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.

       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 'ro earlycon' (except for recovery entries, where quiet is avoided).

       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'.

FILES

       /etc/default/u-boot

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.

1.00                                               2017-10-18                                   U-BOOT-UPDATE(8)