Ubuntu Manpage: environment.d - Definition of user service environment

Provided by: systemd_256.5-2ubuntu3.1_amd64

NAME

       environment.d - Definition of user service environment

SYNOPSIS

           ~/.config/environment.d/*.conf
           /etc/environment.d/*.conf
           /run/environment.d/*.conf
           /usr/local/lib/environment.d/*.conf
           /usr/lib/environment.d/*.conf
           /etc/environment

DESCRIPTION

       Configuration files in the environment.d/ directories contain lists of environment
       variable assignments passed to services started by the systemd user instance.  systemd-
       environment-d-generator(8) parses them and updates the environment exported by the systemd
       user instance. See below for an discussion of which processes inherit those variables.

       It is recommended to use numerical prefixes for file names to simplify ordering.

       For backwards compatibility, a symlink to /etc/environment is installed, so this file is
       also parsed.

CONFIGURATION DIRECTORIES AND PRECEDENCE

Configuration files are read from directories in /etc/, /run/, /usr/local/lib/, and
/usr/lib/, in order of precedence, as listed in the SYNOPSIS section above. Files must
have the ".conf" extension. Files in /etc/ override files with the same name in /run/,
/usr/local/lib/, and /usr/lib/. Files in /run/ override files with the same name under
/usr/.

All configuration files are sorted by their filename in lexicographic order, regardless of
which of the directories they reside in. If multiple files specify the same option, the
entry in the file with the lexicographically latest name will take precedence. Thus, the
configuration in a certain file may either be replaced completely (by placing a file with
the same name in a directory with higher priority), or individual settings might be
changed (by specifying additional settings in a file with a different name that is ordered
later).

Packages should install their configuration files in /usr/lib/ (distribution packages) or
/usr/local/lib/ (local installs) [1]. Files in /etc/ are reserved for the local
administrator, who may use this logic to override the configuration files installed by
vendor packages.

It is recommended to prefix all filenames with a two-digit number and a dash to simplify
the ordering. It is recommended to use the range 10-40 for configuration files in /usr/
and the range 60-90 for configuration files in /etc/ and /run/, to make sure that local
and transient configuration files will always take priority over configuration files
shipped by the OS vendor.

If the administrator wants to disable a configuration file supplied by the vendor, the
recommended way is to place a symlink to /dev/null in the configuration directory in
/etc/, with the same filename as the vendor configuration file. If the vendor
configuration file is included in the initrd image, the image has to be regenerated.

CONFIGURATION FORMAT

       The configuration files contain a list of "KEY=VALUE" environment variable assignments,
       separated by newlines. The right hand side of these assignments may reference previously
       defined environment variables, using the "${OTHER_KEY}" and "$OTHER_KEY" format. It is
       also possible to use "${FOO:-DEFAULT_VALUE}" to expand in the same way as "${FOO}" unless
       the expansion would be empty, in which case it expands to DEFAULT_VALUE, and use
       "${FOO:+ALTERNATE_VALUE}" to expand to ALTERNATE_VALUE as long as "${FOO}" would have
       expanded to a non-empty value. No other elements of shell syntax are supported.

       Each KEY must be a valid variable name. Empty lines and lines beginning with the comment
       character "#" are ignored.

   Example
       Example 1. Setup environment to allow access to a program installed in /opt/foo

       /etc/environment.d/60-foo.conf:

                   FOO_DEBUG=force-software-gl,log-verbose
                   PATH=/opt/foo/bin:$PATH
                   LD_LIBRARY_PATH=/opt/foo/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
                   XDG_DATA_DIRS=/opt/foo/share:${XDG_DATA_DIRS:-/usr/local/share/:/usr/share/}

APPLICABILITY

Environment variables exported by the user service manager (systemd --user instance
started in the user@uid.service system service) are passed to any services started by that
service manager. In particular, this may include services which run user shells. For
example in the GNOME environment, the graphical terminal emulator runs as the
gnome-terminal-server.service user unit, which in turn runs the user shell, so that shell
will inherit environment variables exported by the user manager. For other instances of
the shell, not launched by the user service manager, the environment they inherit is
defined by the program that starts them. Hint: in general, systemd.service(5) units
contain programs launched by systemd, and systemd.scope(5) units contain programs launched
by something else.

Note that these files do not affect the environment block of the service manager itself,
but exclusively the environment blocks passed to the services it manages. Environment
variables set that way thus cannot be used to influence behaviour of the service manager.
In order to make changes to the service manager's environment block the environment must
be modified before the user's service manager is invoked, for example from the system
service manager or via a PAM module.

Specifically, for ssh logins, the sshd(8) service builds an environment that is a
combination of variables forwarded from the remote system and defined by sshd, see the
discussion in ssh(1). A graphical display session will have an analogous mechanism to
define the environment. Note that some managers query the systemd user instance for the
exported environment and inject this configuration into programs they start, using
systemctl show-environment or the underlying D-Bus call.

NOTES

        1. 💣💥🧨💥💥💣 Please note that those configuration files must be available at all times.
           If /usr/local/ is a separate partition, it may not be available during early boot, and
           must not be used for configuration.