man/systemd-ask-password.xml

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  10   Copyright 2011 Lennart Poettering
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  25
  26 <refentry id="systemd-ask-password"
  27     xmlns:xi="http://www.w3.org/2001/XInclude">
  28
  29   <refentryinfo>
  30     <title>systemd-ask-password</title>
  31     <productname>systemd</productname>
  32
  33     <authorgroup>
  34       <author>
  35         <contrib>Developer</contrib>
  36         <firstname>Lennart</firstname>
  37         <surname>Poettering</surname>
  38         <email>lennart@poettering.net</email>
  39       </author>
  40     </authorgroup>
  41   </refentryinfo>
  42
  43   <refmeta>
  44     <refentrytitle>systemd-ask-password</refentrytitle>
  45     <manvolnum>1</manvolnum>
  46   </refmeta>
  47
  48   <refnamediv>
  49     <refname>systemd-ask-password</refname>
  50     <refpurpose>Query the user for a system password</refpurpose>
  51   </refnamediv>
  52
  53   <refsynopsisdiv>
  54     <cmdsynopsis>
  55       <command>systemd-ask-password <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt">MESSAGE</arg></command>
  56     </cmdsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para><command>systemd-ask-password</command> may be used to query
  63     a system password or passphrase from the user, using a question
  64     message specified on the command line. When run from a TTY it will
  65     query a password on the TTY and print it to standard output. When
  66     run with no TTY or with <option>--no-tty</option> it will use the
  67     system-wide query mechanism, which allows active users to respond via
  68     several agents, listed below.</para>
  69
  70     <para>The purpose of this tool is to query system-wide passwords
  71     — that is passwords not attached to a specific user account.
  72     Examples include: unlocking encrypted hard disks when they are
  73     plugged in or at boot, entering an SSL certificate passphrase for
  74     web and VPN servers.</para>
  75
  76     <para>Existing agents are:
  77     <itemizedlist>
  78
  79       <listitem><para>A boot-time password agent asking the user for
  80       passwords using
  81       <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  82       </para></listitem>
  83
  84       <listitem><para>A boot-time password agent querying the user
  85       directly on the console —
  86       <citerefentry><refentrytitle>systemd-ask-password-console.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  87       </para></listitem>
  88
  89       <listitem><para>An agent requesting password input via a
  90       <citerefentry project='man-pages'><refentrytitle>wall</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  91       message —
  92       <citerefentry><refentrytitle>systemd-ask-password-wall.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  93       </para></listitem>
  94
  95       <listitem><para>A TTY agent that is temporarily spawned during
  96       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  97       invocations,</para></listitem>
  98
  99       <listitem><para>A command line agent which can be started
 100       temporarily to process queued password
 101       requests — <command>systemd-tty-ask-password-agent --query</command>.
 102       </para></listitem>
 103     </itemizedlist></para>
 104
 105     <para>Answering system-wide password queries is a privileged operation, hence
 106     all the agents listed above (except for the last one), run as privileged
 107     system services. The last one also needs elevated privileges, so
 108     should be run through
 109     <citerefentry project='die-net'><refentrytitle>sudo</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 110     or similar.</para>
 111
 112     <para>Additional password agents may be implemented according to
 113     the <ulink
 114     url="https://www.freedesktop.org/wiki/Software/systemd/PasswordAgents">systemd
 115     Password Agent Specification</ulink>.</para>
 116
 117     <para>If a password is queried on a TTY, the user may press TAB to
 118     hide the asterisks normally shown for each character typed.
 119     Pressing Backspace as first key achieves the same effect.</para>
 120
 121   </refsect1>
 122
 123   <refsect1>
 124     <title>Options</title>
 125
 126     <para>The following options are understood:</para>
 127
 128     <variablelist>
 129       <varlistentry>
 130         <term><option>--icon=</option></term>
 131
 132         <listitem><para>Specify an icon name alongside the password
 133         query, which may be used in all agents supporting graphical
 134         display. The icon name should follow the <ulink
 135         url="http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html">XDG
 136         Icon Naming Specification</ulink>.</para></listitem>
 137       </varlistentry>
 138
 139       <varlistentry>
 140         <term><option>--id=</option></term>
 141         <listitem><para>Specify an identifier for this password
 142         query. This identifier is freely choosable and allows
 143         recognition of queries by involved agents. It should include
 144         the subsystem doing the query and the specific object the
 145         query is done for. Example:
 146         <literal>--id=cryptsetup:/dev/sda5</literal>.</para></listitem>
 147       </varlistentry>
 148
 149       <varlistentry>
 150         <term><option>--keyname=</option></term>
 151         <listitem><para>Configure a kernel keyring key name to use as
 152         cache for the password. If set, then the tool will try to push
 153         any collected passwords into the kernel keyring of the root
 154         user, as a key of the specified name. If combined with
 155         <option>--accept-cached</option>, it will also try to retrieve
 156         such cached passwords from the key in the kernel keyring
 157         instead of querying the user right away. By using this option,
 158         the kernel keyring may be used as effective cache to avoid
 159         repeatedly asking users for passwords, if there are multiple
 160         objects that may be unlocked with the same password. The
 161         cached key will have a timeout of 2.5min set, after which it
 162         will be purged from the kernel keyring. Note that it is
 163         possible to cache multiple passwords under the same keyname,
 164         in which case they will be stored as NUL-separated list of
 165         passwords. Use
 166         <citerefentry project='die-net'><refentrytitle>keyctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 167         to access the cached key via the kernel keyring
 168         directly. Example: <literal>--keyname=cryptsetup</literal></para></listitem>
 169       </varlistentry>
 170
 171       <varlistentry>
 172         <term><option>--timeout=</option></term>
 173
 174         <listitem><para>Specify the query timeout in seconds. Defaults
 175         to 90s. A timeout of 0 waits indefinitely. </para></listitem>
 176       </varlistentry>
 177
 178       <varlistentry>
 179         <term><option>--echo</option></term>
 180
 181         <listitem><para>Echo the user input instead of masking it.
 182         This is useful when using
 183         <filename>systemd-ask-password</filename> to query for
 184         usernames. </para></listitem>
 185       </varlistentry>
 186
 187       <varlistentry>
 188         <term><option>--no-tty</option></term>
 189
 190         <listitem><para>Never ask for password on current TTY even if
 191         one is available. Always use agent system.</para></listitem>
 192       </varlistentry>
 193
 194       <varlistentry>
 195         <term><option>--accept-cached</option></term>
 196
 197         <listitem><para>If passed, accept cached passwords, i.e.
 198         passwords previously entered.</para></listitem>
 199       </varlistentry>
 200
 201       <varlistentry>
 202         <term><option>--multiple</option></term>
 203
 204         <listitem><para>When used in conjunction with
 205         <option>--accept-cached</option> accept multiple passwords.
 206         This will output one password per line.</para></listitem>
 207       </varlistentry>
 208
 209       <varlistentry>
 210         <term><option>--no-output</option></term>
 211
 212         <listitem><para>Do not print passwords to standard output.
 213         This is useful if you want to store a password in kernel
 214         keyring with <option>--keyname</option> but do not want it
 215         to show up on screen or in logs.</para></listitem>
 216       </varlistentry>
 217
 218       <xi:include href="standard-options.xml" xpointer="help" />
 219     </variablelist>
 220
 221   </refsect1>
 222
 223   <refsect1>
 224     <title>Exit status</title>
 225
 226     <para>On success, 0 is returned, a non-zero failure code
 227     otherwise.</para>
 228   </refsect1>
 229
 230   <refsect1>
 231     <title>See Also</title>
 232     <para>
 233       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 234       <citerefentry><refentrytitle>systemd-ask-password-console.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 235       <citerefentry><refentrytitle>systemd-tty-ask-password-agent</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 236       <citerefentry project='die-net'><refentrytitle>keyctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 237       <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 238       <citerefentry project='man-pages'><refentrytitle>wall</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 239     </para>
 240   </refsect1>
 241
 242 </refentry>