bless(8)

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. Create a BootX 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 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 provided, 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

--setBoot

Set the system to boot off the specified partition. 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. This is not supported on Apple Silicon based systems.

--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-partitioned 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 systems, and in general should be avoided. Instead, use nvram(8) to set "boot-args" , which will work with both Open Firmware- and EFI-based systems.

--personalize

Attempts to do a personalization operation on the target, which validates the SecureBoot bundle and ensures that the relevant boot files are signed and valid for this particular machine. This may require network access, in order to check the signatures.

Only one of the following snapshot options can be activated at the same time:

--create-snapshot

Attempts to create an APFS root snapshot of the target APFS system volume and set it as root snapshot of the system volume. The target system will boot from this snapshot on its next boot.

--snapshot

Set specific snapshot (uuid) as root snapshot of the system volume. The target system will boot from this snapshot on its next boot.

--snapshotname

Set specific snapshot (name) as root snapshot of the system volume. The target system will boot from this snapshot on its next boot.

--last-sealed-snapshot

Reverts back to using the previously signed APFS root snapshot reenabling Authenticated Root Volume.
The target system will boot from this sealed snapshot on its next boot.

--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 device, 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.

--personalize

Same as for Folder Mode.

--create-snapshot

Same as for Folder Mode.

--snapshot

Same as for Folder Mode.

--snapshotname

Same as for Folder Mode.

--last-sealed-snapshot

Same as for Folder Mode.

--bootefi

This enables copying required boot objects when --create-snapshot or --last-sealed-snapshot is given.

--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 device. 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 partition, 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 Protocol. 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 available server. Examples of this notation would be "bsdp://255.255.255.255" and "bsdp://[email protected]".

--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 volume mounted at directory . If directory is not specified, print information for the currently selected boot device (which may not necessarily be‘ /’ ). This is not supported on Apple Silicon based systems.

--getBoot

Print out the logical boot device, 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.

FOLDER MODE - Available only for external/removable devices

Folder Mode has the following options:

--folder directory

Set this directory to be the Mac OS X/Darwin blessed directory, containing a booter for EFI-based systems.

--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.

--personalize

Attempts to do a personalization operation on the target, which validates the SecureBoot bundle and ensures that the relevant boot files are signed and valid for this particular machine. This may require network access, in order to check the signatures.

--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 device, in conjunction with --setBoot. The volume must already be properly blessed.

--nextonly

Only change the boot device selection for the next boot.

--create-snapshot

Attempts to create an APFS root snapshot of the target APFS system volume and set it as root snapshot of the system volume. The target system will boot from this snapshot on its next boot.

--snapshot

Set specific snapshot (uuid) as root snapshot of the system volume. The target system will boot from this snapshot on its next boot.

--snapshotname

Set specific snapshot (name) as root snapshot of the system volume. The target system will boot from this snapshot on its next boot.

--last-sealed-snapshot

Reverts back to using the previously signed APFS root snapshot reenabling Authenticated Root Volume. The target system will boot from this sealed snapshot on its next boot.

--user

Collect a local owner username to authorize boot policy modification.

--stdinpass

Collect a local owner password from stdin without prompting.

--passpromt

Explicitly ask to be prompted for the password.

--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 device. No volumes should be mounted from device , and the filesystem should already be properly blessed.

--setBoot

Set the system to boot off the specified volume, as with Mount and Device mode Modes. for the startup file type.

--nextonly

Same as for Mount Mode.

--user

Collect a local owner username to authorize boot policy modification.

--stdinpass

Collect a local owner password from stdin without prompting.

--passpromt

Explicitly ask to be prompted for the password.

--quiet

Do not print any output

--verbose

Print verbose output

INFO MODE

Info Mode has the following options:

--info [directory]

(Available only for external/removable devices) Print out the blessed system folder for the volume mounted at directory . If directory is not specified, print information for the currently selected boot device (which may not necessarily be‘ /’ ).

--getBoot

Print out the logical boot device, 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.

--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.

--user

Collect a local owner username to authorize boot policy modification.

--stdinpass

Collect a local owner password from stdin without prompting.

--passpromt

Explicitly ask to be prompted for the password.

--quiet

Do not print any output

--verbose

Print verbose output

--version

Print bless version and exit immediately

FOLDER MODE

To bless a volume with only Mac OS X or Darwin, and create the BootX and boot.efi files as needed:

MOUNT MODE

To set a volume containing either Mac OS 9 and Mac OS X to be the active volume:

NETBOOT MODE

To set the system to NetBoot and broadcast for an available server:

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: