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yaboot.conf - Configuration file format used by yaboot(8) and



yaboot.conf - Configuration file format used by yaboot(8) and ybin(8).




The yaboot.conf file is a configuration file for yaboot which is read during booting, and for ybin(8) to generate a boot menu and to properly install yaboot onto the bootstrap(8) partition.
yaboot.conf provides instructions for yaboot. This includes which kernels to load and what options to pass to them. yaboot reads and parses its configuration file found on the bootstrap(8) partition on PowerMacs, and directly from the root filesystem on IBM PowerPC hardware. On PowerMacs you must run the ybin(8) command each time you modify /etc/yaboot.conf.
yaboot is able to boot kernels even without this configuration file or if this file is crippled or contains syntax errors, but the user has to enter full OpenFirmware names and full path of the images to load and all options required for them manually.


The file consists of comments and variable assignments.
Start with a # character, and continue to the end of the line.
Flag variables
Consist of a single keyword and are followed by whitespace or the end of the file.
String variables
Consist of the variable name, optional whitespace, a = character, optional whitespace, the value and required newline. IMPORTANT: ybin(8) specific options do not support embedded spaces. It is important that there be no trailing whitespace at the end of a line.
File names
Some string variables are expecting file names. A file name format in yaboot is:



[<devicename>][<part>][ [<m>-<n>]]
The first form refers to a file or directory on some supported filesystem (currently ext2, hfs, hfs+ or iso9660), the latter refers to a range of 512B blocks on a device. For a device block range, either <devicename>, or <part>, or [<m>-<n>] must be given.
Optional <devicename> is the OpenFirmware name of the device the file or range is located on. See below for its syntax. For OpenFirmware the device name must be immediately followed by the : character. The default is the boot device yaboot was booted from, or the value of device= in /etc/yaboot.conf.
Optional <part> is the 1 based partition number on the device. First partition is 1 (e.g. on /dev/sda in Linux is this /dev/sda1). The default is the default partition (the value of the partition variable in the config file). Note that on Apple partition tables the first partition is always the partition table itself (/dev/sda1 is the partition table).
<absolute_pathname> must start with a / character and is the pathname from the root of the filesystem on that device (unless it is the root filesystem this is different to the pathname you will see in GNU/Linux).
<m> is the first block number (in blocksize 512 bytes) of the range to be loaded and <n> is the last block number plus one.
Device name syntax is:

<fully_qualified_prom_device_name>[ :<part_number>]
where the fully qualified OpenFirmware device name starts with a / character for the root of the OpenFirmware device tree and contains all the nodes from the root in the tree up to the disk device node. If some node contains more than one child node with the same name and the path has to go through such node, a @ character followed by hexadecimal address pair is desirable to resolve the ambiguity. Optional partition number is a number that follows the : character 1 (for first partition) 2 (for second, partition, etc). OpenFirmware device names might look like:

OpenFirmware device names if specified as part of the file name (see above) should be followed by the : character to separate the device name from the optional Linux partition number, as shown above. For more information on this topic, consult bootstrap(8).
OpenFirmware also has some predefined aliases which are used instead of the longer canonical device names. Standard aliases include:

hd: - The primary master IDE hard disk.
ultra1: - The primary slave IDE hard disk.
cd: - The secondary master device (usually CDROM).
zip: - The secondary slave device (usually zip drive).
Variable names are case sensitive, values of string variables are also case sensitive.
Blanks and equal signs may only be part of a variable name or a value if they are escaped by a backslash or if the value is embedded in double quotes. An equal sign may not be the only character in a name or value.
An escaped tab is converted to an escaped blank. An escaped newline is removed from the input stream. An escaped backslash (i.e. two backslashes) is converted to a backslash. Inside quoted strings, only double quotes, backslashes and newlines can be escaped.

# Simple yaboot.conf
# End of global variables - begin image labels
This file contains options for two distinct programs: the ybin(8) (and mkofboot(8)) bootstrap(8) installer, and the yaboot(8) bootloader, each ignores the other's configuration options.
The ybin/mkofboot options are: boot= ofboot= install= magicboot= delay= bsd= macos= macosx= darwin= defaultos= usemount mntpoint= fstype= hfstype= nobless hide protect nonvram enablecdboot enablenetboot enableofboot brokenosx
The remaining options belong to yaboot(8).


/etc/yaboot.conf begins with a possibly empty global options section. This section contains all variable assignments up to the first image setting.
The following global options are recognized:
Specifies the bootstrap(8) partition ybin(8) will install the boot loader on. This partition needs to have an HFS or MSDOS filesystem created on it (except on IBM hardware). ybin(8) will not create a filesystem. If a filesystem is not present run mkofboot(8) instead of ybin(8) for the first time. The bootstrap(8) partition must have a partition type of Apple_Bootstrap to prevent MacOS[X] from mounting it. If MacOS is able to mount the bootstrap(8) partition it will make it unbootable by removing the attributes ybin(8) set to make the partition bootable by OpenFirmware. The bootstrap partition must not be mounted anywhere on your filesystem, ybin(8) and mkofboot(8) will refuse to operate on it if it is mounted. On IBM hardware the bootstrap(8) should be a type 0x41 PReP Boot partition.
This option defines the OpenFirmware device path to the bootstrap(8) partition. This is needed so the first stage ofboot.b loader can be configured properly. It should include the OpenFirmware path including the partition number (but not a filename). Example: if your bootstrap partition is /dev/hda2 the OF path will likely be hd:2. As of ybin(8) 0.18 you no longer are required to (and should not) specify this option. If left undefined ybin(8) will attempt to figure out the OpenFirmware path automatically using the ofpath(8) utility. You should only need to define this option if ofpath(8) fails.
Specifies the path to the yaboot(8) OpenFirmware executable file. This file is copied by ybin(8) to the bootstrap(8) partition. The default if this is not specified is /usr/local/lib/yaboot/yaboot or /usr/lib/yaboot/yaboot.
Specifies the path to an OpenFirmware CHRP script that ybin(8) will copy to the bootstrap(8) partition. Such a script contains Forth commands that can allow you to do interesting things such as creating a boot menu to choose between MacOS or GNU/Linux. Currently you must use a magicboot script do to a bug in OpenFirmware. Eventually a CHRP header could be added to the yaboot(8) executable so this can be optional. When this option is defined the magicboot script will be executed by OF automatically at boot (instead of the install file.) See man bootstrap(8) for more information on this. As of ybin 0.22 you should set this to /usr/local/lib/yaboot/ofboot which is a autoconfiguring first stage loader for yaboot. It is capable of presenting a dual boot menu for GNU/Linux, MacOS and MacOSX. If dual booting is not required or configured it will simply load yaboot directly. You must specify this for most PowerMacs or they will fail to boot. You cannot use magicboot scripts with IBM hardware.
Uses the specified image as the default boot image. If `default' is omitted, the image appearing first in the configuration file is used.
Defines the default OS for the first stage multiboot menu to load, by default this is linux, which really means yaboot. Valid values are: linux, bsd, macos, macosx, and darwin. This is only relevant if you have bsd=, macos=, macosx=, or darwin= options defined.
Specifies a file containing a message that is displayed before the boot prompt. You may specify either a plain pathname, in which case the default device and partition will be derived from the device= and partition= lines in the global section of yaboot.conf, or you can specify a full OpenFirmware device path, the file may be on any yaboot(8) supported filesystem. The message file must be plain ASCII text with UNIX newlines. Note: only the first 2000 bytes of this file will be read.
Protect booting by a password. The password is given in either cleartext or an md5 hash (of the same format as used in GNU/Linux passwd files)in the configuration file. Because of that, the configuration file should be only readable by the superuser and the password should differ if possible from other passwords on the system. See chmod(1) to set permissions on yaboot.conf(5). Passwords currently do not affect the multiboot menu entries ( macos=, macosx=, etc).
Sets a timeout (in tenths of a second) for keyboard input. If no key is pressed for the specified time, the first image is automatically booted.
Sets a timeout (in seconds) for an OS choice in the first stage ofboot loader. If no key is pressed for the specified time, the default OS defined by defaultos= (or GNU/Linux) is automatically booted. If this is left unset, the value of timeout= (converted to seconds) will be used.
Specifies that yaboot(8) should call OpenFirmware to execute the string given (a series of forth commands) before printing the boot prompt.
Specifies the foreground (text) color used by yaboot(8) and the multiboot menu. Available colors are: black, blue, light-blue, green, light-green, cyan, light-cyan, red, light-red, purple, light-purple, brown, light-gray, dark-gray, yellow, and white. The default is white.
Specifies the background color used by yaboot(8) and the mulitboot menu. Available colors are: black, blue, light-blue, green, light-green, cyan, light-cyan, red, light-red, purple, light-purple, brown, light-gray, dark-gray, yellow, and white. The default is black.
The OpenFirmware or Unix device path to a NetBSD or OpenBSD root partition, this partition must have the BSD kernel located at /bsd. You must also have the BSD bootloader ofwboot installed at /usr/local/lib/yaboot/ofwboot, ybin(8) will install this onto the bootstrap(8) partition. When you define this option you will be presented with a simple menu at bootup allowing you to hit L to boot GNU/Linux or B to boot BSD (along with other choices if configured). This will only work if you are using the new /usr/local/lib/yaboot/ofboot script. When this is set to a unix device node (ie /dev/hda11) then ybin will use the ofpath(8) utility to determine the OpenFirmware device path.
The OpenFirmware or Unix device path to a MacOS 8.* or 9.* boot partition. When you define this option you will be presented with a simple menu at bootup allowing you to hit L to boot GNU/Linux or M to boot MacOS (along with other choices if configured). This will only work if you are using the new /usr/local/lib/yaboot/ofboot script. When this is set to a unix device node (ie /dev/hda11) then ybin will use the ofpath(8) utility to determine the OpenFirmware device path.
The OpenFirmware or unix device path to a MacOS X boot partition. When you define this option you will be presented with a simple menu at bootup allowing you to hit L to boot GNU/Linux or X to boot MacOSX (along with other choices if configured). This will only work if you are using the new /usr/local/lib/yaboot/ofboot script. When this is set to a unix device node (ie /dev/hda11) then ybin will use the ofpath(8) utility to determine the OpenFirmware device path.
This option causes the menu entry for MacOSX to execute \System\Library\CoreServices\BootX from the macosx=device instead of the usual \\:tbxi. This is necessary if OSX is installed onto an HFS+ filesystem instead of UFS. When OSX is installed on an HFS+ filesystem MacOS will mount and debless the OSX partition. Add this option if the OSX menu entry breaks after booting MacOS. You should not use this option if OSX is installed on a UFS filesystem, for UFS installs you specify the OSX bootstrap partition which is protected against MacOS. This option requires macosx= to be set.
The OpenFirmware or unix device path to a Darwin boot partition. When you define this option you will be presented with a simple menu at bootup allowing you to hit L to boot GNU/Linux or D to boot Darwin (along with other choices if configured). This will only work if you are using the new /usr/local/lib/yaboot/ofboot script. When this is set to a unix device node (ie /dev/hda11) then ybin will use the ofpath(8) utility to determine the OpenFirmware device path.
This option adds an entry to the multiboot menu to boot from the CDROM drive.
This option adds an entry to the multiboot menu to boot from the network.
This option adds an entry to the multiboot menu to boot into an OpenFirmware prompt.
This option causes ybin to use the regular mount(8) utilities to access the filesystem on the bootstrap(8) partition instead of the userspace hfsutils(1). This is not recommended for HFS filesystems since it is not possible to set all the attributes required for automatic OpenFirmware booting. If you use this option you will have to modify OpenFirmware's boot-device variable to make your machine bootable (see man bootstrap(8)). Without this option you can normally reset OpenFirmware to its default configuration and your system will boot automatically into GNU/Linux. (See bootstrap(8) for details) This option is required for MSDOS filesystems.
Requires usemount this works exactly like usemount does except it does not mount the bootstrap(8) partition but rather installs the bootloader into the directory defined as the mountpoint. The pathname MUST be clean, ie no embedded spaces or metacharacters. The directory may not be more then one subdirectory deep from the root of the partition (not necessarily the unix /). You must not have a trailing / either. This option is NOT recommended since it has the same limitations as usemount, your system will not be bootable by OpenFirmware, it will only be manually bootable or bootable if you change the boot-device variable to the direct pathname to the bootloader (which ybin(8) will attempt to do). WARNING: This option is not secure if untrusted users can write to the value of mntpoint=, and the filesystem supports links.
Specifies what kind of filesystem is created on the bootstrap(8) partition by mkofboot(8). It must be either hfs or msdos or raw. For Apple PowerMacs HFS is the only workable option unless you have partitioned your disk with Intel partition tables. Ybin(8) also uses this option to determine how to access the partition properly. The raw type causes ybin(8) or mkofboot(8) to copy the bootloader (value of install=) to the bootstrap(8) partition without any filesystem. CAUTION: this will destroy any data or filesystem on the bootstrap(8) partition (value of boot=) if you specify something like boot=/dev/sda you will destroy the partition table and lose ALL data on the disk. The default if omitted, is hfs.
Specifies the four character HFS type code that is given to the boot loader (or magicboot script). The default is tbxi and should not be changed unless you really know what you are doing, OpenFirmware (on PowerMacs) looks for a file of this type to execute as a boot loader so if you change this your system will not boot automatically. This is only meant for users who must use a MacOS boot partition as the bootstrap partition, otherwise the conflict of two tbxi files could potentially cause MacOS to fail to boot. This code is only given to the file intended for OpenFirmware to boot. This option is ignored on non-HFS filesystems.
This prevents ybin(8) from “blessing” the root directory of the bootstrap(8) partition. Blessing the root directory is required for OpenFirmware to boot correctly. This should only be used when a MacOS boot partition is being used as the bootstrap(8) in which case blessing the root directory would make MacOS unbootable. If you use this option you must manually configure OpenFirmware to boot yaboot(8). (see bootstrap(8))
This causes ybin(8) to set the HFS invisible bit on all the boot loader files. OpenFirmware ignores this bit, but MacOS will not show invisible files in the Finder. This is useful if the bootstrap(8) partition is MacOS mountable and you want to prevent annoying MacOS lusers from screwing up your GNU/Linux boot loader ;-). This option is ignored for non-HFS filesystems.
This causes ybin(8) to set the HFS/MSDOS read-only bit on all the boot loader files. MacOS will not allow a read-only file to be modified or deleted (but does not prevent anyone from removing this bit) This is only useful if the bootstrap(8) partition is MacOS mountable and you want to discourage modification/deletion of the boot loader.
This option prevents ybin(8) from setting the OpenFirmware boot-device variable with nvsetenv(8).
In addition to these global options, per-image options append, device, image, initrd-prompt, initrd-size, initrd, partition, pause-after, pause-message, ramdisk, read-only, read-write, root and restricted can be specified in the global section. They are used as defaults if they aren't specified in the configuration sections of the respective kernel images and will be used also for the arbitrary images specified on the input line and not mentioned in the configuration file (unless overridden by input line options).


A per-image section starts with either a line

(for booting from files) From the image line on until next image line are variable assignments and flags for this image's section. The following options and flags are recognized:
The bootloader uses the main file name (without its path) of each image specification to identify that image. A different name can be used by setting the variable `label'.
A second name for the same entry can be used by specifying an alias.
Specifies the default partition number (a digit, hda1 is part_no 1) to be used if some filename does not specify a partition number explicitly. The kernel images should be located on the root filesystem, thus partition should usually be set to the root partition number. For example if the root partition is /dev/hda3 (the third partition), then partition should be set to partition=3.
Specifies the default device name to be used if some filename does not specify a device name explicitly. This defaults to the device yaboot has been booted from if you don't specify device in either the global section or per-image section of the config file.
Appends the options specified to the parameter line passed to the kernel. This is typically used to specify parameters of hardware that can't be entirely auto-detected or for which probing may be dangerous. Example:

append = "video=ofonly"
Like `append', but removes all other options (e.g. setting of the root device). Because vital options can be removed unintentionally with `literal', this option cannot be set in the global options section.
This specifies the size of the optional RAM disk. A value of zero indicates that no RAM disk should be created. If this variable is omitted, the RAM disk size configured into the boot image is used.
This specifies that the root file system should be mounted read-only. Typically, the system startup procedure re-mounts the root file system read-write later (e.g. after fsck'ing it).
This specifies that the root file system should be mounted read-write.
This specifies the device that should be mounted as root.
Specifies the file that will be loaded at boot time as the initial RAM disk. Example:

yaboot will not decompress the initial ramdisk, the Linux kernel will do that. If the initial ramdisk does not fit on one media (usually floppy), you can split it into several pieces and separate the filenames in the list by | characters. In this case, you have to provide a non-zero initrd-size and, if the images reside on different medias, initrd-prompt as well. Example (on the first floppy is initrd1.img, on the second initrd2.img always in the root directory and the sum of both image sizes is 1700000 bytes):

When more than one initial ramdisk part is specified in the initrd setting, this option is required to be the sum of sizes of all the images mentioned on that line, in bytes. It is required so that yaboot can reserve space for the image, even though size of some parts has not been determined yet.
If more than one initial ramdisk part is specified, wait for user pressing a key between loading the different images, so that the user can exchange media. This flag is needed if some initrd parts reside on the same device, but different removable media. On the other side, if you e.g. load one part from a floppy and the second part from a hard disk, such option is not needed (the question is who'd write something like that into yaboot.conf).
If this flag is specified, yaboot will stop after loading the kernel (and initial ramdisks if specified) and ask the user to press a key before continuing.
If pause-after is specified, this variable specifies the string to print to the user when asking him to press a key. The default is:

Press ENTER to continue.
Enables booting the image by hitting a single key when the cursor is at the first character in the input line, without the need to press <ENTER> afterwards. single-key requires that either the image's label or its alias (or both) is a single character. If you need to specify parameters for such an image, or if you want to boot some other image which happens to start with the same letter, then you need to start the input line with at least one space which will be removed before processing but will disable this single-key feature.
Restricted limits the ability to customize command line arguments. restricted has no effect if password= is not specified. A password is only required to boot the image specified in /etc/yaboot.conf if parameters are specified on the command line or if the user enters an image that is not specified in the configuration file at all (arbitrary file load). For an image not including the restricted keyword (unless restricted is in the global section), the password will be required. If restricted is in the global section, all boot labels act as above (duh:).


Here is an example yaboot.conf file:
image=/boot/vmlinux label=Linux read-only restricted
image=/boot/vmlinux.old label=linux.old read-only
macos=hd:9 macosx=/dev/hda10


The format defined in this man page will not work with versions of yaboot(8) older then 0.6. The color options only work with yaboot 1.0 and later.


Some yaboot options may not be implemented fully.


This man page was derived from silo.conf(5) written by Jakub Jelinek and the SparcLinux team, and modified for yaboot(8)/ybin(8) by Ethan Benson.
yaboot(8) was written by Benjamin Herrenschmidt <>.
ybin(8) was written by Ethan Benson <>.


bootstrap(8), chmod(1), hfsutils(1), mkofboot(8), mount(8), nvsetenv(8), ofpath(8), yaboot(8), ybin(8).
28 October 2001 GNU/Linux PowerPC