systemd-ask-password — Query the user for a system password
systemd-ask-password [OPTIONS...] [MESSAGE]
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.
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.
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.
--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"
--timeout=¶Specify the query timeout in seconds. Defaults to 90s. A timeout of 0 waits indefinitely.
--echo¶Echo the user input instead of masking it.
This is useful when using
systemd-ask-password to query for
usernames.
--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.
-h, --help¶