.\" Automatically generated from mdocxml
.Dd December 14, 2015
.Dt "com.apple.Boot.plist" 5
.Os "Darwin" ""
.Sh NAME
.Nm com.apple.Boot.plist
.Nd Configuration plist for \&OS \&X booter
.Sh DESCRIPTION
The \&OS \&X booter \&(
.Pa boot.efi
\&on EFI-based Macintosh systems) \&is responsible for loading the initial parts \&of the operating system into memory and executing them. Its default behavior \&is \&to start \&up \&OS \&X \&in graphical mode. However, certain behavior can \&be configured using the 
.Pa com.apple.Boot.plist
file, \&as well \&as NVRAM variables, EFI boot options, and keyboard "snag keys". 
.Pp
The 
.Pa com.apple.Boot.plist
\&is \&a standard 
.Xr plist 5  
format Core Foundation property list stored \&in XML format. Keys are generally strings like 
.Nm Kernel Flags,
with either string \&or integer values. The following key-values are currently supported: 
.Pp
.Bl -tag -width XXXXX
.It  Nm Kernel Flags
[string] This option specifies arguments \&to \&be passed directly \&to the kernel \&to change its behavior (although some kernel options are parsed \&by the booter \&as well for correctness). Common options include "debug=0x144" \&to enable kernel debugging, "-v" \&to enable verbose boot, "-s" \&to boot \&to single user mode, "cpus=1" \&to simulate \&a single core system, and "maxmem=1024" \&to cap available memory \&to 1024 \&MB RAM. All desired options should \&be space-separated within the <string> tag. The default value \&is the empty string.
.It  Nm Kernel Cache
[string] This option specifies the prelinked kernel file \&to \&be loaded, which contains both the kernel and kernel extensions, linked \&at their final load addresses. The path uses backslash \&("\e \&") path delimeters. The default value \&is calculated programmatically using 
.Pa System\e Library\e PrelinkedKernels\e prelinkedkernel.
.It  Nm Root UUID
[string] This option \&is rarely used and specifies \&to the kernel what block device should \&be probed \&as the root filesystem ("/"), and \&is most commonly overriden \&by the \&OS installation software when installing onto AppleRAID volumes. \&It can \&be either \&a filesystem volume UUID, \&as represented \&by 
.Nm diskutil info,
\&or \&a GPT partition UUID. The default \&is generated programmatically based \&on which filesystem the booter itself was loaded from.
.El
.Pp
Since the 
.Pa com.apple.Boot.plist
file exists \&on the root filesystem, \&it \&is tied \&to that  \&OS volume, and \&is \&no longer honored \&if Startup Disk \&or 
.Xr bless 8  
\&is used \&to change the boot preference \&to another volume. 
.Pp
The 
.Nm Kernel Flags
options can also \&be specified via 
.Pa --option\&to 
.Xr bless 8  ,
which encodes the string \&in the EFI boot options along with the \&OS boot volume preference. The space-separated strings are merged with kernel flags specified \&in the 
.Pa com.apple.Boot.plist
and NVRAM. 
.Pp
\&At boot time, the booter checks \&to see \&if certain keys are being pressed, and alters behavior accordingly. This \&is \&in addition \&to similar functionality that the firmware itself may implement before starting the booter. Since pressing keys requires physical interaction, they take precendence over preferences set through other means, including the 
.Pa com.apple.Boot.plist
file and NVRAM. The following key combinations are currently supported: 
.Pp
.Bl -tag -width XXXXX
.It  Nm Shift
Boot \&in Safe Mode. Effectively the same \&as passing "-x" \&in 
.Nm Kernel Flags,
and causes most caches \&to \&be ignored \&by the booter.
.It  Nm Command-S
Boot \&in Single User Mode. Effectively the same \&as passing "-s" \&in 
.Nm Kernel Flags,
and causes the system \&to boot \&to \&an interactive shell with \&no system services started.
.It  Nm Command-V
Boot \&in Verbose Mode. Effectively the same \&as passing "-v" \&in 
.Nm Kernel Flags,
and causes the system \&to boot \&to verbose text logging before starting the graphical user interface.
.It  Nm Command-R
Boot \&in Recovery Mode.  This causes the system \&to boot into special Recovery System image, which can \&be used \&to restore the system from Time Machine Backup, re-install \&OS \&X, \&or use Disk Utility \&to repair \&or erase disks.
.El
.Pp
.Sh ENVIRONMENT
The \&OS \&X booter can also \&be controlled \&by NVRAM variables, which are analogous \&to environment variables. NVRAM variables are key-value pairs. The "boot-args" NVRAM variable can \&be used \&to provide additional arguments \&to the kernel, and will \&be merged with 
.Nm Kernel Flags
\&in the 
.Pa com.apple.Boot.plist
file and EFI boot options set with 
.Xr bless 8  .
.Pp
Since NVRAM variables are system-wide, they are consulted regardless \&of what \&OS volume \&is set \&as the boot preference. NVRAM variables are persistent even when the boot preference \&is changed \&by Startup Disk \&or 
.Xr bless 8  .
.Pp
.Sh FILES
.Bl -tag -width indent
.It Pa /Library/Preferences/SystemConfiguration/com.apple.Boot.plist
Location \&of the 
.Pa com.apple.Boot.plist
file.
.El
.Sh SEE ALSO
.Xr nvram 8 ,  
.Xr bless 8 ,  
.Xr kextcache 8