locale.conf — Configuration file for locale settings
/etc/locale.conf
The /etc/locale.conf file configures
    system-wide locale settings. It is read at early boot by
    systemd(1).
The basic file format of locale.conf is
    a newline-separated list of environment-like shell-compatible
    variable assignments. It is possible to source the configuration
    from shell scripts, however, beyond mere variable assignments, no
    shell features are supported, allowing applications to read the
    file without implementing a shell compatible execution
    engine.
Note that the kernel command line options
    locale.LANG=,
    locale.LANGUAGE=,
    locale.LC_CTYPE=,
    locale.LC_NUMERIC=,
    locale.LC_TIME=,
    locale.LC_COLLATE=,
    locale.LC_MONETARY=,
    locale.LC_MESSAGES=,
    locale.LC_PAPER=,
    locale.LC_NAME=,
    locale.LC_ADDRESS=,
    locale.LC_TELEPHONE=,
    locale.LC_MEASUREMENT=,
    locale.LC_IDENTIFICATION= may be
    used to override the locale settings at boot.
The locale settings configured in
    /etc/locale.conf are system-wide and are
    inherited by every service or user, unless overridden or unset by
    individual programs or individual users.
Depending on the operating system, other configuration files might be checked for locale configuration as well, however only as fallback.
/etc/locale.conf is usually created and updated
    using
    systemd-localed.service(8).
    localectl(1)
    may be used to alter the settings in this file during runtime from
    the command line. Use
    systemd-firstboot(1)
    to initialize them on mounted (but not booted) system images.
The following locale settings may be set using
    /etc/locale.conf:
    LANG=,
    LANGUAGE=,
    LC_CTYPE=,
    LC_NUMERIC=,
    LC_TIME=,
    LC_COLLATE=,
    LC_MONETARY=,
    LC_MESSAGES=,
    LC_PAPER=,
    LC_NAME=,
    LC_ADDRESS=,
    LC_TELEPHONE=,
    LC_MEASUREMENT=,
    LC_IDENTIFICATION=.
    Note that LC_ALL may not be configured in this
    file. For details about the meaning and semantics of these
    settings, refer to
    locale(7).
Example 1. German locale with English messages
/etc/locale.conf:
LANG=de_DE.UTF-8 LC_MESSAGES=en_US.UTF-8