environment.d

systemd

environment.d

5

environment.d

Definition of user service environment

~/.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.

The user-level configuration directory defaults to ~/.config/environment.d/. If $XDG_CONFIG_HOME is set to an absolute path in the user service manager environment (e.g. via PAM or /etc/environment), it takes precedence over ~/.config/. Note that this creates a bootstrapping consideration: variables set in environment.d/ files, including $XDG_CONFIG_HOME itself, are not available when the generator determines which directory to read.

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 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. You can escape a literal dollar sign $ by doubling it, as in $$.

A backslash character \ followed by a newline acts as a line continuation (both characters are discarded); in all other cases, the backslash is consumed and the following character is included literally in the value. This can be used to preserve leading/trailing whitespace or include literal backslashes.

You may optionally enclose the right hand side of assignments in pairs of either 'single quotes' or "double quotes"; these will be stripped from the value before saving it. Using either quoting style does not affect variable expansion; however, single quotes disable backslash escaping entirely, while double quoting removes backslashes that precede double quotes ", dollar signs $, backslashes \, backticks `, and newlines, and leaves all other backslashes in place.

Leading and trailing whitespace characters are stripped from both the left and right hand sides of the assignment. To preserve such spaces in the value, you can either enclose the entire value in quotes, or escape the space characters with backslashes. You can also include literal newlines in the value by enclosing it in quotes.

Each <KEY> must be a valid variable name. Empty lines and lines beginning with the comment characters # or ; are ignored. No other elements of shell syntax are supported.

Examples

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/}

# A comment
test_var=(variable)
; Another comment
test_comment=value # This is a part of the variable, and not a comment!

test_none= \ before\
after "" '' \${test_var}
test_double=" \ before\
after "" '' \${test_var}"
test_single=' \ before\
after "" '' \${test_var}'

# The above example produces the following environment variables, written using
# C-style string escapes:
#
# test_var="(variable)"
# test_comment="value # This is a part of the variable, and not a comment!"
# test_none=" beforeafter \"\" '' (variable)"
# test_double=" \\ beforeafter  '' (variable)"
# test_single=" \\ before\\\nafter \"\"  \\(variable)"

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.

See Also

systemd(1), systemd-environment-d-generator(8), systemd.environment-generator(7)