RSTARTD(1) MachTen Programmer’s Manual RSTARTD(1)

rstartd - a sample implementation of a Remote Start rsh


rstartd.real [-c configfilename]

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

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

-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.

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.

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

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

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

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

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:

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

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

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

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

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

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.

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.

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

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

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

All MISC values are passed unmodified as environment

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.

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

Jordan Brown, Quarterdeck Office Systems

X Version 11 Release 6 5