Parece que una contraseña vacía no coincide con los requisitos de Complejidad de contraseña.
Esto es lo que encontré en man passwd
As a general guideline, passwords should consist of 6 to 8 characters including one or
more characters from each of the following sets:
· lower case alphabetics
· digits 0 thru 9
· punctuation marks
Care must be taken not to include the system default erase or kill characters. passwd will reject any password which is not
suitably complex.
EDITAR: Desafortunadamente, no puede configurar la contraseña para que se vacíe a través de esa interfaz de usuario.
http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/quantal/gnome-control-center/quantal-proposed/view/head:/panels/user-accounts/um-password-dialog.c#L358
es la función que decide si habilitar el botón "Cambiar" o no.
if (strlen (password) < MIN_PASSWORD_LEN) {
can_change = FALSE;
if (password[0] == '\0') {
tooltip = _("You need to enter a new password");
}
else {
tooltip = _("The new password is too short");
}
}
else if (strcmp (password, verify) != 0) {
can_change = FALSE;
if (verify[0] == '\0') {
tooltip = _("You need to confirm the password");
}
else {
tooltip = _("The passwords do not match");
}
}
else if (!um->old_password_ok) {
can_change = FALSE;
if (old_password[0] == '\0') {
tooltip = _("You need to enter your current password");
}
else {
tooltip = _("The current password is not correct");
}
}
else {
can_change = TRUE;
tooltip = NULL;
}
gtk_widget_set_sensitive (um->ok_button, can_change);
La contraseña mínima len 6 está codificada :(
http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/quantal/gnome-control-center/quantal-proposed/view/head:/panels/user-accounts/um-password-dialog.c#L39
#define MIN_PASSWORD_LEN 6
pkexec
, consulte askubuntu.com/a/614537/158442