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253 lines
11 KiB
XML
253 lines
11 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/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-ask-password"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-ask-password</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-ask-password</refentrytitle>
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<manvolnum>1</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-ask-password</refname>
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<refpurpose>Query the user for a system password</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>systemd-ask-password <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt">MESSAGE</arg></command>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>systemd-ask-password</command> may be used to query
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a system password or passphrase from the user, using a question
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message specified on the command line. When run from a TTY it will
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query a password on the TTY and print it to standard output. When
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run with no TTY or with <option>--no-tty</option> it will use the
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system-wide query mechanism, which allows active users to respond via
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several agents, listed below.</para>
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<para>The purpose of this tool is to query system-wide passwords
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— that is passwords not attached to a specific user account.
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Examples include: unlocking encrypted hard disks when they are
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plugged in or at boot, entering an SSL certificate passphrase for
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web and VPN servers.</para>
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<para>Existing agents are:
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<itemizedlist>
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<listitem><para>A boot-time password agent asking the user for
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passwords using
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<citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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</para></listitem>
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<listitem><para>A boot-time password agent querying the user
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directly on the console —
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<citerefentry><refentrytitle>systemd-ask-password-console.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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</para></listitem>
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<listitem><para>An agent requesting password input via a
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<citerefentry project='man-pages'><refentrytitle>wall</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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message —
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<citerefentry><refentrytitle>systemd-ask-password-wall.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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</para></listitem>
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<listitem><para>A TTY agent that is temporarily spawned during
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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invocations,</para></listitem>
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<listitem><para>A command line agent which can be started
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temporarily to process queued password
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requests — <command>systemd-tty-ask-password-agent --query</command>.
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</para></listitem>
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</itemizedlist></para>
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<para>Answering system-wide password queries is a privileged operation, hence
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all the agents listed above (except for the last one), run as privileged
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system services. The last one also needs elevated privileges, so
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should be run through
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<citerefentry project='die-net'><refentrytitle>sudo</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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or similar.</para>
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<para>Additional password agents may be implemented according to
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the <ulink url="https://systemd.io/PASSWORD_AGENTS/">systemd Password Agent
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Specification</ulink>.</para>
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<para>If a password is queried on a TTY, the user may press TAB to
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hide the asterisks normally shown for each character typed.
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Pressing Backspace as first key achieves the same effect.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The following options are understood:</para>
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<variablelist>
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<varlistentry>
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<term><option>--icon=</option></term>
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<listitem><para>Specify an icon name alongside the password
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query, which may be used in all agents supporting graphical
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display. The icon name should follow the <ulink
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url="http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html">XDG
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Icon Naming Specification</ulink>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--id=</option></term>
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<listitem><para>Specify an identifier for this password
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query. This identifier is freely choosable and allows
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recognition of queries by involved agents. It should include
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the subsystem doing the query and the specific object the
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query is done for. Example:
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<literal>--id=cryptsetup:/dev/sda5</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--keyname=</option></term>
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<listitem><para>Configure a kernel keyring key name to use as
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cache for the password. If set, then the tool will try to push
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any collected passwords into the kernel keyring of the root
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user, as a key of the specified name. If combined with
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<option>--accept-cached</option>, it will also try to retrieve
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such cached passwords from the key in the kernel keyring
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instead of querying the user right away. By using this option,
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the kernel keyring may be used as effective cache to avoid
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repeatedly asking users for passwords, if there are multiple
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objects that may be unlocked with the same password. The
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cached key will have a timeout of 2.5min set, after which it
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will be purged from the kernel keyring. Note that it is
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possible to cache multiple passwords under the same keyname,
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in which case they will be stored as <constant>NUL</constant>-separated list of
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passwords. Use
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<citerefentry project='die-net'><refentrytitle>keyctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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to access the cached key via the kernel keyring
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directly. Example: <literal>--keyname=cryptsetup</literal></para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--credential=</option></term>
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<listitem><para>Configure a credential to read the password from – if it exists. This may be used in
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conjunction with the <varname>LoadCredential=</varname> and <varname>SetCredential=</varname>
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settings in unit files. See
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
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details. If not specified, defaults to <literal>password</literal>. This option has no effect if no
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credentials directory is passed to the program (i.e. <varname>$CREDENTIALS_DIRECTORY</varname> is not
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set) or if the no credential of the specified name exists.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--timeout=</option></term>
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<listitem><para>Specify the query timeout in seconds. Defaults
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to 90s. A timeout of 0 waits indefinitely. </para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--echo=yes|no|masked</option></term>
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<listitem><para>Controls whether to echo user input. Takes a boolean or the special string
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<literal>masked</literal>, the default being the latter. If enabled the typed characters are echoed
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literally, which is useful for prompting for usernames and other non-protected data. If disabled the
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typed characters are not echoed in any form, the user will not get feedback on their input. If set to
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<literal>masked</literal>, an asterisk (<literal>*</literal>) is echoed for each character
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typed. In this mode, if the user hits the tabulator key (<literal>↹</literal>), echo is turned
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off. (Alternatively, if the user hits the backspace key (<literal>⌫</literal>) while no data has
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been entered otherwise, echo is turned off, too).</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--echo</option></term>
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<term><option>-e</option></term>
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<listitem><para>Equivalent to <option>--echo=yes</option>, see above.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--emoji=yes|no|auto</option></term>
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<listitem><para>Controls whether or not to prefix the query with a
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lock and key emoji (🔐), if the TTY settings permit this. The default
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is <literal>auto</literal>, which defaults to <literal>yes</literal>,
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unless <option>--echo=yes</option> is given.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--no-tty</option></term>
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<listitem><para>Never ask for password on current TTY even if
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one is available. Always use agent system.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--accept-cached</option></term>
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<listitem><para>If passed, accept cached passwords, i.e.
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passwords previously entered.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--multiple</option></term>
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<listitem><para>When used in conjunction with
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<option>--accept-cached</option> accept multiple passwords.
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This will output one password per line.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--no-output</option></term>
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<listitem><para>Do not print passwords to standard output. This is useful if you want to store a
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password in kernel keyring with <option>--keyname=</option> but do not want it to show up on screen
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or in logs.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-n</option></term>
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<listitem><para>By default, when writing the acquired password to standard output it is suffixed by a
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newline character. This may be turned off with the <option>-n</option> switch, similar to the switch
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of the same name of the <citerefentry
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project='man-pages'><refentrytitle>echo</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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command.</para></listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="help" />
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Exit status</title>
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<para>On success, 0 is returned, a non-zero failure code
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otherwise.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-ask-password-console.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-tty-ask-password-agent</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry project='die-net'><refentrytitle>keyctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>wall</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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