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3809fd35a5
We have previously added logic to allow a "fallback" option to be
specified in the extlinux configuration. Provide a command that allows
us to set this as the preferred default option when booting.
Combined with the bootcount functionality, this allows the "altbootcmd"
to provide a means of falling back to a previously known good state
after a failed update. For example, if "bootcmd" is set to:
bootflow scan -lb
We would set "altbootcmd" to:
bootmeth set extlinux fallback 1; bootflow scan -lb
Causing the boot process to boot from the fallback option.
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Martyn Welch <martyn.welch@collabora.com>
151 lines
4.8 KiB
ReStructuredText
151 lines
4.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+:
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.. index::
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single: bootmeth (command)
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bootmeth command
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================
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Synopsis
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--------
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::
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bootmeth list [-a] - list selected bootmeths (-a for all)
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bootmeth order "[<bm> ...]" - select the order of bootmeths
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bootmeth set <bootmeth> <property> <value> - set optional property
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Description
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-----------
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The `bootmeth` command is used to manage bootmeths. It can list them and change
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the order in which they are used.
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See :doc:`/develop/bootstd/index` for more information.
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.. _bootmeth_order:
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bootmeth order
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~~~~~~~~~~~~~~
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Selects which bootmeths to use and the order in which they are invoked. When
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scanning bootdevs, each bootmeth is tried in turn to see if it can find a valid
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bootflow. You can use this command to adjust the order or even to omit some
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boomeths.
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The argument is a quoted list of bootmeths to use, by name. If global bootmeths
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are included, they must be at the end, otherwise the scanning mechanism will not
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work correctly.
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bootmeth list
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~~~~~~~~~~~~~
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This lists the selected bootmeths, or all of them, if the `-a` flag is used.
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The format looks like this:
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===== === ================== =================================
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Order Seq Name Description
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===== === ================== =================================
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0 0 extlinux Extlinux boot from a block device
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1 1 efi EFI boot from an .efi file
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2 2 pxe PXE boot from a network device
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3 3 sandbox Sandbox boot for testing
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glob 4 efi_mgr EFI bootmgr flow
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===== === ================== =================================
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The fields are as follows:
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Order:
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The order in which these bootmeths are invoked for each bootdev. If this
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shows as a hyphen, then the bootmeth is not in the current ordering. If it
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shows as 'glob', then this is a global bootmeth and should be at the end.
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Seq:
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The sequence number of the bootmeth, i.e. the normal ordering if none is set
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Name:
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Name of the bootmeth
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Description:
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A friendly description for the bootmeth
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Example
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-------
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This shows listing bootmeths. All are present and in the normal order::
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=> bootmeth list
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Order Seq Name Description
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----- --- ------------------ ------------------
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0 0 distro Extlinux boot from a block device
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1 1 efi EFI boot from an .efi file
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2 2 pxe PXE boot from a network device
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3 3 sandbox Sandbox boot for testing
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4 4 efi_mgr EFI bootmgr flow
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----- --- ------------------ ------------------
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(5 bootmeths)
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Now the order is changed, to include only two of them::
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=> bootmeth order "sandbox distro"
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=> bootmeth list
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Order Seq Name Description
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----- --- ------------------ ------------------
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0 3 sandbox Sandbox boot for testing
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1 0 distro Extlinux boot from a block device
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----- --- ------------------ ------------------
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(2 bootmeths)
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The -a flag shows all bootmeths so you can clearly see which ones are used and
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which are not::
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=> bootmeth list -a
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Order Seq Name Description
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----- --- ------------------ ------------------
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1 0 distro Extlinux boot from a block device
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- 1 efi EFI boot from an .efi file
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- 2 pxe PXE boot from a network device
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0 3 sandbox Sandbox boot for testing
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- 4 efi_mgr EFI bootmgr flow
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----- --- ------------------ ------------------
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(5 bootmeths)
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bootmeth set
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~~~~~~~~~~~~
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Allows setting of bootmeth specific configuration. This allows finer grain
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control over the boot process in specific instances.
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Supported Configuration Options
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-------------------------------
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The following configuration options are currently supported:
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======== =================== ====== ===============================
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Property Supported Bootmeths Values Description
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======== =================== ====== ===============================
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fallback extlinux 0 | 1 Enable or disable fallback path
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======== =================== ====== ===============================
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Bootmeth set Example
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--------------------
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With the bootcount functionality enabled, when the bootlimit is reached, the
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`altbootcmd` environment variable lists the command used for booting rather
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than `bootcmd`. We can set the fallback configuration to cause the fallback
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boot option to be preferred, to revert to a previous known working boot option
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after a failed update for example. So if `bootcmd` is set to::
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bootflow scan -lb
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We would set "altbootcmd" to::
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bootmeth set extlinux fallback 1; bootflow scan -lb
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