read the global config file for  that  context,
     default name <XRoot>/lib/X11/rstart/contexts/<name>, if any.

     It will then read the user's config file for  that  context,
     default name $HOME/.rstart.contexts/<name>, if any.

     (If neither of these exists, rstartd aborts with  a  Failure
     message.)

     Rstartd will finish interpreting the  request,  and  execute
     the program specified.

     This allows the system administrator and the  user  a  large
     degree  of  control  over  the  operation  of  rstartd.  The
     administrator has final say, because the global config  file
     doesn't need to specify a per-user config file.  If it does,
     however, the user can  override  anything  from  the  global
     file,  and  can  even  completely replace the global context
     config files.

     The config files have a somewhat more flexible  format  than
     requests  do;  they  are  allowed to contain blank lines and
     lines beginning with "#" are comments and ignored.   (#s  in
     the middle of lines are data, not comment markers.)

     Any commands  run  are  provided  a  few  useful  pieces  of
     information  in  environment variables.  The exact names are
     configurable, but the supplied defaults are:

          $RSTART_CONTEXT          the name of the context
          $RSTART_GLOBAL_CONTEXTS  the global contexts directory
          $RSTART_LOCAL_CONTEXTS   the local contexts directory
          $RSTART_GLOBAL_COMMANDS  the global generic commands directory
          $RSTART_LOCAL_COMMANDS   the local generic commands directory

     $RSTART_{GLOBAL,LOCAL}_CONTEXTS should contain  one  special
     file,  @List,  which contains a list of the contexts in that
     directory in the format  specified  for  ListContexts.   The
     supplied  version  of  ListContexts will cat both the global
     and local copies of @List.

     Generic  commands  are  searched  for  in  several   places:
     (defaults)

          per-user per-context directory ($HOME/.rstart.commands/<context>)
          global per-context directory (<XRoot>/lib/X11/rstart/commands/<context>)
          per-user all-contexts directory ($HOME/.rstart.commands)
          global all-contexts directory (<XRoot>/lib/X11/rstart/commands)

     (Yes, this means you  can't  have  an  all-contexts  generic
     command  with  the  same  name as a context.  It didn't seem
     like a big deal.)

     Each of these directories should have a  file  called  @List
     that  gives  the  names  and descriptions of the commands in
     that    directory    in    the    format    specified    for
     ListGenericCommands.

CONFIGURATION KEYWORDS
     There are several  "special"  rstart  keywords  defined  for
     rstartd  configuration.   Unless  otherwise specified, there
     are no defaults; related features are disabled in this case.

     INTERNAL-REGISTRIES name ...
             Gives a space-separated list  of  "MISC"  registries
             that  this  system  understands.   (Registries other
             than this are accepted but generate a Warning.)

     INTERNAL-LOCAL-DEFAULT relative_filename
             Gives the name  ($HOME  relative)  of  the  per-user
             config file.

     INTERNAL-GLOBAL-CONTEXTS absolute_directory_name
             Gives  the  name   of   the   system-wide   contexts
             directory.

     INTERNAL-LOCAL-CONTEXTS relative_directory_name
             Gives the name  ($HOME  relative)  of  the  per-user
             contexts directory.

     INTERNAL-GLOBAL-COMMANDS absolute_directory_name
             Gives the name of the system-wide  generic  commands
             directory.

     INTERNAL-LOCAL-COMMANDS relative_directory_name
             Gives the name  ($HOME  relative)  of  the  per-user
             generic commands directory.

     INTERNAL-VARIABLE-PREFIX prefix
             Gives the prefix for the  configuration  environment
             variables rstartd passes to its kids.

     INTERNAL-AUTH-PROGRAM authscheme program argv[0] argv[1] ...
             Specifies   the   program   to   run   to   set   up
             authentication   for  the  specified  authentication
             scheme.  "program argv[0] ..." gives the program  to
             run  and its arguments, in the same form as the EXEC
             keyword.

     INTERNAL-AUTH-INPUT authscheme
             Specifies the data to be given to the  authorization
             program  as  its  standard  input.  Each argument is
             passed as a single line.  $n, where n is  a  number,
             is  replaced  by  the  n'th  argument  to  the "AUTH
             authscheme arg1 arg2 ..." line.

     INTERNAL-PRINT arbitrary text
             Prints its arguments as a Debug message.  Mostly for
             rstartd debugging, but could be used to debug config
             files.

NOTES
     When using the C shell, or any  other  shell  which  runs  a
     script  every  time the shell is started, the script may get
     run several times.  In the worst case, the  script  may  get
     run three times:

          By rsh, to run rstartd
          By rstartd, to run the specified command
          By the command, eg xterm

     rstartd currently limits lines, both from config  files  and
     requests, to BUFSIZ bytes.

     DETACH is implemented by redirecting file  descriptors  0,1,
     and 2 to /dev/null and forking before executing the program.

     CMD is implemented by invoking $SHELL (default /bin/sh) with
     "-c" and the specified command as arguments.

     POSIX-UMASK is implemented in the obvious way.

     The authorization programs are run in the  same  context  as
     the  target program - same environment variables, path, etc.
     Long term this might be a problem.

     In the X context, GENERIC-CMD Terminal runs xterm.   In  the
     OpenWindows context, GENERIC-CMD Terminal runs cmdtool.


     In the X context, GENERIC-CMD LoadMonitor  runs  xload.   In
     the   OpenWindows   context,  GENERIC-CMD  LoadMonitor  runs
     perfmeter.

     GENERIC-CMD ListContexts lists the contents of @List in both
     the  system-wide  and  per-user contexts directories.  It is
     available in all contexts.

     GENERIC-CMD ListGenericCommands lists the contents of  @List
     in   the  system-wide  and  per-user  commands  directories,
     including the per-context  subdirectories  for  the  current
     context.  It is available in all contexts.

     CONTEXT None is not implemented.

     CONTEXT Default is really dull.

     For installation  ease,  the  "contexts"  directory  in  the
     distribution  contains  a  file  "@Aliases"  which  lists  a
     context name and aliases for that  context.   This  file  is
     used   to   make  symlinks  in  the  contexts  and  commands
     directories.

     All  MISC  values  are  passed  unmodified  as   environment
     variables.

     One can mistreat rstartd in any number of ways, resulting in
     anything  from stupid behavior to core dumps.  Other than by
     explicitly running programs I don't think it  can  write  or
     delete  any  files,  but  there's no guarantee of that.  The
     important thing is that (a) it probably  won't  do  anything
     REALLY  stupid  and (b) it runs with the user's permissions,
     so it can't do anything catastrophic.

     @List files need not be complete; contexts or commands which
     are  dull or which need not or should not be advertised need
     not be listed.  In particular, per-user @List  files  should
     not  list  things  which are in the system-wide @List files.
     In the future, perhaps ListContexts and  ListGenericCommands
     will automatically suppress lines from the system-wide files
     when there are per-user replacements for those lines.

     Error handling is OK to weak.  In particular, no attempt  is
     made   to   properly  report  errors  on  the  exec  itself.
     (Perversely, exec errors could  be  reliably  reported  when
     detaching,  but not when passing the stdin/out socket to the
     app.)

     If compiled  with  -DODT1_DISPLAY_HACK,  rstartd  will  work
     around a bug in SCO ODT version 1.  (1.1?)  (The bug is that
     the X clients are all  compiled  with  a  bad  library  that
     doesn't  know  how to look host names up using DNS.  The fix
     is to look up a host name in $DISPLAY and substitute  an  IP
     address.)   This  is a trivial example of an incompatibility
     that rstart can hide.

SEE ALSO
     rstart(1), rsh(1),  A  Flexible  Remote  Execution  Protocol
     Based on rsh

AUTHOR
     Jordan Brown, Quarterdeck Office Systems

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