$SYSTEMD_LOG_LEVEL The maximum log level of emitted messages (messages with a higher log level, i.e. less important ones, will be suppressed). Takes a comma-separated list of values. A value may be 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 syslog3 for more information. Each value may optionally be prefixed with one of console, syslog, kmsg or journal followed by a colon to set the maximum log level for that specific log target (e.g. SYSTEMD_LOG_LEVEL=debug,console:info specifies to log at debug level except when logging to the console which should be at info level). Note that the global maximum log level takes priority over any per target maximum log levels. $SYSTEMD_LOG_COLOR A boolean. If true, messages written to the tty will be colored according to priority. This setting is only useful when messages are written directly to the terminal, because journalctl1 and other tools that display logs will color messages based on the log level on their own. $SYSTEMD_LOG_TIME A boolean. If true, console log messages will be prefixed with a timestamp. This setting is only useful when messages are written directly to the terminal or a file, because journalctl1 and other tools that display logs will attach timestamps based on the entry metadata on their own. $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. Note that the log location is often attached as metadata to journal entries anyway. Including it directly in the message text can nevertheless be convenient when debugging programs. $SYSTEMD_LOG_TID A boolean. If true, messages will be prefixed with the current numerical thread ID (TID). Note that the this information is attached as metadata to journal entries anyway. Including it directly in the message text can nevertheless be convenient when debugging programs. $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 syslog3, 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). $SYSTEMD_LOG_RATELIMIT_KMSG Whether to ratelimit kmsg or not. Takes a boolean. Defaults to true. If disabled, systemd will not ratelimit messages written to kmsg. $SYSTEMD_PAGER $PAGER Pager to use when --no-pager is not given. $SYSTEMD_PAGER is used if set; otherwise $PAGER is used. If neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known pager implementations is tried in turn, including less1 and more1, until one is found. If no pager implementation is discovered, no pager is invoked. Setting those environment variables to an empty string or the value cat is equivalent to passing --no-pager. Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER and $PAGER can only be used to disable the pager (with cat or ), and are otherwise ignored. $SYSTEMD_LESS Override the options passed to less (by default FRSXMK). Users might want to change two options in particular: K This option instructs the pager to exit immediately when CtrlC is pressed. To allow less to handle CtrlC itself to switch back to the pager command prompt, unset this option. If the value of $SYSTEMD_LESS does not include K, and the pager that is invoked is less, CtrlC will be ignored by the executable, and needs to be handled by the pager. X This option instructs the pager to not send termcap initialization and deinitialization strings to the terminal. It is set by default to allow command output to remain visible in the terminal even after the pager exits. Nevertheless, this prevents some pager functionality from working, in particular paged output cannot be scrolled with the mouse. Note that setting the regular $LESS environment variable has no effect for less invocations by systemd tools. See less1 for more discussion. $SYSTEMD_LESSCHARSET Override the charset passed to less (by default utf-8, if the invoking terminal is determined to be UTF-8 compatible). Note that setting the regular $LESSCHARSET environment variable has no effect for less invocations by systemd tools. $SYSTEMD_PAGERSECURE Common pager commands like less1, in addition to "paging", i.e. scrolling through the output, support opening of or writing to other files and running arbitrary shell commands. When commands are invoked with elevated privileges, for example under sudo8 or pkexec1, the pager becomes a security boundary. Care must be taken that only programs with strictly limited functionality are used as pagers, and unintended interactive features like opening or creation of new files or starting of subprocesses are not allowed. "Secure mode" for the pager may be enabled as described below, if the pager supports that (most pagers are not written in a way that takes this into consideration). It is recommended to either explicitly enable "secure mode" or to completely disable the pager using --no-pager or PAGER=cat when allowing untrusted users to execute commands with elevated privileges. This option takes a boolean argument. When set to true, the "secure mode" of the pager is enabled. In "secure mode", LESSSECURE=1 will be set when invoking the pager, which instructs the pager to disable commands that open or create new files or start new subprocesses. Currently only less1 is known to understand this variable and implement "secure mode". When set to false, no limitation is placed on the pager. Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited environment may allow the user to invoke arbitrary commands. When $SYSTEMD_PAGERSECURE is not set, systemd tools attempt to automatically figure out if "secure mode" should be enabled and whether the pager supports it. "Secure mode" is enabled if the effective UID is not the same as the owner of the login session, see geteuid2 and sd_pid_get_owner_uid3, or when running under sudo8 or similar tools ($SUDO_UID is set It is recommended for other tools to set and check $SUDO_UID as appropriate, treating it is a common interface.). In those cases, SYSTEMD_PAGERSECURE=1 will be set and pagers which are not known to implement "secure mode" will not be used at all. Note that this autodetection only covers the most common mechanisms to elevate privileges and is intended as convenience. It is recommended to explicitly set $SYSTEMD_PAGERSECURE or disable the pager. Note that if the $SYSTEMD_PAGER or $PAGER variables are to be honoured, other than to disable the pager, $SYSTEMD_PAGERSECURE must be set too. $SYSTEMD_COLORS Takes a boolean argument. When true, systemd and related utilities will use colors in their output, otherwise the output will be monochrome. Additionally, the variable can take one of the following special values: 16, 256 to restrict the use of colors to the base 16 or 256 ANSI colors, respectively. This can be specified to override the automatic decision based on $TERM and what the console is connected to. $SYSTEMD_URLIFY The value must be a boolean. Controls whether clickable links should be generated in the output for terminal emulators supporting this. This can be specified to override the decision that systemd makes based on $TERM and other conditions.