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="/lib/firmware/"
           This variable specifies the unversioned stem of paths where U-BOOT  should  look  for  the  flattened
           device  tree  binaries.  Default is '/lib/firmware/'. When U_BOOT_SYNC_DTBS is true and u-boot-update
           detects /boot is on a separate partition, the default value is then '/dtb-'.

       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'.

       U_BOOT_SYNC_DTBS="true|false"
           This variable specifies if u-boot-update should automatically attempt to copy device tree binaries to
           /boot in case it is on a different partition than /.  Values are either 'true' or 'false', default is
           'false'.

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.