The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
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File Makefile 284 bytes 2023-01-29 20:53:10
File README 11482 bytes 2023-01-29 20:53:10

    1 $FreeBSD$
    2 
    3        README file, for the boot config file setup.  This is meant
    4        to explain how to manage the loader configuration process.
    5        The boot and loading process is either defined, or being
    6        defined in boot(8) and loader(8).
    7 
    8        The ongoing development of the FreeBSD bootloader, and its
    9        rapid deployment while still in the development phase, has
   10        resulted in a large number of installations with outdated
   11        configurations.  Those installations actively tracking the
   12        FreeBSD development should also ensure that their bootloader
   13        configurations are updated.  If you see files discussed here
   14        that your system doesn't yet have, add them yourself.
   15 
   16        This is an effort to give the currently correct method for
   17        setting up your boot process.  It includes information on
   18        setting up screen savers and plug and play information, and
   19        also on recording any changes you make in your kernel
   20        configuration.  This file is temporary, because as I noted,
   21        the process is still undergoing development, and will still
   22        change.  Man pages are coming out, but they're still going
   23        to be somewhat fragile for a while.  If you note anything in
   24        here that's broken, it would be a good idea to report it to
   25        the FreeBSD-current list, or to Daniel C. Sobral
   26        <dcs@FreeBSD.org> or Mike Smith <msmith@FreeBSD.org>.
   27 
   28        NOTE:
   29 
   30        Please understand, all this is very current development, and
   31        while getting this working for STABLE is a goal, it's not
   32        yet ready for that.  It's possible that parts of this might
   33        indeed work for stable, but if you're not absolutely sure
   34        what you're doing, you're better off not using the
   35        information in this README for STABLE.  Use this for current
   36        only for a while longer, please!
   37 
   38        After the first two stages in the booting process (described
   39        in boot(8)), the last stage of the booting process, called
   40        the loader (see loader(8)) reads in the /boot/loader.rc
   41        file.  The two lines you should have there are:
   42 
   43        include /boot/loader.4th
   44        start
   45 
   46        This reads the ficl (forth) initialization files, then
   47        /boot/default/loader.conf.  This file, which strongly
   48        resembles in form /etc/rc.conf but functions quite
   49        differently, has spots for endless user customization but
   50        isn't yet completely finished.  For one thing, it used to
   51        assume a /kernel.config instead of a /boot/kernel.conf.
   52        Watch the first few lines of /boot/defaults/loader.conf to
   53        see if the file name changes.
   54 
   55        [See the section at the end on loader.conf syntax]
   56 
   57        You don't actually want to make any changes to
   58        /boot/defaults/loader.conf, the file that is a  hacking-
   59        target is:
   60 
   61        /boot/loader.conf
   62 
   63        and might very likely not exist yet on your system).  You
   64        should copy /boot/defaults/loader.conf to /boot/loader.conf,
   65        and then cut out anything you didn't want changed.
   66 
   67        The start command also loads your kernel for you, so don't
   68        put any lines in there like "load kernel", they'll fail (but
   69        really have already worked for you).  Start also reads in
   70        the file /boot/defaults/loader.conf and /boot/loader.conf.
   71        If you don't have /boot/loader.conf, you'll see a message on
   72        boot about it, but it's a warning only, no other effects.
   73        See the section on loader.conf syntax at the end of this
   74        document, for some more pointers on loader.conf syntax.
   75 
   76        The best way to manage splash screens is with entries in
   77        /boot/loader.conf, and this is very clearly illustrated in
   78        /boot/defaults/loader.conf (which you could just copy over
   79        to /boot/loader.conf).  I'm going to illustrate here how you
   80        *could* do it in /boot/loader.rc (for information only)
   81        but I don't recommend you do this; use the
   82        /boot/defaults/loader.conf syntax, it's easier to get it
   83        correct.
   84 
   85        You can load your splash screen by putting the following
   86        lines into /boot/loader.rc:
   87 
   88        load splash_bmp
   89        load -t splash_image_data /path/to/file.bmp
   90 
   91        The top line causes the splash_bmp module to get loaded.
   92        The second line has the parameter "-t" which tells the
   93        loader that the class of DATA being loaded is not a module,
   94        but instead a splash_image_data located in file
   95        /path/to/file.bmp.
   96 
   97        To get your plug and play data correctly set, run kget,
   98        redirecting the output to /boot/kernel.conf.  Note that kget
   99        right now adds an extra "q" to it's output (from the q for
  100        quit you press when you exit config), and if you want, you
  101        can remove that from the file.  Kget reports data only, so
  102        feel free to run it, just to see the output.  Make certain
  103        you have the kernel option USERCONFIG set in your kernel, so
  104        that you can do a boot -c, to initially set your cards up.
  105        Then, edit /boot/loader.conf so that the following line
  106        shows up (overwriting, in effect, a similar line in
  107        /boot/default/loader.conf):
  108 
  109        userconfig_script_load="YES"
  110 
  111        My own pnp line looks like:
  112        pnp 1 0 os irq0 15 irq1 0 drq0 1 drq1 0 port0 1332
  113        (kget changes numbers from hexadecimal to decimal).  Note
  114        that, at this moment, the change from using /kernel.config
  115        to using /boot/kernel.conf as the storage place for kernel
  116        config changes is going on.  Take a look at your
  117        /boot/defaults/loader.conf, see what's defined as
  118        userconfig_script_name, and if you override, make sure the
  119        file exists.  Note that the loader only has access to the
  120        root filesystem, so be careful where you tell it to read
  121        from.
  122 
  123 
  124           o If you interrupt autoboot, you'll engage interactive
  125             mode with loader. Everything you type will have the
  126             same effects as if it were lines in /boot/loader.rc.
  127 
  128           o While in interactive mode, you can get help by typing
  129             "?", "help [<topic> [<subtopic>]]" and "help index".
  130             These are mostly commands one would expect a normal
  131             user to use. I recommend you play with them a little,
  132             to gain further familiarity with what's going on.
  133 
  134             Note that it is not possible to damage or corrupt your
  135             system while experimenting with the loader, as it
  136             cannot write to any of your filesystems.
  137 
  138           o The command "unload" will unload everything. This is
  139             very useful.  Once loader.rc has finished and the
  140             system is in the autoboot count-down, you will usually
  141             have the kernel and other modules loaded. Now, suppose
  142             your new /kernel is broken, how do you load
  143             /kernel.old? By typing:
  144 
  145                  unload
  146                  load kernel.old
  147                  [any other modules you wish to load]
  148                  boot
  149 
  150           o If you use loader.conf, you can do:
  151 
  152                  unload
  153                  set kernel=kernel.old
  154                  boot-conf
  155 
  156             this will then load all the modules you have
  157             configured, using kernel.old as kernel, and boot.
  158 
  159           o From loader, you can use the command "more" to read the
  160             contents of /boot/loader.rc, if you wish. This is not
  161             FreeBSD's more. It is one of loader's builtin commands.
  162             Useful if you can't quite recall what you have there.
  163             :-) Of course, you can use this command to read
  164             anything else you want.
  165 
  166           o "boot -flag" works, "boot kernelname" works, "boot
  167             -flag kernelname" doesn't. "boot kernelname -flag"
  168             might work, but I'm not sure. The problem is that these
  169             flags are kernel's flags, not boot's flags.
  170 
  171           o There are a number of variables that can be set. You
  172             can see them in loader.conf, but you can get much more
  173             detailed information using the "help" command, eg. help
  174             set <variablename>.
  175 
  176           o The variable root_disk_unit is particularly important,
  177             as it solves a relatively common problem. This problem
  178             shows when the BIOS assign disk units in a different
  179             way than the kernel. For example, if you have two IDE
  180             disks, one on the primary, the other on the secondary
  181             controller, and both as master, the default in most
  182             kernels is having the first as wd0, and the second as
  183             wd2. If your root partition is in wd2, you'll get an
  184             error, because the BIOS sees these disks as 0 and 1
  185             (well, 1 and 2), and that's what loader tells the
  186             kernel. In this case, "set root_disk_unit=2" solves the
  187             problem.  You use this whenever the kernel fails to
  188             mount to root partition because it has a wrong unit
  189             number.
  190 
  191        FILE OVERVIEW
  192 
  193 
  194           o /boot/defaults/loader.conf -- Master configuration
  195             file, not to be edited.  Overridden by
  196             /boot/loader.conf.
  197 
  198           o /boot/loader.conf -- local system customization file,
  199             in form very much like /boot/defaults/loader.conf.
  200             This file is meant to be used by local users and the
  201             sysinstall process.
  202 
  203           o /boot/loader.conf.local -- local installation override
  204             file.  This is intended for use by installations with
  205             large numbers of systems, to allow global policy
  206             overrides.  No FreeBSD tools should ever write this
  207             file.
  208 
  209           o /kernel.config -- old location of kernel configuration
  210             changes (like pnp changes).
  211 
  212           o /boot/kernel.conf -- new location for kernel
  213             configuration changes.
  214 
  215           o /boot/loader.rc -- loader initial configuration file,
  216             chiefly used to source in a forth file, and start the
  217             configuration process.
  218 
  219        NOTES ON LOADER.CONF SYNTAX
  220 
  221        I'm copy here from the last 11 lines from
  222        /boot/defaults/loader.conf:
  223 
  224        ##############################################################
  225        ###  Module loading syntax example  ##########################
  226        ##############################################################
  227 
  228        #module_load="YES"              # loads module "module"
  229        #module_name="realname"         # uses "realname" instead of "module"
  230        #module_type="type"             # passes "-t type" to load
  231        #module_flags="flags"           # passes "flags" to the module
  232        #module_before="cmd"            # executes "cmd" before loading module
  233        #module_after="cmd"             # executes "cmd" after loading module
  234        #module_error="cmd"             # executes "cmd" if load fails
  235 
  236        The way this works, the command processor used by the loader
  237        (which is a subset of forth) inspects  these  variables  for
  238        their  suffix,  and  the  7  lines  above illustrate all the
  239        currently defined suffixes, and their use.   Take  the  part
  240        before  the  underscore,  and customize it i(make it unique)
  241        for your particular use, keeping the  suffix  to  allow  the
  242        particular function you want to activate.  Extra underscores
  243        are fine, because it's only the  sufixes  that  are  scanned
  244        for.
  245 
  246 
  247 
  248        (authors Chuck Robey and Daniel Sobral).

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