NAME

       u-boot-update - program to generate u-boot menu files

SYNOPSIS

       u-boot-update

DESCRIPTION

       u-boot-update  is  a  tool  used to generate the menu files used by the U-BOOT bootloader.
       Options can be configured in /etc/default/u-boot or by adding configuration fragment files
       to  /usr/share/u-boot-menu/conf.d/ (those take precedence over /etc/default/u-boot) and/or
       to /etc/u-boot-menu/conf.d/ (those take precedence over the 2 aforementioned locations).

       In order to avoid situations where the system might be rendered unbootable  by  a  package
       removal,  other  packages and downstream distributions MUST NOT edit or modify files under
       /etc as those are meant for use by end-users  only.  Instead,  it  is  mandated  for  such
       packages to install their config fragments ONLY under /usr/share/u-boot-menu/conf.d/.

       For each <version> of linux kernel installed, menu items for each of <U_BOOT_ALTERNATIVES>
       are generated for the first valid entry among these:

       • fdt <U_BOOT_FDT_DIR><version>/<U_BOOT_FDT>

       • fdtdir <U_BOOT_FDT_DIR><version>/

       • fdt /<U_BOOT_FDT>

       • fdt /dtb-<version>

       Paths without <U_BOOT_FDT_DIR> are considered only when <U_BOOT_FDT_DIR> is  left  at  its
       default value.

       When  root  (/)  and  boot (/boot) are mounted on separate filesystems, paths are examined
       with /boot prepended (i.e. variables should be defined without it).

OPTIONS

       U_BOOT_UPDATE="true|false"
           This variable specifies if u-boot-update is allowed to modify the configuration  files
           in /boot/extlinux.  Values are either 'true' or 'false', default is 'true'.

       U_BOOT_ALTERNATIVES="default recovery"
           This  variable  specifies  which  entries  u-boot-update  is  populating.   Values are
           'default', 'recovery', 'live', default is 'default recovery'.

       U_BOOT_DEFAULT="l0"
           This variable specifies the default entry to boot.  The name of an entry  consists  of
           two  or  three characters.  Linux kernel images start with the letter 'l', followed by
           an integer started by '0' for the first  kernel  version  (which  is  numerically  the
           highest  one  in case kernel images of more than one linux version are installed) and,
           optionally, the mode (r for rescue mode, l for live mode).  Memdisk entries start with
           the  letter  'm', followed by an integer, no optional modes available.  The default is
           'l0'.

       U_BOOT_ENTRIES="all"
           This variables specifies how many kernel versions should be used to populate the  boot
           configuration.   Value  is  an  integer  starting with 1, or 'all' to populate for all
           kernels, default is 'all'.

       U_BOOT_MENU_LABEL="Debian GNU/Linux, kernel"
           This variable specifies the text that is used as  a  description  in  the  boot  menu.
           Value  is  an arbitrary string.  If not specified, PRETTY_NAME from /etc/os-release is
           used.  Otherwise, it defaults to 'Debian GNU/Linux, kernel'.

       U_BOOT_PARAMETERS="ro earlycon"
           This variable specifies additional boot parameters that are appended  to  each  kernel
           entry.   Value is an arbitrary string, default is the contents of /etc/kernel/cmdline,
           or 'ro earlycon' (except for recovery entries, where quiet is avoided) if this file is
           not present or empty.

       U_BOOT_ROOT="root=DEVICE"
           This  variable  specifies  the  root  partition.   It  is automatically extracted from
           /etc/fstab.  U-BOOT supports both devices and UUIDs.

       U_BOOT_TIMEOUT="50"
           This variable specifies the time that U-BOOT should wait for user input  during  boot.
           Values  are  in  decisecond  greater  than  0  (e.g.  '10'  for a 1 second timeout), 0
           specifies to wait forever.  The default is 50.

       U_BOOT_FDT_DIR="/usr/lib/linux-image-"
           This variable specifies the unversioned stem of paths where U-BOOT should look for the
           flattened device tree binaries.  Default is '/usr/lib/linux-image-'.

       U_BOOT_FDT="device-tree.dtb"
           This  variable  specifies  filename  or trailing part of path for a single device tree
           binary.  Default is 'device-tree.dtb'.

       U_BOOT_FDT_OVERLAYS_DIR="/boot/dtbo"
           This variable specifies the unversioned stem of paths where U-BOOT should look for the
           flattened device tree overlays binaries.  Default is '/boot/dtbo/'.

       U_BOOT_FDT_OVERLAYS="device-tree.dtbo"
           This  variable  specifies  filenames  or trailing part of path for device tree overlay
           binaries.  Default is not set.

       U_BOOT_INITRD="initrd.img"
           This variable specifies the unversioned stem  of  initramfs  filename.   If  versioned
           filename  exists  (e.g.  'initrd.img-5.10.0-8-armmp-lpae')  then  this filename set as
           option 'initrd', otherwise if unversioned filename exists (e.g. 'initrd.img) then that
           is  set  as  option  'initrd',  otherwise  option  'initrd'  is  not  set.  Default is
           'initrd.img'.

FILES

       /etc/default/u-boot /usr/share/u-boot-menu/conf.d/ /etc/u-boot-menu/conf.d/

HOMEPAGE

       More information about U-BOOT can be found at <http://www.denx.de/wiki/U-Boot>.

       u-boot-update and this manual page was written by Daniel Baumann <daniel.baumann@progress-
       technologies.net>  for extlinux.  Riku Voipio <riku.voipio@linaro.org> updated them for u-
       boot.  Jonas Smedegaard <dr@jones.dk> updated misc. later changes.