126 lines
6.9 KiB
XML
126 lines
6.9 KiB
XML
<?xml version="1.0"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refsect1>
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<title>Environment</title>
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<variablelist class='environment-variables'>
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<varlistentry id='pager'>
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<term><varname>$SYSTEMD_PAGER</varname></term>
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<listitem><para>Pager to use when <option>--no-pager</option> is not given; overrides
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<varname>$PAGER</varname>. If neither <varname>$SYSTEMD_PAGER</varname> nor <varname>$PAGER</varname> are set, a
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set of well-known pager implementations are tried in turn, including
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<citerefentry project='man-pages'><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry> and
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<citerefentry project='man-pages'><refentrytitle>more</refentrytitle><manvolnum>1</manvolnum></citerefentry>, until one is found. If
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no pager implementation is discovered no pager is invoked. Setting this environment variable to an empty string
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or the value <literal>cat</literal> is equivalent to passing <option>--no-pager</option>.</para></listitem>
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</varlistentry>
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<varlistentry id='less'>
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<term><varname>$SYSTEMD_LESS</varname></term>
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<listitem><para>Override the options passed to <command>less</command> (by default
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<literal>FRSXMK</literal>).</para>
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<para>Users might want to change two options in particular:</para>
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<variablelist>
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<varlistentry>
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<term><option>K</option></term>
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<para>This option instructs the pager to exit immediately when
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<keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo> is pressed. To allow
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<command>less</command> to handle <keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo>
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itself to switch back to the pager command prompt, unset this option.</para>
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<para>If the value of <varname>$SYSTEMD_LESS</varname> does not include <literal>K</literal>,
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and the pager that is invoked is <command>less</command>,
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<keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo> will be ignored by the
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executable, and needs to be handled by the pager.</para>
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</varlistentry>
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<varlistentry>
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<term><option>X</option></term>
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<para>This option instructs the pager to not send termcap initialization and deinitialization
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strings to the terminal. It is set by default to allow command output to remain visible in the
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terminal even after the pager exits. Nevertheless, this prevents some pager functionality from
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working, in particular paged output cannot be scrolled with the mouse.</para>
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</varlistentry>
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</variablelist>
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<para>See
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<citerefentry project='man-pages'><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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for more discussion.</para></listitem>
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</varlistentry>
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<varlistentry id='lesscharset'>
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<term><varname>$SYSTEMD_LESSCHARSET</varname></term>
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<listitem><para>Override the charset passed to <command>less</command> (by default <literal>utf-8</literal>, if
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the invoking terminal is determined to be UTF-8 compatible).</para></listitem>
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</varlistentry>
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<varlistentry id='lesssecure'>
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<term><varname>$SYSTEMD_PAGERSECURE</varname></term>
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<listitem><para>Takes a boolean argument. When true, the "secure" mode of the pager is enabled; if
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false, disabled. If <varname>$SYSTEMD_PAGERSECURE</varname> is not set at all, secure mode is enabled
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if the effective UID is not the same as the owner of the login session, see <citerefentry
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project='man-pages'><refentrytitle>geteuid</refentrytitle><manvolnum>2</manvolnum></citerefentry> and
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<citerefentry><refentrytitle>sd_pid_get_owner_uid</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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In secure mode, <option>LESSSECURE=1</option> will be set when invoking the pager, and the pager shall
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disable commands that open or create new files or start new subprocesses. When
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<varname>$SYSTEMD_PAGERSECURE</varname> is not set at all, pagers which are not known to implement
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secure mode will not be used. (Currently only
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<citerefentry><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry> implements
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secure mode.)</para>
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<para>Note: when commands are invoked with elevated privileges, for example under <citerefentry
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project='man-pages'><refentrytitle>sudo</refentrytitle><manvolnum>8</manvolnum></citerefentry> or
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<citerefentry
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project='die-net'><refentrytitle>pkexec</refentrytitle><manvolnum>1</manvolnum></citerefentry>, care
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must be taken to ensure that unintended interactive features are not enabled. "Secure" mode for the
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pager may be enabled automatically as describe above. Setting <varname>SYSTEMD_PAGERSECURE=0</varname>
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or not removing it from the inherited environment allows the user to invoke arbitrary commands. Note
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that if the <varname>$SYSTEMD_PAGER</varname> or <varname>$PAGER</varname> variables are to be
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honoured, <varname>$SYSTEMD_PAGERSECURE</varname> must be set too. It might be reasonable to completely
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disable the pager using <option>--no-pager</option> instead.</para></listitem>
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</varlistentry>
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<varlistentry id='colors'>
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<term><varname>$SYSTEMD_COLORS</varname></term>
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<listitem><para>Takes a boolean argument. When true, <command>systemd</command> and related utilities
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will use colors in their output, otherwise the output will be monochrome. Additionally, the variable can
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take one of the following special values: <literal>16</literal>, <literal>256</literal> to restrict the use
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of colors to the base 16 or 256 ANSI colors, respectively. This can be specified to override the automatic
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decision based on <varname>$TERM</varname> and what the console is connected to.</para></listitem>
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</varlistentry>
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<!-- This is not documented on purpose, because it is not clear if $NO_COLOR will become supported
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widely enough. So let's provide support, but without advertising this.
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<varlistentry id='no-color'>
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<term><varname>$NO_COLOR</varname></term>
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<listitem><para>If set (to any value), and <varname>$SYSTEMD_COLORS</varname> is not set, equivalent to
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<option>SYSTEMD_COLORS=0</option>. See <ulink url="https://no-color.org/">no-color.org</ulink>.</para>
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</listitem>
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</varlistentry>
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-->
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<varlistentry id='urlify'>
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<term><varname>$SYSTEMD_URLIFY</varname></term>
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<listitem><para>The value must be a boolean. Controls whether clickable links should be generated in
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the output for terminal emulators supporting this. This can be specified to override the decision that
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<command>systemd</command> makes based on <varname>$TERM</varname> and other conditions.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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