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@c This file is part of the Mailfromd manual.
@c Copyright (C) 2008 Sergey Poznyakoff
@c See file mailfromd.texi for copying conditions.
@c *******************************************************************
@cindex component, pies
  The name @command{pies} (pronounced @samp{p-yes}) stands for
@samp{Program Invocation and Execution Supervisor}.  This utility
starts and controls execution of external programs, called
@dfn{components}.  Each component is a stand-alone program, which is
executed in foreground.  Upon startup, @command{pies} reads the list
of components from its configuration file, starts them, and remains in
background, controlling their execution.  When any of the components
terminates, @command{pies} restarts it.  Its configuration allows to
specify actions other than simple restart, depending on the exit code
of the component.

@cindex prerequisite, pies
@cindex dependency, pies
@cindex dependents, pies
@anchor{component prerequisite}
  A component @samp{A} may depend on another components, say
@samp{B} and @samp{C}, i.e. require them to be running at the moment of its
startup.  Components @samp{B} and @samp{C} are called
@dfn{prerequisites} for @samp{A}, while @samp{A} is called a
@dfn{dependency} or @dfn{dependent} component of @samp{B}, @samp{C}.

  Before restarting any component, @command{pies} verifies if it is a
prerequisite for any other components.  If so, it first terminates its
dependencies, then restarts the component, and then starts its
dependencies again, in the order of their appearance in the
configuration file.

  The standard output and standard error streams of a component can be
redirected to a file or to an arbitrary @command{syslog} channel.

@anchor{init-style}
@cindex init-style components
  These way of operation applies to so-called @dfn{init-style}
components, called so because of the similarity with the
@command{init} process manager.  @command{Pies} is also able to handle
components that receive input on their @samp{stdin} and send reply to
@samp{stdout}.  Such components are called @dfn{inetd-style}
components.

@anchor{inetd-style}
@cindex inetd-style components
  Inetd-style components are not executed right after @command{pies}
startup.  Instead, @command{pies} opens a socket for each of them and
listens for connections on these sockets.  When a connection arrives,
it decides what component the socket corresponds to, and invokes this
component to service that connection.  In this case, the connection is
bound to component's @samp{stdin} and @samp{stdout} streams.  The
@samp{stderr} stream can be redirected to a file or to syslog, as
described above.  This mode of operation is similar to that of
@command{inetd} utility.

@anchor{meta1-style}
@cindex meta1-style components
@cindex smtps
  Third type of components, supported by @command{pies} are
@dfn{meta1-style} components.  As the name suggests this type is
designed expressly as a support for MeTA1 components, namely
@command{smtps}.  This type can be regarded as a mixture of the above
two.  For each meta1-style component @command{pies} opens a socket
after start-up, and then executes the component.  Once the component
is running, @command{pies} passes it the file descriptor of the
socket, using a preconfigured @acronym{UNIX}-style socket.  Further
handling of the socket is the responsibility of the component itself.

@anchor{accept-style}
@cindex accept-style components
  The last flavor of @command{pies} components are @dfn{accept-style}
components, which are handled basically as @samp{inetd-style} ones,
except that after binding to the socket @command{pies} immediately
starts the component, without waiting for an actual connection.

  Any number of components of all three styles can be handled
simultaneously.

  Components are started in the order of their appearance in the
configuration file and terminated in reverse order.  When starting or
stopping component dependencies, the same order is preserved.

  This order is reversed for files included by @code{include-meta1}
statement (@pxref{include-meta1}).

@menu
* Pies Configuration File::
* Component Statement::
* include-meta1::
* Global Configuration::
* Pies Debugging::
* Configuration Example::
* Command Line Usage::
* Pies Invocation::
@end menu

@node Pies Configuration File
@section Pies Configuration File
  @command{Pies} reads its configuration from the main Mailutils
configuration file.  @xref{configuration, Mailutils Configuration
File,, mailutils, GNU Mailutils Manual}, for a description of GNU
Mailutils configuration system.  It is recommended to use
@code{include @var{directory}} statement (@pxref{Include, Include
Statement,, mailutils, GNU Mailutils Manual}), and to place
@command{pies} configuration in file @file{@var{directory}/pies}.
@xref{MeTA1}, for an example.

The following standard Mailutils configuration statements are understood:

@multitable @columnfractions 0.3 0.6
@headitem Statement @tab Reference
@item debug @tab @xref{Debug Statement, Mailutils Debug Statement,,
mailutils, GNU Mailutils Manual}.
@item logging @tab @xref{Logging Statement, Mailutils Logging,,
mailutils, GNU Mailutils Manual}.
@item include @tab @xref{Include, Include Statements,,
mailutils, GNU Mailutils Manual}.
@item mailer  @tab @xref{Mailer, Mailer Statement,,
mailutils, GNU Mailutils Manual}.
@item acl     @tab @xref{ACL Statement, ACL Statement,,
mailutils, GNU Mailutils Manual}.
@end multitable

@node Component Statement
@section Component Statement
@kwindex component
  The @code{component} statement defines a new component:

@smallexample
component @var{tag} @{
  @dots{}
@}
@end smallexample

The component is identified by its @dfn{tag}, which is given as
argument to the @code{component} keyword.

@deffn {Pies Conf} mode @var{mode}
  Declare the type (style) of the component.  Accepted values for
@var{mode} are:

@table @asis
@item exec
@itemx wait
  Create an @samp{init-style} component (@pxref{init-style}).  This is
the default.
  
@item inetd
@itemx nostartaccept
  Create an @samp{inetd-style} component (@pxref{inetd-style}).
  
@item pass
@itemx pass-fd 
  Create a @samp{meta1-style} component (@pxref{meta1-style}).
  
@item accept
  Create a @samp{accept-style} component (@pxref{accept-style}).
@end table
@end deffn

@deffn {Pies Conf} program @var{name}
Full file name of the component binary.  This binary will be executed
(via @command{/bin/sh -c}) each time @command{pies} decides it needs
to start the component.

To supply command line arguments, use @code{command} statement.
@end deffn
  
@deffn {Pies Conf} command @var{string}
Command line for the program.  The argument should be just as
arguments normally are, starting with the name of the program.  The
latter may be different from the one specified to @code{program}
statement.  Its value will be available to the program as
@code{argv[0]}. 
@end deffn

@deffn {Pies Conf} disable @var{bool}
If @var{bool} is @samp{true}, this component is disabled,
i.e. @command{pies} will ignore it.
@end deffn

@deffn {Pies Conf} precious @var{bool}
@cindex precious components, pies
If @var{bool} is @samp{true}, this component is marked as precious.
Precious components are never disabled by @command{pies}, even if they
respawn too fast.
@end deffn
  

@menu
* Prerequisites::
* Component Privileges::
* Resources::
* Actions Before Startup::
* Exit Actions::
* Output Redirectors::
* Inetd-Style Components::
* Meta1-Style Components::
* Component Syntax Summary::
@end menu

@node Prerequisites
@subsection Component Prerequisites
@cindex declaring prerequisites
@cindex prerequisites, declaring
Prerequisites (@pxref{component prerequisite}) for a component are
declared using the following statement: 

@deffn {Pies Conf} prerequisites @var{tag-list}
The argument is either a list of component tags, @emph{defined before
this component}, or one of the following words:

@table @asis
@item all
Declare all components defined so far as prerequisites for this one.

@item none
No prerequisites.  This is the default.
@end table
@end deffn

  If you wish, you can define dependents, instead of prerequisites:

@deffn {Pies Conf} dependents @var{tag-list}
Declare dependents for this component.  @var{var-list} is a list of
component tags.
@end deffn

@node Component Privileges
@subsection Component Privileges
@cindex privileges, pies
  Following statements control the privileges with which the component
is executed.

@deffn {Pies Conf} user @var{user-name}
Start component with the UID and GID of this user. 
@end deffn

@deffn {Pies Conf} group @var{group-list}
Retain supplementary groups, specified in @var{group-list}.
@end deffn

@deffn {Pies Conf} allgroups @var{bool}
Retain all supplementary groups of which user, given with
@command{user} statement, is a member.  This is the default for
components specified in @file{meta1.conf} file (@pxref{include-meta1}).
@end deffn

@node Resources
@subsection Resources

@deffn {Pies Conf} limits @var{string}
Impose limits on system resources, as defined by @var{string}.  The
argument consists of @dfn{commands}, optionally separated by any
amount of whitespace.  A command is a single command letter followed
by a number, that specifies the limit.  The command letters are
case-insensitive and coincide with those used by the shell @code{ulimit}
utility:

@multitable @columnfractions 0.3 0.6 
@headitem Command @tab  The limit it sets
@item     A       @tab  max address space (KB)
@item     C       @tab  max core file size (KB)
@item     D       @tab  max data size (KB)
@item     F       @tab  maximum file size (KB)
@item     M       @tab  max locked-in-memory address space (KB)
@item     N       @tab  max number of open files
@item     R       @tab  max resident set size (KB)
@item     S       @tab  max stack size (KB)
@item     T       @tab  max CPU time (MIN)
@item     U       @tab  max number of processes
@item     P       @tab  process priority -20..20 (negative = high priority)
@end multitable

For example:

@smallexample
limits T10 R20 U16 P20
@end smallexample

Additionally, the command letter @samp{L} is recognized.  It is
reserved for future use (@samp{number of logins} limit) and is ignored
in version @value{VERSION}.
@end deffn

@deffn {Pies Conf} umask @var{number}
Set the umask.  The @var{number} must be an octal value not greater
than @samp{777}.  The default umask is inherited at startup.
@end deffn

@deffn {Pies Conf} env @var{args}
Set program environment.

Arguments are a whitespace-delimited list of specifiers.  The
following specifiers are understood: 

@table @asis
@item - (a dash)
Clear the environment.  This is understood only when used as a first
word in @var{args}.

@item -@var{name}
Unset the environment variable @var{name}.

@item -@var{name}=@var{val}
Unset the environment variable @var{name} only if its value is @var{val}.

@item @var{name}
Retain the environment variable @var{name}.

@item @var{name}=@var{value}
Define environment variable @var{name} to have given @var{value}.

@item @var{name}+=@var{value}
Retain variable @var{name} and append @var{value} to its existing
value.  If no such variable is present in the environment, it is
created and @var{value} is assigned to it.  However, if @var{value}
begins with a punctuation character, this character is removed from it
before the assignment.  This is convenient for using this construct with
environment variables like @env{PATH}, e.g.:

@smallexample
PATH+=:/sbin
@end smallexample

In this example, if @env{PATH} exists, @samp{:/sbin} will be appended
to it.  Otherwise, it will be created and @samp{/sbin} will be
assigned to it.

@item @var{name}=+@var{value}
Retain variable @var{name} and prepend @var{value} to its existing
value.  If no such variable is present in the environment, it is
created and @var{value} is assigned to it.  However, if @var{value}
ends with a punctuation character, this character is removed from it
before assignment. 
@end table
@end deffn

@node Actions Before Startup
@subsection Actions Before Startup

  Several statements are available that specify actions to perform
immediately before starting the component:

@deffn {Pies Conf} chdir @var{dir}
Change to the directory @var{dir}.
@end deffn

@deffn {Pies Conf} remove-file @var{file-name}
Remove @var{file-name}.  This is useful, for example, to remove stale
@acronym{UNIX} sockets or pid-files, which may otherwise prevent the
component from starting normally.

As of version @value{VERSION} only one @command{remove-file} may be given.
@end deffn

@deffn {Pies Conf} settle-timeout @var{number}
Wait @var{number} seconds.  This is kind of kludge.  Currently it is
used for components imported from @file{meta1.conf} file
(@pxref{include-meta1}), where @code{settle-timeout 1} is implied.
This may change in future versions.
@end deffn

@node Exit Actions
@subsection Exit Actions
@kwindex return-code
  The default behavior of @command{pies} if an @samp{init-style}
component terminates is to restart it.  Unless the component
terminates with 0 exit code, a corresponding error message is issued
to the log file.  This behavior can be modified using
@code{return-code} statement:

@smallexample
return-code @var{codes} @{
  @dots{}
@}
@end smallexample

  Its argument is a list of exit codes.  Exit codes can be specified
as decimal numbers, or as symbolic code names from the table below:

@multitable @columnfractions 0.5 0.3
@headitem Name       @tab Numeric value
@item EX_OK          @tab 0 
@item EX_USAGE       @tab 64
@item EX_DATAERR     @tab 65
@item EX_NOINPUT     @tab 66
@item EX_NOUSER      @tab 67
@item EX_NOHOST      @tab 68
@item EX_UNAVAILABLE @tab 69
@item EX_SOFTWARE    @tab 70
@item EX_OSERR       @tab 71
@item EX_OSFILE      @tab 72
@item EX_CANTCREAT   @tab 73
@item EX_IOERR       @tab 74
@item EX_TEMPFAIL    @tab 75
@item EX_PROTOCOL    @tab 76
@item EX_NOPERM      @tab 77
@item EX_CONFIG      @tab 78
@end multitable

  If the component exits with an exit code listed in @var{codes},
@command{pies} executes actions specified by its substatements.  These
are:

@deffn {Pies Conf} action @samp{disable | restart}
If @samp{restart} is given, restart the component.  This is the
default.  Otherwise, mark the component and as disabled.  Component
dependents are stopped and marked as disabled as well.  Disabled
components are never started, unless requested by the administrator.
@end deffn

@deffn {Pies Conf} notify @var{email-string}
Send an email notification to addresses in @var{email-string}.  The
latter is a comma-separated list of email addresses, e.g.:

@smallexample
notify "root@@localhost,postmaster@@localhost";
@end smallexample

The @code{mailer} statement (@pxref{Mailer, Mailer Statement,,
mailutils, GNU Mailutils Manual}) configures the mailer used to send
the message.  The message itself is configured by the @code{message}
statement.
@end deffn

@deffn {Pies Conf} message @var{string}
Supply notification message text to use by @code{notify} statement.
@var{String} must be a valid RFC 822 message text, i.e. it must begin
with message headers, followed by an empty line and actual message
body.

The following macro-variables are expanded within @var{string}:

@multitable @columnfractions 0.5 0.5
@headitem Variable @tab Expansion
@item canonical-program-name @tab @samp{pies}
@item program-name @tab Program name of the @command{pies} binary.
@item package    @tab Package name (@samp{Mailfromd}).
@item version    @tab Package version (@value{VERSION}).
@item mu-version @tab Version of GNU Mailutils.
@item component  @tab Name of the terminated component.
@item retcode    @tab Component exit code, in decimal.
@end multitable

If @code{message} statement is not given, the following default
message is used instead:

@smallexample
From: <>
X-Agent: $@{canonical-program-name@} ($@{package@} $@{version@})
Subject: Component $@{component@} terminated with code $@{retcode@}.

@end smallexample
@end deffn

  Any number of @code{return-code} statements are allowed, provided
that their @var{codes} do not intersect.

  Such statements can also be used outside of @code{component} block.
In this case, they supply global actions, i.e. actions applicable to
all components.  The @code{return-code} statements appearing within a
@code{component} block override the global ones.

@node Output Redirectors
@subsection Output Redirectors
@cindex repeater
  Output redirectors allow to redirect standard error and/or standard
output of a component to a file or @command{syslog} facility.

@deffn {Pies Conf} stderr @var{type} @var{channel}
@deffnx {Pies Conf} stdout @var{type} @var{channel}
Redirect standard error (if @code{stderr}) or standard output (if
@code{stdout}) to the given channel.

The type of redirection is specified by @var{type} argument:

@table @asis
@item file
Redirect to file.  In this case @var{channel} gives the full name of
the file.  For example:

@smallexample
stderr file /var/log/component/name.err;
@end smallexample

@item syslog
Redirect to the syslog channel.  The syslog priority is given by the
@var{channel} argument.  Its allowed values are: @samp{emerg},
@samp{alert}, @samp{crit}, @samp{err}, @samp{warning}, @samp{notice},
@samp{info}, @samp{debug}.  The facility is inherited from the
@code{logging} statement (@pxref{Logging Statement, Mailutils Logging,,
mailutils, GNU Mailutils Manual}), or from @code{facility} statement
(see below), if given.

Example:

@smallexample
stderr syslog err;
@end smallexample
@end table
@end deffn

@deffn {Pies Conf} facility @var{syslog-facility}
Specify the syslog facility to use in syslog redirectors.  Allowed 
values for @var{syslog-facility} are: @samp{user}, @samp{daemon},
@samp{auth}, @samp{authpriv}, @samp{mail}, @samp{cron}, @samp{local0}
through @samp{local7} (all names case-insensitive), or a facility number.
@end deffn

@node Inetd-Style Components
@subsection Inetd-Style Components
@cindex inetd-style components
  Inetd-style components are declared using @code{mode inetd}
statement.  You must also declare a socket to listen for requests for
such components:

@anchor{inetd-socket}
@deffn {Pies Conf} socket @var{url}
Define a socket to listen on.  Allowed values for @var{url} are:

@table @asis
@item file name
Specifies a @acronym{UNIX} socket file name.  You may use a relative
file name, provided that @code{chdir} statement is used for this
component (@pxref{Actions Before Startup, chdir}).

@item local://@var{file}[;@var{args}]
@itemx file://@var{file}[;@var{args}]
@itemx unix://@var{file}[;@var{args}]
Listen on a @acronym{UNIX} socket file @var{file}, which may be either
absolute or relative file name, as described above.  Optional
arguments @var{args} control ownership and file mode of @var{file}.  They
are a list of assignments, separated by semicolons.  The following
values are allowed:

@table @asis
@item user
User name of the socket owner.

@item group
Owner group of the socket, if it differs from the @code{user} group.

@item mode
Socket file mode (octal number between @samp{0} and @samp{777}).

@item umask
Umask to use when creating the socket (octal number between @samp{0}
and @samp{777}). 
@end table

For example:

@smallexample
socket unix:/var/run/socket;user=nobody;group=mail;mode=770
@end smallexample

@item inet://@var{ip}:@var{port}
Listen on IPv4 address @var{ip} (may be given as a symbolic host name),
on port @var{port}.
@end table

Notice, that @command{pies} version @value{VERSION} handles only
@acronym{TCP} sockets and only IPv4 addresses.  Support for IPv6 will
be added in future versions.  Support for @acronym{UDP} sockets will
be added if there is a demand.
@end deffn

@node Meta1-Style Components
@subsection Meta1-Style Components
@cindex meta1-style components
  Meta1-style components are declared using @code{mode pass}
statement.  For such components, you must declare both a socket to
listen on (@pxref{inetd-socket} and a @acronym{UNIX} socket name to
pass the file descriptor to the component.  The latter is defined
using @code{pass-fd-socket} statement:

@deffn {Pies Conf} pass-fd-socket @var{file-name}
The argument is an absolute or relative file name of the socket file.
In the latter case, the @code{chdir @var{dir}} statement must be used
for this component (@pxref{Actions Before Startup, chdir}), and the
socket will be looked under @var{dir}.

This socket file is supposed to be created by the component binary
upon its startup.
@end deffn

@node Component Syntax Summary
@subsection Component Syntax Summary
  This subsection summarizes the @code{component} summary.  For each
statement, a reference to its detailed description is supplied.

@smallexample
component @var{tag} @{
  # @r{Component execution mode.}
  # @xref{Component Statement, mode}.
  mode @samp{exec | wait | accept | inetd | nostartaccept | pass-fd | pass};
  
  # @r{Full name of the program.}
  # @xref{Component Statement, program}.
  program @var{name};
  # @r{Command line.}
  # @xref{Component Statement, command}.
  command @var{string};
  
  # @r{Disable this entry.}
  # @xref{Component Statement, disable}.
  disable @var{bool};
  # @r{Mark this entry as precious.}
  # @xref{Component Statement, precious}.  
  precious @var{bool};
  
  # @r{List of prerequisites.}
  # @xref{Prerequisites}.
  prerequisites (@var{compnames});
  # @r{List of components for which this one is a prerequisite.}
  # @xref{Prerequisites, dependents}.
  dependents (@var{compnames});
  
  # @r{Listen on the given url.}
  # @xref{Inetd-Style Components}.
  socket @var{url};
  
  # @r{Pass fd through this socket.}
  # @xref{Meta1-Style Components}.
  pass-fd-socket @var{soket-name};
  
  # @r{ACL for this component.}
  # @xref{ACL Statement, ACL Statement,, mailutils, GNU Mailutils Manual}.
  acl @{ @dots{} @}
  
  # @r{Override default syslog facility for this component.}
  facility @var{facility};
  # @r{Redirect program's standard output to the given}
  # @r{file or syslog priority.}
  # @xref{Output Redirectors}.
  stdout @samp{file | syslog} @var{channel};
  # @r{Redirect program's standard error to the given}
  # @r{file or syslog priority.}
  # @xref{Output Redirectors}.
  stderr @samp{file | syslog} @var{channel};
  
  # @r{Run with this user privileges.}
  # @xref{Component Privileges}.
  user @var{user-name};
  # @r{Retain supplementary group.}
  # @xref{Component Privileges, group}.
  group @var{group-name};
  # @r{Retain all supplementary groups of which user is a member.}
  # @xref{Component Privileges, allgroups}.
  allgroups @var{bool};
  
  # @r{Set system limits.}
  # @xref{Resources}.
  limits @var{string};
  
  # @r{Force this umask.}
  # @xref{Resources, umask}.
  umask @var{number};
  
  # @r{Set program environment.}
  # @xref{Resources, env}.
  env @var{assignments};
  
  # @r{Change to this directory before executing the component.}
  # @xref{Actions Before Startup, chdir}.
  chdir @var{dir};
  # @r{Remove @var{file-name} before starting the component.}
  # @xref{Actions Before Startup, remove-file}.
  remove-file @var{file-name};
  # @r{Time to wait before starting this component.}
  # @xref{Actions Before Startup, settle-timeout}.
  settle-timeout @var{number};
  
  # @r{Actions:}
  # @xref{Exit Actions}.
  return-code @var{exit-code-list} @{
    # @r{Action to take when a component finishes with this return code.}
    action @samp{disable | restart};
    # @r{Notify these addresses when then component terminates.}
    notify @var{email-string};
    # @r{Notification message text (with headers).}
    message @var{string};
  @}
@}
@end smallexample

@node include-meta1
@section Using MeTA1 Configuration File
@cindex /etc/meta1/meta1.conf
  @command{Pies} is able to take list of components from MeTA1
configuration file:

@deffn {Pies Conf} include-meta1 @var{file}
Parse @var{file} as MeTA1 configuration file and incorporate
components defined there into the current component list.

For example:

include-meta1 /etc/meta1/meta1.conf;
@end deffn

Thus, you can use @command{pies} instead of the default MeTA1 program
manager @command{mcp}. 

To ensure compatibility with MeTA1, the components read from MeTA1
configuration are started in reverse order (i.e. from last to first),
and stopped in order of their appearance in @var{file}.  Of course,
this does not affect normal @command{pies} components.

The following @command{pies} statements are silently applied to
all MeTA1 components:

@smallexample
allgroups yes;
stderr file @var{compname}.log
chdir @var{queue-dir}
@end smallexample

Here, @var{compname} stands for the name of the component, and
@var{queue-dir} stands for the name of MeTA1 queue directory.  The
latter is @file{/var/spool/meta1} by default.  It can be changed using
the following statement

@deffn {Pies Conf} meta1-queue-dir @var{dir}
Set name of MeTA1 queue directory.
@end deffn

To override any default settings for a MeTA1 component, add a
@code{command} section with the desired settings after including
@file{meta1.conf}.  For example, here is how to redirect program
diagnostics to @samp{local1.debug} syslog channel:

@smallexample
include-meta1 /etc/meta1/meta1.conf

component smtps @{
  facility local1;
  stderr syslog debug;
@}
@end smallexample

@node Global Configuration
@section Global Configuration
The statements described in this section affect @command{pies}
behavior as a whole.

@deffn {Pies Conf} umask @var{number}
Set the default umask.  The @var{number} must be an octal value not greater
than @samp{777}.  The default umask is inherited at startup.
@end deffn

@deffn {Pies Conf} limits @var{arg}
Set global system limits for all pies components.  @xref{Resources,
limits}, for a detailed description of @var{arg}.
@end deffn

@deffn {Pies Conf} return-code @{ ... @}
Configure global exit actions.  @xref{Exit Actions}, for a detailed
description of this statement.
@end deffn

@deffn {Pies Conf} shutdown-timeout @var{number};
Wait @var{number} of seconds for all components to shut down.
Default is 5 seconds.
@end deffn

@menu
* Less Useful Statements::
@end menu

@node Less Useful Statements
@subsection Less Useful Statements

  Some configuration file statements are provided for completeness and
are rarely, if at all used.  If used improperly, they may severely
impair the functionality of @command{pies} or even render it
useless.  Do not use them, unless you have a good knowledge of
@command{pies} internals and understand their impact.

  The following three statements define file names of various files
needed by @command{pies}.  Use them only if the defaults does not
suit your needs:

@deffn {Pies Conf} pidfile @var{file}
Write PID of the master @command{pies} process to @var{file}.  By
default, master PID is stored in @file{@var{statedir}/pies.pid}
(@pxref{statedir}). 
@end deffn

@deffn {Pies Conf} control-file @var{file}
Set file name of the @command{pies} control file.  Default is
@file{@var{statedir}/pies.ctl} 
@end deffn

@deffn {Pies Conf} stat-file @var{file}
Set file name of the statistics output file.  Default is
@file{@var{statedir}/pies.stat}. 
@end deffn

  Normally, @command{pies} must be run with root privileges.  If,
however, you've found an implementation for it, that requires another
privileges, you may change them using the following three statements:

@command{pies} process.  
@deffn {Pies Conf} user @var{user-name}
Start @command{pies} with the UID and GID of this user. 
@end deffn

@deffn {Pies Conf} group @var{group-list}
Retain supplementary groups, specified in @var{group-list}.
@end deffn

@deffn {Pies Conf} allgroups @var{bool}
Retain all supplementary groups of which user, given with
@command{user} statement, is a member.  
@end deffn

@node Pies Debugging
@section Pies Debugging
  The amount of debugging information produced by @command{pies} is configured
using two configuration statements.  First of all, the standard
@code{debug} block statement controls debugging of the underlying GNU
Mailutils libraries (@pxref{Debug Statement, Mailutils Configuration
File,, mailutils, GNU Mailutils Manual}).  Secondly, the @code{debug}
statement controls debugging output of the @command{pies} utility
itself.

@deffn {Pies Conf} debug @var{spec}
Set debugging level for the @command{pies} code.  @xref{Debug
Statement, Mailutils Configuration File,, mailutils, GNU Mailutils
Manual}, for a description of @var{spec} syntax.  The following
debugging levels are used:

@table @asis
@item trace1
Log all basic actions: starting and stopping of components, received incoming
@acronym{TCP} connections, sending mails.  Notify about setting
limits.  Log pre-startup actions (@pxref{Actions Before Startup}).

@item trace2
Log setting particular limits.  Log recomputing alarms.

@item trace4
Dump execution environments

@item trace6
Debug the parser of MeTA1 configuration grammar.

@item trace7
Debug the lexical analyzer of MeTA1 configuration file.
@end table
@end deffn

@node Configuration Example
@section Configuration Example
  In this section we provide several examples of working @command{pies}
configuration files.

@menu
* Simple Pies::
* Hairy Pies::
* Inetd Pies::
@end menu

@node Simple Pies
@subsection Simplest Case: Using Pies to Run Pmult
  The example below runs @command{pmult} (@pxref{pmult}) utility with
the privileges of @samp{meta1} user.  Both standard error and standard
output are redirected to syslog facility @samp{mail}, priorities
@samp{err} and @samp{info}, correspondingly.

@smallexample
component pmult @{
  command "/usr/local/sbin/pmult";
  user meta1s;
  facility mail;
  stderr syslog err;
  stdout syslog info;
@}
@end smallexample

@node Hairy Pies
@subsection Using Pies to Run Pmult and MeTA1
  The example below is a working configuration file for running
@command{pmult} and all components of MeTA1, configured in
@file{/etc/meta1/meta1.conf}.  The global @code{return-code} statement
is used to configure @command{pies} behavior for some exit codes.

@smallexample
# Sample pies configuration for running pmult and MeTA1

# Special handling for exit codes that mean the program was
# incorrectly used or misconfigured.
return-code (EX_USAGE, EX_CONFIG) @{
  action disable;
  notify "root";
  message <<- EOT
    From: Pies <>
    X-Agent: $@{canonical-program-name@} ($@{package@} $@{version@})
    Subject: Component $@{component@} disabled.
    
    Component "$@{component@}" has terminated with code $@{retcode@},
    which means it encountered some configuration problem.
    I will not restart it automatically. Please fix its configuration
    and restart it manually at your earliest convenience.
    
    To restart, run ``$@{program-name@} -R $@{component@}''
    ---
    Wuff-wuff,
    Pies
  EOT;
@}

component pmult @{
  command "/usr/local/sbin/pmult";
  user meta1s;
  stderr syslog err;
  stdout syslog info;
@}

include-meta1 "/etc/meta1/meta1.conf";
@end smallexample

@node Inetd Pies
@subsection Running Pies Instead of Inetd

This configuration file allows to run @command{pies} instead of
@command{initd}.  It starts two services: @samp{ftp} and @samp{pop3d},
and restricts access to them to two local subnets:

@smallexample
acl @{
   log from any "Connect from $@{address@}";
   allow from 10.10.10.0/24;
   allow from 192.168.10.0/27;
   deny from any;
@}

debug "<trace4";

component ftp @{
   mode inetd;
   socket "inet://0.0.0.0:21";
   umask 027;
   program /usr/sbin/ftpd
   command ftpd -l -C;
@}

component pop3d @{
   mode inetd;
   socket "inet://0.0.0.0:110";
   program "/usr/sbin/pop3d";
   command "pop3d --inetd";
@}
@end smallexample

@node Command Line Usage
@section Command Line Usage

  When run without arguments, @command{pies} parses and loads the
configuration file, detaches itself from the controlling terminal
(becomes a daemon), and starts all components.  Before actually
starting up, it ensures that no another instance of it is 
already running, by looking for a PID file and verifying that the PID
listed there is alive and responding.  If another instance is running,
@command{pies} refuses to start up.

@anchor{pies-status}
  After startup, you can verify the status of the running process
using @option{--status} command line option:

@smallexample
$ pies --status
redirector smtps/stderr 4697
redirector pmult/stderr 4677
redirector pmult/stdout 4676
component pmult 4678 /usr/local/sbin/pmult
component smar 4680 smar -f /etc/meta1/meta1.conf -d 100
component qmgr 4691 qmgr -f /etc/meta1/meta1.conf
component smtpc 4696 smtpc -f /etc/meta1/meta1.conf
component smtps 4698 smtps -d100 -f /etc/meta1/meta1.conf
@end smallexample

  In its output, lines beginning with @samp{component} refer to
running components.  For running components, the following information
is displayed:

@enumerate 1
@item Component tag (@pxref{Component Statement}).
@item PID of the running instance of the component.
@item Command line of the component, as set by the @code{command}
statement (@pxref{Component Statement, command}).
@end enumerate

If the component is not running, the reason is indicated in the PID
column, between the square brackets, e.g.:

@smallexample
component pmult [disabled; scheduled for Mon 01 Dec 2008 20:27:02] 
  /usr/local/sbin/pmult
@end smallexample

@noindent
(the example above is split in two lines for readability).

@anchor{pies-restart}
  You can restart any component by using the
@option{--restart-component} (@option{-R}) option, e.g.:

@smallexample
$ pies -R pmult smtps
@end smallexample

  To stop all running components and shut down @command{pies}, use the
@option{--stop} (@option{-S}) command line option:

@smallexample
$ pies --stop
@end smallexample

@cindex dependencies, pies
@anchor{dump-depmap}
@cindex --dump-depmap option, pies
  Two options are provided for verifying inter-component
dependencies.  The @option{--dump-depmap} option prints on the
standard output the @dfn{dependency map}.  This map is a square table
where rows represent dependents and columns represent prerequisites.
An @samp{X} sign is placed on each crossing which corresponds to the
actual dependency.  For example:

@smallexample
$ pies --dump-depmap
Dependency map:
    0  1  2  3  4
 0                
 1                
 2     X          
 3        X       
 4     X  X       

Legend:
 0: pmult
 1: smar
 2: qmgr
 3: smtpc
 4: smtps
@end smallexample

This example corresponds to the configuration file shown in @ref{Hairy
Pies}.  To illustrate how to read it, consider the 4th row of the
table.  According to the legend, number 4 means @samp{smtps}
component.  There are two @samp{X} marks: in columns 1 and 2.  This
means that @samp{smtps} depends on @samp{smar} and @samp{qmgr}.

@anchor{dump-prereq}
@cindex --dump-prereq option, pies
  You can also list prerequisites explicitly:

@smallexample
$ pies --dump-prereq
qmgr: smar
smtpc: qmgr
smtps: smar qmgr
@end smallexample

@node Pies Invocation
@section Pies Invocation

@table @option
@item --force
Force startup even if another instance may be running.

@item --foreground
Remain in foreground.

@item --stderr
Log to standard error.

@item --syslog
Log to syslog.  This is the default.

@item -x @var{level}
@itemx --debug=@var{level}
Set debug verbosity level.  @xref{Pies Debugging}, for a description
of @var{level}.

@item -r
@itemx --reload
@itemx --hup
Reload the running instance of pies.

@item -R
@itemx --restart-component
Restart components named in the command line.  @xref{pies-restart}.

@item -s
@itemx --status
Display info about the running instance.  @xref{pies-status}.

@item -S
@itemx --stop
Stop the running instance.  

@item --dump-depmap
Dump dependency map.  @xref{dump-depmap}.

@item --dump-prereq
Dump prerequisite charts.  @xref{dump-prereq}.

@end table

Apart from these, the common GNU Mailutils options are understood, which
are useful for checking @command{pies} configuration file for syntax
errors.  @xref{Common Options, Common Options, , mailutils, GNU
Mailutils Manual}, for a detailed description of these.

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