this signal the systemd manager will reexecute itself. This is mostly equivalent to systemctl daemon-reexec except that it will be done asynchronously.

           The systemd system manager treats this signal the same way as SIGTERM.

       SIGRTMIN+26
           Restores the log target to its configured value. The configured value is derived from – in order of priority – the value specified with systemd.log-target= on the kernel command line, or the value specified with
           LogTarget= in the configuration file, or the built-in default.

       SIGRTMIN+27, SIGRTMIN+28
           Sets the log target to "console" on SIGRTMIN+27 (or "kmsg" on SIGRTMIN+28), in a fashion equivalent to systemd.log_target=console (or systemd.log_target=kmsg on SIGRTMIN+28) on the kernel command line.

ENVIRONMENT
       The environment block for the system manager is initially set by the kernel. (In particular, "key=value" assignments on the kernel command line are turned into environment variables for PID 1). For the user manager,
       the system manager sets the environment as described in the "Environment Variables in Spawned Processes" section of systemd.exec(5). The DefaultEnvironment= setting in the system manager applies to all services
       including user@.service. Additional entries may be configured (as for any other service) through the Environment= and EnvironmentFile= settings for user@.service (see systemd.exec(5)). Also, additional environment
       variables may be set through the ManagerEnvironment= setting in systemd‐system.conf(5) and systemd‐user.conf(5).

       Some of the variables understood by systemd:

       $SYSTEMD_LOG_LEVEL
           The maximum log level of emitted messages (messages with a higher log level, i.e. less important ones, will be suppressed). Either one of (in order of decreasing importance) emerg, alert, crit, err, warning,
           notice, info, debug, or an integer in the range 0...7. See syslog(3) for more information.

           This can be overridden with --log-level=.

       $SYSTEMD_LOG_COLOR
           A boolean. If true, messages written to the tty will be colored according to priority.

           This can be overridden with --log-color=.

       $SYSTEMD_LOG_TIME
           A boolean. If true, console log messages will be prefixed with a timestamp.

           This can be overridden with --log-time=.

       $SYSTEMD_LOG_LOCATION
           A boolean. If true, messages will be prefixed with a filename and line number in the source code where the message originates.

           This can be overridden with --log-location=.

       $SYSTEMD_LOG_TID
           A boolean. If true, messages will be prefixed with the current numerical thread ID (TID).

       $SYSTEMD_LOG_TARGET
           The destination for log messages. One of console (log to the attached tty), console-prefixed (log to the attached tty but with prefixes encoding the log level and "facility", see syslog(3), kmsg (log to the kernel
           circular log buffer), journal (log to the journal), journal-or-kmsg (log to the journal if available, and to kmsg otherwise), auto (determine the appropriate log target automatically, the default), null (disable
           log output).

           This can be overridden with --log-target=.

       $XDG_CONFIG_HOME, $XDG_CONFIG_DIRS, $XDG_DATA_HOME, $XDG_DATA_DIRS
           The systemd user manager uses these variables in accordance to the XDG Base Directory specification[6] to find its configuration.

       $SYSTEMD_UNIT_PATH, $SYSTEMD_GENERATOR_PATH, $SYSTEMD_ENVIRONMENT_GENERATOR_PATH
           Controls where systemd looks for unit files and generators.

           These variables may contain a list of paths, separated by colons (":"). When set, if the list ends with an empty component ("...:"), this list is prepended to the usual set of paths. Otherwise, the specified list
           replaces the usual set of paths.

       $SYSTEMD_PAGER
           Pager to use when --no-pager