42cd37dfbd
Add a man page for gptboot.efi. Describe when and how to use this as it differs from the BIOS cases. Include cross reference for the preferred method described in efibootmgr(8) as well as cross links in both gptboot(8) and gptboot.efi(8) to the other. This man page was heavily copied from the gptboot.8 man page by Warren Block. They are different enough to need separate man pages for clarity, but there's enough similarity that I worry about the duplication. In the really long term, gptboot(8) will disappear, so having the same info here will help when that day comes. In the short to medium term, the information is likely to not change in gptboot(8) and any changes to gptboot.efi(8) will be easier to make in a separate copy. loader.efi(8) needs a complete rewrite from scratch, otherwise I'd have referenced gptboot.efi(8) from there. Suggetions from: cress@, mhorne@ Reviewed by: rpokala@ Differential Revision: https://reviews.freebsd.org/D29591
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7.5 KiB
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283 lines
7.5 KiB
Groff
.\" Copyright (c) 2013 Warren Block All rights reserved.
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.\" Copyright (c) 2021 Warner Losh
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 6, 2021
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.Dt GPTBOOT.EFI 8
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.Os
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.Sh NAME
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.Nm gptboot.efi
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.Nd GPT bootcode for UFS on UEFI computers
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.Sh DESCRIPTION
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.Nm
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is used on UEFI computers to boot from a UFS partition on a
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GPT-partitioned disk.
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.Nm
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is installed in the EFI System Partition (ESP).
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For BIOS-based computers,
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see
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.Xr gptboot 8
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for details.
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While conceptually similar, the details differ.
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.Nm
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works only with UFS root file systems.
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Users with ZFS partitions should use
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.Xr loader.efi 8
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with
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.Xr bectl 8
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to control what dataset is used for root.
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.Pp
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What UEFI computers boot is usually controlled via the mechanisms explained in
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.Xr efibootmgr 8
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using
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.Xr loader.efi 8
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or
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.Xr boot1.efi 8 .
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However, some setups cannot use those mechanisms.
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When the users cannot rely on host-supplied UEFI variables
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or they want the contents of the media alone to decide root,
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.Nm
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accomplishes these goals.
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.Pp
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When it starts,
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.Nm
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first reads the GPT and determines which drive and partition to
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boot from, as described under
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.Sx BOOTING ,
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below.
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If it does not find an eligible partition, it returns to the UEFI
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firmware.
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The firmware will then try the next bootable item in the UEFI Boot Manager's
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list, if any, usually a different disk.
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.Sh IMPLEMENTATION NOTES
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The GPT standard allows a variable number of partitions, but
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.Nm
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only boots from tables with 128 partitions or less.
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.Sh PARTITION ATTRIBUTES
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.Nm
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checks and manages several attributes of GPT UFS partitions.
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These flags are
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.Fx
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specific and non-standard.
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.Bl -tag -width ".Cm bootfailed"
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.It Cm bootme
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Attempt to boot from this partition.
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If more than one partition has the
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.Cm bootme
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attribute set,
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.Nm
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will attempt to boot each one until successful.
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.It Cm bootonce
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Attempt to boot from this partition only one time.
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Setting this attribute with
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.Xr gpart 8
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automatically also sets the
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.Cm bootme
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attribute.
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Multiple partitions may have the
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.Cm bootonce
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and
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.Cm bootme
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attributes set.
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.It Cm bootfailed
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The
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.Cm bootfailed
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attribute marks partitions that had the
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.Cm bootonce
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attribute set, but failed to boot.
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This attribute is managed by the system.
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See
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.Sx "BOOTING"
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and
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.Sx "POST-BOOT ACTIONS"
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below for details.
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.El
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.Sh USAGE
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For normal usage, the user does not have to set or manage any of the
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partition attributes.
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.Nm
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will boot from the first UFS partition found on the device.
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.Pp
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The
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.Cm bootonce
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attribute can be used for testing an upgraded operating system on
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an already-working computer.
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The existing system partition is left untouched, and the new version
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of the operating system to be tested is installed on another partition.
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The
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.Cm bootonce
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attribute is set on that new test partition.
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The next boot is attempted from the test partition.
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Success or failure will be shown in the system log files.
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After a successful boot of the test partition, a user script can check
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the logs and change the
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.Cm bootme
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attributes so the test partition becomes the new system partition.
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Because the
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.Cm bootonce
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attribute is cleared after an attempted boot, a failed boot will not
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leave the system attempting to boot from a partition that will never
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succeed.
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Instead, the system will boot from the older, known-working operating
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system that has not been modified.
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If the
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.Cm bootme
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attribute is set on any partitions, booting will be attempted from them
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first.
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If no partitions with
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.Cm bootme
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attributes are found, booting will be attempted from the first UFS
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partition found.
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.Sh BOOTING
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.Nm
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first reads the partition table.
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All
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.Cm freebsd-ufs
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partitions with only the
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.Cm bootonce
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attribute set, indicating a failed boot, are set to
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.Cm bootfailed .
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.Nm
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then scans through all of the
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.Cm freebsd-ufs
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partitions.
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Boot behavior depends on the combination of
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.Cm bootme
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and
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.Cm bootonce
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attributes set on those partitions.
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.Bl -tag -width ".Cm bootonce + .Cm bootme"
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.It Cm bootonce + Cm bootme
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Highest priority: booting is attempted from each of the
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.Cm freebsd-ufs
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partitions with both of these attributes.
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On each partition, the
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.Cm bootme
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attribute is removed and the boot attempted.
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.It Cm bootme
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Middle priority: booting is attempted from each of the
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.Cm freebsd-ufs
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partitions with the
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.Cm bootme
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attribute.
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.El
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.Pp
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If neither
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.Cm bootonce
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nor
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.Cm bootme
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attributes are found on any partitions, booting is attempted from the
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first
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.Cm freebsd-ufs
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partition on the disk.
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.Sh POST-BOOT ACTIONS
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The startup script
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.Pa /etc/rc.d/gptboot
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checks the attributes of
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.Cm freebsd-ufs
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partitions on all GPT disks.
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Partitions with the
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.Cm bootfailed
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attribute generate a
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.Dq boot from X failed
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system log message.
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Partitions with only the
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.Cm bootonce
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attribute, indicating a partition that successfully booted, generate a
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.Dq boot from X succeeded
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system log message.
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The
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.Cm bootfailed
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attributes are cleared from all the partitions.
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The
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.Cm bootonce
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attribute is cleared from the partition that successfully booted.
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There is normally only one of these.
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.Sh FILES
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.Bl -tag -width /boot/gptboot.efi -compact
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.It Pa /boot/gptboot.efi
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bootcode binary
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.It Pa /boot/efi/efi/boot/bootx64.efi
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Default boot loader for amd64 systems.
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.It Pa /boot/efi/efi/boot/bootaa64.efi
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Default boot loader for arm64 systems.
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.It Pa /boot/efi/efi/boot/bootarm.efi
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Default boot loader for arm systems.
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.It Pa /boot/efi/efi/boot/bootriscv64.efi
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Default boot loader for riscv systems.
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.El
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.Sh EXAMPLES
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.Nm
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is installed in the ESP with
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.Xr cp 1 .
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.Pp
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Install
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.Nm
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into the ESP for the system.
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This assumes the ESP is mounted in the standard
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.Pa /boot/efi
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directory.
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For amd64, use the following
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.Bd -literal -offset indent -compact
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cp /boot/gptboot.efi /boot/efi/efi/boot/bootx64.efi
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.Ed
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For other systems, use the file listed in the
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.Sx FILES
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section.
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.Pp
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Set the
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.Cm bootme
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attribute for partition 2:
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.Bd -literal -offset indent
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gpart set -a bootme -i 2 ada0
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.Ed
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.Pp
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Set the
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.Cm bootonce
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attribute for partition 2, automatically also setting the
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.Cm bootme
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attribute:
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.Bd -literal -offset indent
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gpart set -a bootonce -i 2 ada0
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.Ed
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.Sh SEE ALSO
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.Xr rc.conf 5 ,
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.Xr boot 8 ,
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.Xr efibootmgr 8 ,
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.Xr gpart 8 ,
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.Xr gptboot 8 ,
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.Xr loader.efi 8
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.Sh HISTORY
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.Nm
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appeared in
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.Fx 13.0
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.Sh AUTHORS
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This manual page written by
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.An Warner Losh Aq imp@FreeBSD.org .
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It is based heavily on the
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.Xr gptboot 8
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man page by
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.An Warren Block Aq wblock@FreeBSD.org .
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