iNode: Nota Bene

My good speakers are hooked up to an old server machine, which presents through a nice small 15" LCD monitor on the desk.

The server doesn't run a GUI of course, so I do music playback from the commandline with programs like mpg123 and mp3blaster.

I decided to dedicate the first text console to playback, so I needed to replace the login prompt with the mp3blaster program. I hadn't noticed that Ubuntu no longer has an /etc/inittab file, because it has switched to the more flexible Upstart system, so it took a few minuted to find out how to get this set up.

Hacking on Upstart

The first port of call is the /etc/event.d/tty1 file, which by default is running getty for us. I'm keeping getty (although other tty programs are out there and may do the job in a nicer way), so I need to ask it to run different “login” program, using the -n and -l options. Just for luck, I also set the TERM type explicitly.

getty doesn't like to send arguments to the login program, so I had to set up a small script to do the hard work. Make sure that the filesystem this script lives in is available when Upstart is started … however I suspect that Upstart is actually smart enough to figure this out :-)

/etc/event.d/tty1

# tty1 - getty
#
# This service maintains a getty on tty1 from the point the system is
# started until it is shut down again.

start on stopped rc2
start on stopped rc3
start on stopped rc4
start on stopped rc5

stop on runlevel 0
stop on runlevel 1
stop on runlevel 6

respawn
#exec /sbin/getty 38400 tty1
exec /sbin/getty -n -l /usr/local/bin/jimp3 38400 tty1 linux

Next, the helper script; I need to invoke mp3blaster autostarting a playlist, but I also want it to run as my user, rather than root. Good old su is a simple way of achieving this.

/usr/local/bin/jimp3

#!/bin/sh
/bin/su -c '/usr/bin/mp3blaster -a /home/jim/allmusic.lst' -- jim

Do NOT reboot!

No need to reboot the server to get this all running! Use the initctl command to find the ‘tty1’ job that is currently running a login shell, stop it and then restart it.

# initctl list
control-alt-delete (stop) waiting
logd (stop) waiting
rc-default (stop) waiting
rc0 (stop) waiting
rc1 (stop) waiting
rc2 (stop) waiting
rc3 (stop) waiting
rc4 (stop) waiting
rc5 (stop) waiting
rc6 (stop) waiting
rcS (stop) waiting
rcS-sulogin (stop) waiting
sulogin (stop) waiting
tty1 (start) running, process 5622
tty2 (start) running, process 4235
tty3 (start) running, process 4236
tty4 (start) running, process 4230
tty5 (start) running, process 4231
tty6 (start) running, process 4238

# initctl stop tty1
tty1 (stop) running, process 5622
tty1 (stop) pre-stop, (main) process 5622
tty1 (stop) stopping, process 5622
tty1 (stop) killed, process 5622
tty1 (stop) post-stop
tty1 (stop) waiting

# initctl start tty1
tty1 (start) waiting
tty1 (start) starting
tty1 (start) pre-start
tty1 (start) spawned, process 6469
tty1 (start) post-start, (main) process 6469
tty1 (start) running, process 6469

Job done! You should now have a copy of mp3blaster running on the first virtual console, playing your playlist for you, as your userid … and if you quit the program, it'll restart straight away.

Tim Elverston's latest kite appeals to the computer geek …

http://www.windfiredesigns.com/timbofolio_pages/PointerKite.html

He promises more to come in the OS series of kites …. probably Windows :-(