bless(8) BSD System Manager's Manual bless(8)
NAME
bless -- set volume bootability and startup disk options
SYNOPSIS
bless --help
bless --folder directory [--file file] [--bootinfo [file]]
[--bootefi [file]] [--label name | --labelfile file] [--setBoot]
[--openfolder directory] [--nextonly] [--shortform] [--legacy]
[--legacydrivehint device] [--options string] [--quiet | --verbose]
bless --mount directory [--file file] [--setBoot] [--nextonly]
[--shortform] [--legacy] [--legacydrivehint device]
[--options string] [--quiet | --verbose]
bless --device device [--label name | --labelfile file]
[--startupfile file] [--setBoot] [--nextonly] [--shortform]
[--legacy] [--legacydrivehint device] [--options string]
[--quiet | --verbose]
bless --netboot --server url [--nextonly] [--options string]
[--quiet | --verbose]
bless --info [directory] [--getBoot] [--plist] [--quiet | --verbose]
[--version]
bless --unbless directory
DESCRIPTION
bless is used to modify the volume bootability characteristics of
filesystems, as well as select the active boot volume. bless has 6 modes
of execution: Folder Mode, Mount Mode, Device Mode, NetBoot Mode, Info
Mode, and Unbless Mode.
Folder Mode allows you to select a directory on a mounted volume to act
as the ``blessed'' directory, which causes the system firmware to look in
that directory for boot code. EFI-based systems also support a
``blessed'' system file, which is the primary mechanism of specifying the
booter for a volume for those systems. In Folder Mode, if you are operat-
ing on an HFS+ volume, the HFS+ Volume Header is updated to reflect the
files/directories given, which persists even if the volume is moved to
another system or NVRAM is cleared.
Mount Mode does not make permanent modifications to the filesystem, but
rather set the system firmware to boot from the specified volume, assum-
ing it has been properly blessed. This is a subset of the functionality
of Folder Mode with the --setBoot option, but is convenient when you
don't want to change or interrogate the filesystem for its blessed sta-
tus.
Device Mode is similar to Mount Mode, but allows selection of unmounted
filesystems, for instance while in single user mode. It can also perform
certain offline modifications to the filesystem, but is not generally
recommended.
NetBoot Mode sets the system firmware to boot from the network, using a
URL syntax to specify the protocol and server. bless only sets the local
system to go into NetBoot mode, and does not communicate to the server
what image should be used, if there are multiple images. Some other mech-
anism, such as using Startup Disk, should be used to select that.
Info Mode will print out the currently-blessed directory of a volume, or
if no mountpoint is specified, the active boot volume that the firmware
is set to boot from.
Unbless Mode complements Folder Mode, and clears the persistent blessed
folder and file information on HFS+ volumes.
Additionally, --help can be used to display the command-line usage sum-
mary.
FILE/FOLDER MODE
Folder Mode has the following options:
--folder directory Set this directory to be the Mac OS X/Darwin
blessed directory, containing a BootX secondary
loader for New World machines.
--file file Set this file to be the Mac OS X/Darwin blessed
boot file, containing a booter for EFI-based
systems. If this option is not provided, a
default boot file is used based on the blessed
directory.
--bootinfo [file] Create a BootX file in the Mac OS X/Darwin sys-
tem folder using file as a source. If file is
not provided, a default is used (see FILES),
using a path relative to the mountpoint you are
blessing. This attempts to ensure that a BootX
is used that is compatible with the OS on the
target volume.
--bootefi [file] Create a boot.efi file in the Mac OS X/Darwin
system folder using file as a source. If file is
not provided, a default is used (see FILES),
using a path relative to the mountpoint you are
blessing. This attempts to ensure that a
boot.efi is used that is compatible with the OS
on the target volume. If --file is also pro-
vided, the new file will be created at that path
instead.
--label name Render a text label used in the firmware-based
OS picker
--labelfile file Use a pre-rendered label used for the firmware-
based OS picker
--openfolder directory Specify a folder to be opened in the Finder when
the volume is mounted by the system.
--setBoot Set the system to boot off the specified parti-
tion. This is implemented in a platform-specific
manner. On Open Firmware-based systems, the
boot-device variable is modified. On EFI-based
systems, the efi-boot-device variable is
changed.
--nextonly Only change the boot device selection for the
next boot. This is only supported on EFI-based
systems.
--shortform Use an abbreviated device path form. This option
can allow for booting from new devices, at the
expense of boot time performance. This is only
supported on EFI-based systems.
--legacy If --setBoot is given, set the firmware to boot
a legacy BIOS-based operating system from the
specified disk. The active flag of an MBR-parti-
tioned disk is not modified, which can be done
with fdisk(8) . This is only supported on EFI-
based systems.
--legacydrivehint device
Instruct the firmware to treat the specified
whole disk as the primary, master IDE drive.
This is only supported on EFI-based systems.
--options Set load options associated with the new boot
option. This is only supported on EFI-based sys-
tems, and in general should be avoided. Instead,
use nvram(8) to set "boot-args" , which will
work with both Open Firmware- and EFI-based sys-
tems.
--quiet Do not print any output
--verbose Print verbose output
MOUNT MODE
Mount Mode has the following options:
--mount directory Use the volume mounted at directory to change
the active boot volume, in conjunction with
--setBoot . The volume must already be properly
blessed.
--file file Instead of allowing the firmware to discover the
booter based on the blessed directory or file,
pass an explicit path to the firmware to boot
from. This can be used to run EFI applications
or EFI booters for alternate OSes, but should
not be normally used. This is only supported on
EFI-based systems.
--setBoot Same as for Folder Mode.
--nextonly Same as for Folder Mode.
--shortform Same as for Folder Mode.
--legacy Same as for Folder Mode.
--legacydrivehint device
Same as for Folder Mode.
--options Same as for Folder Mode.
--quiet Do not print any output
--verbose Print verbose output
DEVICE MODE
Device Mode has the following options:
--device device Use the block device device to change the active
boot volume. No volumes should be mounted from
device , and the filesystem should already be
properly blessed.
--label name Set the firmware-based OS picker label for the
unmounted filesystem, using name , which should
be in UTF-8 encoding.
--labelfile file Use a pre-rendered label used with the firmware-
based OS picker.
--setBoot Set the system to boot off the specified parti-
tion, as with Folder and Mount Modes.
--startupfile file Add the file as the HFS+ StartupFile, and update
other information on disk as appropriate for the
startup file type.
--nextonly Same as for Folder Mode.
--shortform Same as for Folder Mode.
--options Same as for Folder Mode.
--legacy Same as for Folder Mode.
--legacydrivehint device
Same as for Folder Mode.
--quiet Do not print any output
--verbose Print verbose output
NETBOOT MODE
NetBoot Mode has the following options:
--netboot Instead of setting the active boot selection to
a disk-based volume, set the system to NetBoot.
--server protocol://[interface@]server
A URL specification of how to boot the system.
Currently, the only protocol supported is BSDP
("bsdp"), Apple's Boot Service Discovery Proto-
col. The interface is optional, and the server
is the IPv4 address of the server in dotted-quad
notation. If there is not a specific server
you'd like to use, pass "255.255.255.255" to
have the firmware broadcast for the first avail-
able server. Examples of this notation would be
"bsdp://255.255.255.255" and
"bsdp://en1@17.203.12.203".
--nextonly Same as for Folder Mode.
--options Same as for Folder Mode.
--quiet Do not print any output
--verbose Print verbose output
INFO MODE
Info Mode has the following options:
--info [directory] Print out the blessed system folder for the vol-
ume mounted at directory . If directory is not
specified, print information for the currently
selected boot volume (which may not necessarily
be `/' .
--getBoot Print out the logical boot volume, based on what
is currently selected. This option will take
into account the fact that the firmware may be
pointing to an auxiliary booter partition, and
will print out the corresponding root partition
for those cases. If the system is configured to
NetBoot, a URL matching the format of the
--server specification for NetBoot mode will be
printed.
--plist Output all information in Property List (.plist)
format, suitable for parsing by CoreFoundation.
This is most useful when bless is executed from
another program and its standard output must be
parsed.
--quiet Do not print any output
--verbose Print verbose output
--version Print bless version and exit immediately
UNBLESS MODE
Unbless Mode has the following options:
--unbless directory Use the HFS+ volume mounted at directory and
unset any persistent blessed files/directories
in the HFS+ Volume Header.
FILES
/usr/standalone/ppc/bootx.bootinfo Secondary loader with XML headers,
used with the --bootinfo flag. Used
for booting New World PPC-based Mac-
intoshes. If the argument to
--bootinfo is ommitted, this file
will be used as the default input.
/usr/standalone/i386/boot.efi Booter for EFI-based systems, used
with the --bootefi flag. If the argu-
ment to --bootefi is ommitted, this
file will be used as the default
input.
/System/Library/CoreServices Typical blessed folder for Mac OS X
and Darwin
EXAMPLES
FOLDER MODE
To bless a volume with only Mac OS X or Darwin, and create the BootX and
boot.efi files as needed:
bless --folder "/Volumes/Mac OS X/System/Library/CoreServices"
--bootinfo --bootefi
MOUNT MODE
To set a volume containing either Mac OS 9 and Mac OS X to be the active
volume:
bless --mount "/Volumes/Mac OS" --setBoot
NETBOOT MODE
To set the system to NetBoot and broadcast for an available server:
bless --netboot --server bsdp://255.255.255.255
INFO MODE
To gather information about the currently selected volume (as determined
by the firmware), suitable for piping to a program capable of parsing
Property Lists:
bless --info --plist
SEE ALSO
mount(8), newfs(8), nvram(8)
Mac OS X May 24, 2013 Mac OS X
Mac OS X 10.9 - Generated Thu Oct 17 06:35:22 CDT 2013