This package contains tools for running and managing TUI login services on both kernel and user-space virtual terminals. It also contains pre-written service bundles for such TUI login services.
runscripts look like
run scripts are interpreted by
nosh and are created from a template with the terminal name hardwired.
run script to provide TUI login on kernel virtual terminal
/dev/ttyv4 would be something like this:
#!/bin/nosh setsid vc-get-tty ttyv4 open-controlling-tty vc-reset-tty login-banner /etc/issue.vc login
run script for a service to provide TUI login on user-space virtual terminal
/run/dev/vc1 would be something like:
#!/bin/nosh setsid vc-get-tty vc1/tty open-controlling-tty vc-reset-tty login-banner /etc/issue.vc login
run scripts for these services use the chain loading tools to do what one would otherwise do with
They are even more minimal than "minimal
getty" is, and cut out much of the functionality of a full
getty that is either invariant or non-existent on virtual terminals.
Several parts of this are specialized, hardwiring things that are variable in general, but that are in fact invariant for virtual terminals.
Serial-line getty programs like
agetty deal in things like modem connect strings, serial line speeds, modem flow control, parity, dial-out interlocks, and suchlike.
None of those things apply to virtual terminals; and the tools are simpler for having no dealings with them.
As their names suggest,
vc-reset-tty are specialized tools for virtual terminals; those are what they are designed for and what they primarily target.
Both the terminal types set by the former and the control sequences emitted by the latter are fixed and determined by the user-space terminal emulator or the terminal emulator in the operating system kernel, and won't change in the way that real terminals attached to serial lines can.
login-banner /etc/issue login is a common sequence for login services.
run scripts are recomposable and this chain is an example of that.
One can adjust the behaviour of the service to suit particular needs by altering the tool chain or particular tool options.
login programs employ an idle timeout feature, whereby they exit if login has not completed within a set period of time, such as 60 seconds.
Terminal login as a proper service, managed by a service manager, operates suboptimally if the service is continually exiting, because
login has timed out, every 60 seconds.
At the very least, it is annoying chaff in the service logs.
One way to fix this is to remove the timeout from
login's configuration file, whatever that may be, of course.
Another is to put
login-prompt into the chain:
login-prompt login-banner /etc/issue login
login-prompt run first ensures that the service does not keep timing out and exiting.
The prompt that it displays is of course familiar Unix behaviour, that mimics the behaviour of serial line
getty services on variable-speed lines.
They can require that one press Return several times as the program attempts to guess the correct terminal line speed to set.
login programs handle the creation, and nowadays also the cleanup, of
utmpx database entries for successful logins.
On BSDs the notion of
utmpx records for anything other than the logged-in state of a terminal never existed in the first place.
Linux still retains the System 5 notion of terminals that are in the "init" and "login" states, even though they no longer apply.
(The "init" state has no meaning for systems where the terminal login service isn't managed by process #1 any more; and as can be seen here there is no real "getty" state for kernel virtual terminals as most of the serial line functions of
getty don't apply.)
To maintain such obsolete records nonetheless, one simply inserts
login-process into the chain:
login-process login-prompt login-banner /etc/issue login
On Linux and BSDs, kernel virtual terminals may retain terminal state from previous logins that affects the viewability of subsequent logins.
Existing processes can also end up retaining open file descriptors for the terminal device.
To forcibly reset a virtual console, using mechanisms that are specific to kernel virtual consoles, one can employ the
--text-mode and other options to
vc-reset-tty; and to forcibly remove access to open file descriptors one can employ the
--revoke options to
There are some differences between user-space and kernel virtual terminals that simplify such scripts yet further:
User-space virtual terminals are created afresh (a new pseudo-terminal back end and front end pair) at service start, so there is no need for the
--vhangup option to
User-space virtual terminals are initialized into a sane state (both the line discipline and the terminal emulator's attributes, colours, and character repertoire) at start, so there is no need for the
--hard-reset option to
User-space virtual terminals do not have a graphics mode, so there is no need for the
--text-mode option to