mach_init.tproj/mach_init.8

   1 .\" Copyright (c) 2002, Apple Computer, Inc.  All rights reserved.
   2 .\"
   3 .Dd March 20, 2002
   4 .Dt MACH_INIT 8
   5 .Os "Mac OS X"
   6 .Sh NAME
   7 .Nm mach_init
   8 .Nd Mach service naming (bootstrap) daemon
   9 .Sh SYNOPSIS
  10 .Nm mach_init
  11 .Op Fl D
  12 .Op Fl d
  13 .Op Fl F
  14 .Op Fl r Ar name-in-existing-server
  15 .Sh DESCRIPTION
  16 .Nm mach_init
  17 is a daemon that maintains various mappings between service names and
  18 the Mach ports that provide access to those services.  Clients of mach_init
  19 can register and lookup services, create new mapping subsets, and
  20 associate services with declared servers.  The mach_init daemon will
  21 also be responsible for launching (and/or re-launching) those service
  22 providing servers when attempts to use one or more of the associated services
  23 is detected.
  24 .Pp
  25 The options are as follows:
  26 .Bl -tag -width Ds
  27 .It Fl D
  28 When the
  29 .Fl D
  30 option is specified,
  31 .Nm mach_init
  32 starts in normal (non-debug) mode.  This is the default.
  33 .It Fl d
  34 When the
  35 .Fl d
  36 option is specified,
  37 .Nm mach_init
  38 starts in debug mode.
  39 .It Fl F
  40 When the
  41 .Fl F
  42 option is specified,
  43 .Nm mach_init
  44 forks during initialization so that it doesn't have to be put in
  45 the background manually by the caller.
  46 .It Fl r
  47 Using the
  48 .Fl r
  49 option tells
  50 .Nm mach_init
  51 to register itself in a previously running copy of
  52 .Nm mach_init
  53 under the service name
  54 .Ar name-in-existing-server.
  55 This is most useful when debugging new instances of
  56 .Nm mach_init
  57 itself, but can also be used for robustness or to allow the subsequent
  58 .Nm mach_init
  59 processes to run as a non-root user.  As mach_init is often used to
  60 launch servers, this could be more secure.  However,
  61 .Nm mach_init
  62 will not allow a server declaration to specify a user id different
  63 than that of the requesting client (unless the client is running as root).
  64 So it shouldn't be required for a secure configuration.
  65 .El
  66 .Pp
  67 Access to
  68 .Nm mach_init
  69 is provided through the bootstrap series of RPC APIs
  70 over service ports published by mach_init itself. Each Mach task has
  71 an assigned bootstrap port retrieved via task_get_bootstrap_port().
  72 These bootstrap port registrations are inherited across fork().
  73 .Pp
  74 The service registrations are grouped into subsets, providing a level
  75 of security. Only processes with access to the subset's bootstrap port
  76 will be able to register/lookup Mach ports within that subset.  Lookups
  77 from within a subset will search the subset first, then move on to its
  78 parent, and then its grand-parent, etc... until a string name match is
  79 found or the top of the bootstrap tree is reached.  Subsets are sometimes
  80 associated with login sessions to protect session-specific ports from being
  81 exposed outside the session.
  82 .Pp
  83 The first instance of
  84 .Nm mach_init
  85 is responsible for launching the traditional BSD process control initialization
  86 daemon (/sbin/init).
  87 .Sh SAMPLE USAGE
  88 .Pp
  89 mach_init -d -r com.company.bootstrap
  90 .Pp
  91 .Nm mach_init
  92 will start in debug mode, and register itself in an already running
  93 instance of
  94 .Nm mach_init
  95 under the service name com.company.bootstrap.
  96 .Sh NOTE
  97 .Pp
  98 Sending a SIGHUP to a running mach_init will toggle debug mode.
  99 .Sh SEE ALSO
 100 .Xr init 8