.Dd October 5, 2015
.Dt KERNEL 7
.Os
.Sh NAME
.Nm kernel
.Nd operating system kernel
.Sh SYNOPSIS
.Pa /boot/sortix.bin
.Op Fl \-disable-em
.Op Fl \-enable-em
.Op Fl \-disable-network-drivers
.Op Fl \-enable-network-drivers
.Op Fl \-no-random-seed
.Op Fl \-
.Op Ar init ...
.Sh DESCRIPTION
.Pa /boot/sortix.bin
is the operating system
.Nm kernel .
It initializes and manages the hardware to provide a multitasking computing
environment.
The kernel is a
.Xr multiboot 7
compatible executable loaded by the bootloader along with a companion
.Xr initrd 7
that contains a userland.
.Pp
The kernel extracts the initrd into the initial kernel memory root filesystem.
The specified
.Ar init
program is invoked with the given arguments, defaulting to the
.Xr init 8
at
.Pa /sbin/init
if
.Ar init
is not specified.
If the
.Nm init
is to receive any argument starting with a dash, first pass the
.Fl \-
delimiter to stop kernel option parsing.
The computer is powered off if the
.Nm init
process exits 0, rebooted if it exits 1,
halted with an complaint about an
.Nm init
fatality if it exits 2, and halted with a complaint about an unexpected exit code
otherwise.
.Pp
The options are as follows:
.Bl -tag -width "12345678"
.It Fl \-disable-em
Don't initialize the
.Xr em 4
driver.
.It Fl \-disable-network-drivers
Don't initialize any network drivers.
This option ensures the booted system is not networked.
.It Fl \-enable-em
Do initialize the
.Xr em 4
driver.
.It Fl \-enable-network-drivers
Do initialize network drivers.
This is the default behavior.
.It Fl \-no-random-seed
Don't warn if no random seed file was loaded by the bootloader (usually from
.Pa /boot/random.seed ) .
This option is useful for live environments where this situation is unavoidable.
.El
.Pp
The kernel accepts multiboot modules from the bootloader, which are processed
in order.
The
.Xr initrd 7
must be passed through this mechanism.
.Pp
The format of each multiboot module is automatically detected by default:
.Pp
.Bl -bullet -compact
.It
Initialization ramdisks produced by
.Xr mkinitrd 8
are extracted in the root directory.
.It
.Xr tar 7
archives in the ustar format are extracted into the root directory.
The bootloader must already have decompressed the archive.
If the archive contains the
.Pa tix/tixinfo
file, it is instead installed into the root directory as a
.Xr tix 7
binary package.
.El
.Pp
Each multiboot module has its own command line where the options are as follows:
.Bl -tag -width "12345678"
.It Fl \-append-to Ns "=" Ns Ar file
Append the contents of the module to the specifed
.Ar file ,
creating it with mode 644 if it doesn't exist.
Non-existent parent directories are created with mode 755 as needed.
.It Fl \-create-to Ns "=" Ns Ar file
Create the specified
.Ar file
with mode 644 with contents of the module, but only if it doesn't already exist.
No action is taken if the file already existed.
Non-existent parent directories are created with mode 755 as needed.
.It Fl \-random-seed
The module contains random data used to seed the kernel entropy gathering.
This file is supposed to contain 256 bytes of secret randomness that hasn't been
used before.
Recycling the random seed is dangerous and insecure.
Omitting the random seed will cause the kernel entropy to be insecurely seeded
with the current time and other readily available information.
The bootloader normally loads the random seed from
.Pa /boot/random.seed .
.It Fl \-tar
The module is a
.Xr tar 7
archive that is extracted into the root directory.
.It Fl \-tix
The module is a
.Xr tix 7
binary package that is installed into the root directory.
.It Fl \-to Ns "=" Ns Ar file
Write the contents of the module to the specifed
.Ar file ,
creating it with mode 644 if it doesn't exist, and truncating it if it does exist.
Non-existent parent directories are created with mode 755 as needed.
.El
.Sh SEE ALSO
.Xr initrd 7 ,
.Xr init 8