serial console and log-in

[Denis Vlasenko]

On Tuesday 06 March 2007 14:00, Natanael Copa wrote:
> > How about writing small hack which analyzes stdin (fd #0)
> > and closes fd #0,1,2 + reopens/dups /dev/ttyN or /dev/ttySn:
...
> > Use it like this:
> > 
> > ::respawn:/somewhere/cttyhack /sbin/getty - 9600 vt100
> > 
> > Care to try? ;)
> 
> I tried this. This works. Does the job.

Yes, I also tried it for bug hunting session. If more people
will find it useful, maybe we should have it then.

> However, its is hackish as you 
> said:
> 
> ~ $ who
> USER       TTY      IDLE      TIME           HOST
> root       -        ?         Mar  6 12:39   
> root       tty2     .         Mar  6 12:48   
>
> Note that TTY ends up as -
> Are there any drawback with this? Can this make other programs behave
> strange?

Our who searches for TTY in utmp, and our getty, if run with '-',
places '-' in utmp as login console name.

IOW: it is mostly cosmetic and shouldn't affect anything.

> Another hackish way to solve it would be to have a 'is_serial_tty'
> binary in the initramfs:
> 
> /* is_serial_tty.c */
> int main() {
>         return (ioctl(0, TIOCGSERIAL, &sr) != 0);
> }
> 
> and then copy a second inittab to new root, before running switchroot.
>
> This is also hackish and I don't know whats worst.

It will not work if console is somehow placed on ttyS1 - your
"serial" inittab will probably expect ttyS0.
 
> I'm seriously thinking of writing a new init, based on the upstart
> ideas. (unlike runinit, it will reuse sysv init.d scripts)

<subliminal message>

http://busybox.net/~vda/example_fs/README

</subliminal message>
--
vda
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