1.9. Default environment version 2

barebox stores its environment files under the top-level /env/ directory, where most of the runtime configuration scripts are located. This environment is comparable to a tar archive which is unpacked from a storage medium during startup. If for whatever reason the environment cannot be loaded from a storage medium, a compiled-in default environment is used instead.

The environment is not automatically stored on the storage medium when a file under /env/ is changed; rather, this has to be done manually using the saveenv - save environment to persistent storage command.

There are two sets of generic environment files which can be used. The older version (version one) should not be used for new boards and is not described here (even though there are still numerous board definitions that use it). All new boards should use defaultenv-2 exclusively.

The default environment is composed from different directories during compilation:

defaultenv/defaultenv-2-base                 -> base files
defaultenv/defaultenv-2-dfu                  -> overlay for DFU
defaultenv/defaultenv-2-reboot-mode          -> overlay for reboot modes
defaultenv/defaultenv-2-menu                 -> overlay for menus
arch/$ARCH/boards/<board>/defaultenv-<board> -> board specific overlay
$(CONFIG_DEFAULT_ENVIRONMENT_PATH)           -> config specific overlay

The content of the above directories is applied one after another. If the same file exists in a later overlay, it will overwrite the preceding one. The board specific overlay, or overlays, could be at any path, but usually follows the form given. They must be added to a Makefile in bbenv-y and defaultenv_append_directory() used to add them in board init code.

Note that not all of the above directories will necessarily be included in your default environment, it depends on your barebox configuration settings. You can see the configuration variables and their respective included directories in defaultenv/Makefile:

bbenv-$(CONFIG_DEFAULT_ENVIRONMENT_GENERIC_NEW) += defaultenv-2-base

1.9.1. /env/bin/init

This script is executed by the barebox startup code after initialization. In defaultenv-2, this script will define and set a number of global variables, followed by sourcing all of the scripts in /env/init/ with:

for i in /env/init/*; do
        . $i

This script is also responsible for defining the boot timeout value (by default, three seconds), then printing the timeout prompt for the user. Be careful making changes to this script: since it is executed before any user intervention, it might lock the system.

1.9.2. /env/init/

The /env/init/ directory is the location for startup scripts. The scripts in this directory will be executed in alphabetical order by the /env/bin/init script described earlier.

1.9.3. /env/boot/

The /env/boot/ directory contains boot entry scripts. The boot - boot from script, device, … command treats the files in this directory as possible boot targets. See Booting Linux for more details.

1.9.4. /env/config

This file contains some basic configuration settings. It can be edited using the edit - a small full-screen editor command. Typical content:


# change network settings in /env/network/eth0
# change mtd partition settings and automountpoints in /env/init/*


# set to false if you do not want to have colors

# user (used for network filenames)

# timeout in seconds before the default boot entry is started

# key to abort autoboot. Supported options are: "any" and "ctrl-c"

# list of boot entries. These are executed in order until one
# succeeds. An entry can be:
# - a filename in /env/boot/
# - a full path to a directory. All files in this directory are
#   treated as boot files and executed in alphabetical order

# base bootargs

When changing this file remember to do a saveenv to make the change persistent. Also it may be necessary to manually source /env/config before the changes take effect.

1.9.5. /env/network/

This contains the configuration files for the network interfaces. Typically there will be a file eth0 with a content like this:


# ip setting (static/dhcp)

# static setup used if ip=static

# MAC address if needed

# put code to discover eth0 (i.e. 'usb') to /env/network/eth0-discover

exit 0

1.9.6. /env/bmode/

This contains the files to be sourced when barebox detects that the OS had requested a specific Reboot Mode (via e.g. reboot bootloader under Linux). After the /env/init scripts were executed, barebox will source /env/bmode/${global.system.reboot_mode.prev} if available.