Ubuntu Manpage: systemd-ask-password - Query the user for a system password

Provided by: systemd_253.5-1ubuntu6.1_amd64

NAME

       systemd-ask-password - Query the user for a system password

SYNOPSIS

       systemd-ask-password [OPTIONS...] [MESSAGE]

DESCRIPTION

systemd-ask-password may be used to query a system password or passphrase from the user,
using a question message specified on the command line. When run from a TTY it will query
a password on the TTY and print it to standard output. When run with no TTY or with
--no-tty it will use the system-wide query mechanism, which allows active users to respond
via several agents, listed below.

The purpose of this tool is to query system-wide passwords — that is passwords not
attached to a specific user account. Examples include: unlocking encrypted hard disks when
they are plugged in or at boot, entering an SSL certificate passphrase for web and VPN
servers.

Existing agents are:

• A boot-time password agent asking the user for passwords using plymouth(8),

• A boot-time password agent querying the user directly on the console — systemd-ask-
password-console.service(8),

• An agent requesting password input via a wall(1) message — systemd-ask-password-
wall.service(8),

• A TTY agent that is temporarily spawned during systemctl(1) invocations,

• A command line agent which can be started temporarily to process queued password
requests — systemd-tty-ask-password-agent --query.

Answering system-wide password queries is a privileged operation, hence all the agents
listed above (except for the last one), run as privileged system services. The last one
also needs elevated privileges, so should be run through sudo(8) or similar.

Additional password agents may be implemented according to the systemd Password Agent
Specification[1].

If a password is queried on a TTY, the user may press TAB to hide the asterisks normally
shown for each character typed. Pressing Backspace as first key achieves the same effect.

OPTIONS

The following options are understood:

--icon=
Specify an icon name alongside the password query, which may be used in all agents
supporting graphical display. The icon name should follow the XDG Icon Naming
Specification[2].

--id=
Specify an identifier for this password query. This identifier is freely choosable and
allows recognition of queries by involved agents. It should include the subsystem
doing the query and the specific object the query is done for. Example:
"--id=cryptsetup:/dev/sda5".

--keyname=
Configure a kernel keyring key name to use as cache for the password. If set, then the
tool will try to push any collected passwords into the kernel keyring of the root
user, as a key of the specified name. If combined with --accept-cached, it will also
try to retrieve such cached passwords from the key in the kernel keyring instead of
querying the user right away. By using this option, the kernel keyring may be used as
effective cache to avoid repeatedly asking users for passwords, if there are multiple
objects that may be unlocked with the same password. The cached key will have a
timeout of 2.5min set, after which it will be purged from the kernel keyring. Note
that it is possible to cache multiple passwords under the same keyname, in which case
they will be stored as NUL-separated list of passwords. Use keyctl(1) to access the
cached key via the kernel keyring directly. Example: "--keyname=cryptsetup"

--credential=
Configure a credential to read the password from – if it exists. This may be used in
conjunction with the LoadCredential= and SetCredential= settings in unit files. See
systemd.exec(5) for details. If not specified, defaults to "password". This option has
no effect if no credentials directory is passed to the program (i.e.
$CREDENTIALS_DIRECTORY is not set) or if the no credential of the specified name
exists.

--timeout=
Specify the query timeout in seconds. Defaults to 90s. A timeout of 0 waits
indefinitely.

--echo=yes|no|masked
Controls whether to echo user input. Takes a boolean or the special string "masked",
the default being the latter. If enabled the typed characters are echoed literally,
which is useful for prompting for usernames and other non-protected data. If disabled
the typed characters are not echoed in any form, the user will not get feedback on
their input. If set to "masked", an asterisk ("*") is echoed for each character typed.
In this mode, if the user hits the tabulator key ("↹"), echo is turned off.
(Alternatively, if the user hits the backspace key ("⌫") while no data has been
entered otherwise, echo is turned off, too).

--echo, -e
Equivalent to --echo=yes, see above.

--emoji=yes|no|auto
Controls whether or not to prefix the query with a lock and key emoji (🔐), if the TTY
settings permit this. The default is "auto", which defaults to "yes", unless
--echo=yes is given.

--no-tty
Never ask for password on current TTY even if one is available. Always use agent
system.

--accept-cached
If passed, accept cached passwords, i.e. passwords previously entered.

--multiple
When used in conjunction with --accept-cached accept multiple passwords. This will
output one password per line.

--no-output
Do not print passwords to standard output. This is useful if you want to store a
password in kernel keyring with --keyname= but do not want it to show up on screen or
in logs.

-n
By default, when the acquired password is written to standard output it is suffixed by
a newline character. This may be turned off with the -n switch, similarly to the
switch of the same name of the echo(1) command.

-h, --help
Print a short help text and exit.

EXIT STATUS

       On success, 0 is returned, a non-zero failure code otherwise.

NOTES