mirror of
https://github.com/morgan9e/systemd
synced 2026-04-14 00:14:32 +09:00
b7ba8d55b8
When services start up they might query for passwords, or issue polkit
requests. Hence it makese sense to run the password query agent and
polkit agent from systemd-run. We already ran the polkit agent, this
also ensures we run the password query agent.
There's one tweak to the story though: running the agents and the pty
forwarder concurrently is messy, since they both try to read from stdin
(one potentially, the other definitely). Hence, let's time the agents
properly: invoke them when we initialize, but stop them once the start
job for the unit we are supposed to run is complete, and only then run
the pty forwarder.
With this in place, the following series of commands starts to work
really nicely (which previously deadlocked):
# homectl create foobar
# run0 -u foobar
What happens in the background in run0 is this: a new session is invoked
for "foobar", which pulls in the user@.service instance for the user.
That user@.service instance will need to unlock the homedir first. Since
8af1b296cb this will happen via the askpw
logic. With this commit here this prompt will now be shown by run0. Once
the password is entered the directory is unlocked and the real session
begins. Nice!
This new behaviour is conditioned behind --pty-late (distinct from the
existing --pty switches). For systemd-run we will never enable this mode
by default, for compat with command lines that use ExecStartPre=
(because we won't process the pty anymore during that command) For
run0 however this changes the default to --pty-late (unless
--no-ask-password is specified). This reflects the fact that run0 is
more of an interctive tool and unlikely to be used in more complex
service start-up situations with ExecStartPre= and suchlike.
This also merges JobDoneContext into RunContext, since it doesn't really
make sense to have two contexts around to communicate between outer
stack frame and event handlers. Let's just have one, and pass it around
to all handlers the same way. In particular as we should delay exit only
until both the unit's job is complete *and* in case of --wait the unit
is exited, one of the two should not suffice.
378 lines
17 KiB
XML
378 lines
17 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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<refentry id="run0"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>run0</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>run0</refentrytitle>
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<manvolnum>1</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>run0</refname>
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<refpurpose>Elevate privileges</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>run0</command>
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<arg choice="opt" rep="repeat">OPTIONS</arg>
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<arg choice="opt" rep="repeat">COMMAND</arg>
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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>run0</command> may be used to temporarily and interactively acquire elevated or different
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privileges. It serves a similar purpose as <citerefentry
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project='man-pages'><refentrytitle>sudo</refentrytitle><manvolnum>8</manvolnum></citerefentry>, but
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operates differently in a couple of key areas:</para>
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<itemizedlist>
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<listitem><para>No execution or security context credentials are inherited from the caller into the
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invoked commands, as they are invoked from a fresh, isolated service forked off by the service manager.
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</para></listitem>
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<listitem><para>Authentication takes place via <ulink
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url="https://www.freedesktop.org/wiki/Software/polkit">polkit</ulink>, thus isolating the
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authentication prompt from the terminal (if possible).</para></listitem>
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<listitem><para>An independent pseudo-tty is allocated for the invoked command, detaching its lifecycle and
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isolating it for security.</para></listitem>
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<listitem><para>No SetUID/SetGID file access bit functionality is used for the implementation.</para></listitem>
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</itemizedlist>
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<para>Altogether this should provide a safer and more robust alternative to the <command>sudo</command>
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mechanism, in particular in OS environments where SetUID/SetGID support is not available (for example by
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setting the <varname>NoNewPrivileges=</varname> variable in
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<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
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<para>Any session invoked via <command>run0</command> will run through the
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<literal>systemd-run0</literal> PAM stack.</para>
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<para>Note that <command>run0</command> is implemented as an alternative multi-call invocation of
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<citerefentry><refentrytitle>systemd-run</refentrytitle><manvolnum>1</manvolnum></citerefentry>. That is,
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<command>run0</command> is a symbolic link to <command>systemd-run</command> executable file, and it
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behaves as <command>run0</command> if it is invoked through the symbolic link, otherwise behaves as
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<command>systemd-run</command>.</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>--unit=</option></term>
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<listitem><para>Use this unit name instead of an automatically generated one.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--property=</option></term>
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<listitem><para>Sets a property of the service unit that is created. This option takes an assignment
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in the same format as
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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<command>set-property</command> command.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--description=</option></term>
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<listitem><para>Provide a description for the service unit that is invoked. If not specified,
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the command itself will be used as a description. See <varname>Description=</varname> in
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
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</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--slice=</option></term>
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<listitem><para>Make the new <filename>.service</filename> unit part of the specified slice, instead
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of <filename>user.slice</filename>.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--slice-inherit</option></term>
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<listitem><para>Make the new <filename>.service</filename> unit part of the slice the
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<command>run0</command> itself has been invoked in. This option may be combined with
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<option>--slice=</option>, in which case the slice specified via <option>--slice=</option> is placed
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within the slice the <command>run0</command> command is invoked in.</para>
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<para>Example: consider <command>run0</command> being invoked in the slice
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<filename>foo.slice</filename>, and the <option>--slice=</option> argument is
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<filename>bar</filename>. The unit will then be placed under
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<filename>foo-bar.slice</filename>.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--user=</option></term>
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<term><option>-u</option></term>
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<term><option>--group=</option></term>
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<term><option>-g</option></term>
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<listitem><para>Switches to the specified user/group. If not specified defaults to
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<literal>root</literal>, unless <option>--area=</option> is used (see below), in which case this
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defaults to the invoking user.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--nice=</option></term>
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<listitem><para>Runs the invoked session with the specified nice level.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--chdir=</option></term>
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<term><option>-D</option></term>
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<listitem><para>Runs the invoked session with the specified working directory. If not specified
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defaults to the client's current working directory if switching to the root user, or the target
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user's home directory otherwise.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--setenv=<replaceable>NAME</replaceable>[=<replaceable>VALUE</replaceable>]</option></term>
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<listitem><para>Runs the invoked session with the specified environment variable set. This parameter
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may be used more than once to set multiple variables. When <literal>=</literal> and
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<replaceable>VALUE</replaceable> are omitted, the value of the variable with the same name in the
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invoking environment will be used.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--background=<replaceable>COLOR</replaceable></option></term>
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<listitem><para>Change the terminal background color to the specified ANSI color as long as the
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session lasts. If not specified, the background will be tinted in a reddish tone when operating as
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root, and in a yellowish tone when operating under another UID, as reminder of the changed
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privileges. The color specified should be an ANSI X3.64 SGR background color, i.e. strings such as
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<literal>40</literal>, <literal>41</literal>, …, <literal>47</literal>, <literal>48;2;…</literal>,
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<literal>48;5;…</literal>. See <ulink
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url="https://en.wikipedia.org/wiki/ANSI_escape_code#SGR_(Select_Graphic_Rendition)_parameters">ANSI
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Escape Code (Wikipedia)</ulink> for details. Set to an empty string to disable.</para>
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<para>Example: <literal>--background=44</literal> for a blue background.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--pty</option></term>
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<term><option>--pty-late</option></term>
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<term><option>--pipe</option></term>
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<listitem><para>Request allocation of a pseudo TTY for the <command>run0</command> session (in case
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of <option>--pty</option> or <option>--pty-late</option>), or request passing the caller's STDIO file
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descriptors directly through (in case of <option>--pipe</option>). <option>--pty-late</option> is
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very similar to <option>--pty</option> but begins the TTY processing only once unit startup is
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complete, leaving input to any passwords/polkit agents until that time. If neither switch is
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specified, or if both <option>--pipe</option> and one of
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<option>--pty</option>/<option>--pty-late</option> are specified, the mode will be picked
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automatically: if standard input, standard output, and standard error output are all connected to a
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TTY then a pseudo TTY is allocated (in <option>--pty-late</option> mode unless
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<option>--no-ask-password</option> is specified in which case <option>--pty</option> is selected),
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otherwise the relevant file descriptors are passed through directly.</para>
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<para id="v257"><option>--pty</option> and <option>--pipe</option> were added in v257.</para>
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<para id="v258"><option>--pty-late</option> was added in v258.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--shell-prompt-prefix=<replaceable>STRING</replaceable></option></term>
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<listitem><para>Set a shell prompt prefix string. This ultimately controls the
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<varname>$SHELL_PROMPT_PREFIX</varname> environment variable for the invoked program, which is
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typically imported into the shell prompt. By default – if emojis are supported –, a superhero emoji is
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shown (🦸). This default may also be changed (or turned off) by passing the
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<varname>$SYSTEMD_RUN_SHELL_PROMPT_PREFIX</varname> environment variable to <varname>run0</varname>,
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see below. Set to an empty string to disable shell prompt prefixing.</para>
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<xi:include href="version-info.xml" xpointer="v257"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--lightweight=<replaceable>BOOLEAN</replaceable></option></term>
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<listitem><para>Controls whether to activate the per-user service manager for the target user. By
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default if the target user is <literal>root</literal> or a system user the per-user service manager
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is not activated as effect of the <command>run0</command> invocation, otherwise it is.</para>
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<para>This ultimately controls the <varname>$XDG_SESSION_CLASS</varname> environment variable
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<citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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respects.</para>
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<xi:include href="version-info.xml" xpointer="v258"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-a <replaceable>AREA</replaceable></option></term>
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<term><option>--area=<replaceable>AREA</replaceable></option></term>
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<listitem><para>Controls the "area" of the target account to log into. Areas are secondary home
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directories within the primary home directory of the target user, i.e. logging into area
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<literal>foobar</literal> of an account translates to <varname>$HOME</varname> being set to
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<filename>~/Areas/foobar</filename> on login.</para>
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<para>If this option is used, the default user to transition to changes from root to the calling
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user's (but <option>--user=</option> takes precedence, see above). Or in other words, just specifying
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an area without a user is a mechanism to create a new session of the calling user, just with a
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different area.</para>
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<para>This ultimately controls the <varname>$XDG_AREA</varname> environment variable
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<citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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respects.</para>
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<para>For details on the area concept see
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<citerefentry><refentrytitle>pam_systemd_home</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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<xi:include href="version-info.xml" xpointer="v258"/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--machine=</option></term>
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<listitem>
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<para>Execute operation in a local container. Specify a container name to connect to.</para>
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<xi:include href="version-info.xml" xpointer="v256"/>
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</listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="no-ask-password" />
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<xi:include href="standard-options.xml" xpointer="help" />
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<xi:include href="standard-options.xml" xpointer="version" />
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</variablelist>
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<para>All command line arguments after the first non-option argument become part of the command line of
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the launched process. If no command line is specified an interactive shell is invoked. The shell to
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invoke may be controlled via <option>--setenv=SHELL=…</option> and currently defaults to the
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<emphasis>originating user's</emphasis> shell (i.e. not the target user's!) if operating locally, or
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<filename>/bin/sh</filename> when operating with <option>--machine=</option>.</para>
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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. If <command>run0</command> failed to start the session or the specified command fails, a
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non-zero return value will be returned.</para>
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</refsect1>
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<refsect1>
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<title>Environment Variables</title>
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<para>As with <command>systemd-run</command>, the session will inherit the system
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environment from the service manager. In addition, the following environment variables will be set:</para>
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<variablelist>
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<varlistentry>
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<term><varname>$TERM</varname></term>
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<listitem><para>Copied from the <varname>$TERM</varname> of the caller. Can be overridden with
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<option>--setenv=</option></para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$SUDO_USER</varname></term>
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<listitem><para>Set to the username of the originating user.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$SUDO_UID</varname></term>
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<listitem><para>Set to the numeric UNIX user id of the originating user.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$SUDO_GID</varname></term>
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<listitem><para>Set to the primary numeric UNIX group id of the originating session.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$SHELL_PROMPT_PREFIX</varname></term>
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<listitem><para>By default, set to the superhero emoji (if supported), but may be overridden with the
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<varname>$SYSTEMD_RUN_SHELL_PROMPT_PREFIX</varname> environment variable (see below), or the
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<option>--shell-prompt-prefix=</option> switch (see above).</para>
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<xi:include href="version-info.xml" xpointer="v257"/></listitem>
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</varlistentry>
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</variablelist>
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<para>The following variables may be passed to <command>run0</command>:</para>
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<variablelist>
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<varlistentry>
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<term><varname>$SYSTEMD_RUN_SHELL_PROMPT_PREFIX</varname></term>
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<listitem><para>If set, overrides the default shell prompt prefix that <command>run0</command> sets
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for the invoked shell (the superhero emoji). Set to an empty string to disable shell prompt
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prefixing.</para>
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<xi:include href="version-info.xml" xpointer="v257"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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||
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-run</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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||
<member><citerefentry project='man-pages'><refentrytitle>sudo</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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||
<member><citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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