source: server/README.old @ 30beeab

gutenbach
    The SIPB MP3 Music Spooler

We would love you forever if you took this README/INSTALL document and made
a Debian package out of it.  That would be uber-awesome.  But otherwise, we're
assuming that you just want to get gutenbach up and running on your own
system.  Well, maybe we shouldn't assume that.


What does gutenbach do?
---------------------

gutenbach is a music spooler.  As it turns out, streaming music is a hard
problem, with lots of proprietary protocols, client and server software.
All of these jiggety bits are kind of a pain to get working correctly,
so, we built gutenbach on top of... a printer system.  It's very simple:
you print an mp3 file to a special "printer", and it gets played on
whatever speakers you're hooked up to.


Prerequisites
-------------

You'll need a server hooked up to an audio system that you want to use, with
Debathena installed on top of it.  Ubuntu Server Edition tends to work
well.


Installing gutenbach
------------------


1. Configuring your sound

If you're installing gutenbach on a server environment, it's highly likely
that you have a bare bones audio setup and everything is muted.  Make sure
your sound works!  One common problem is that the daemon user (the user which
will be actually playing the songs, or the user that your lpd, the print server,
will be running under), isn't in the group audio, and thus can't play
anything. If you're on Ubuntu Desktop, you'll probably have pulse-audio
installed, in which case you should add lpd to the pulse-audio group
as well, and make pulse-audio a single, system-wide instance. See
this URL for detailed instructions:

    http://www.pulseaudio.org/wiki/SystemWideInstance


2. Install some prerequisite software

On a vanilla Ubuntu server install, gutenbach will also need the following
packages to work properly:

    * mplayer
    * libimage-exiftool-perl

mpg123 can also be useful for testing, but is not strictly necessary.


3. Setup gutenbach

The Git repository for gutenbach is located in:

    /afs/sipb/project/sipbmp3/gutenbach.git

Place this in /root/gutenbach; the remctl scripts will assume that the
scripts can be found in this location.


4. Configure gutenbach

gutenbach will send zephyrs during playback start and end.  Since you don't
want to be spamming sipb-auto (which is the default zephyr class these
are sent to), you should create a configuration file:

    /etc/gutenbach-filter-config.pl

That looks like:

    $zephyr_class = "my-auto-class"
    $host = "hostname"
    $queue = "printername"

XXX: Auto-detect hostname and invent a sane default zephyr class off of it.


5. Configure gutenbach init scripts

gutenbach will attempt to drop some information into /var/run/gutenbach, which
needs to exist and you can't simply mkdir since /var/run on Ubuntu is
a tempfs. Thus, add the following lines to a new file, /etc/init.d/gutenbach:

#!/bin/sh
mkdir /var/run/gutenbach
touch /var/run/gutenbach/status
chmod 0777 /var/run/gutenbach/status

You should also run these commands yourself. :-)

XXX: Note from jhamrick: I would recomment actually setting this up as a nice startup script, with a switch case for {start|stop|restart} (where with stop you just remove the directory, and with restart you remove the directory and then recreate it).  Also, gutenbach won't actually run on startup unless there are scripts in the /etc/rc*.d directory, so we need to do:

> ln -s ../init.d/gutenbach /etc/rc2.d/S61gutenbach
> ln -s ../init.d/gutenbach /etc/rc3.d/S61gutenbach
> ln -s ../init.d/gutenbach /etc/rc4.d/S61gutenbach
> ln -s ../init.d/gutenbach /etc/rc5.d/S61gutenbach
> ln -s ../init.d/gutenbach /etc/rc0.d/K39gutenbach
> ln -s ../init.d/gutenbach /etc/rc1.d/K39gutenbach
> ln -s ../init.d/gutenbach /etc/rc6.d/K39gutenbach

XXX: We need better permissions for status. Also, quentin wants to put this
file in AFS.


6. Configure lpd

You'll need to setup a printcap file so that your machine will be actually
running a printer! The magic lines are:

    :if=|/path/to/gutenbach-filter
    :lp=/dev/null

Which mean that we pipe the mp3 files through gutenbach-filter (which does
the actual playing), and then dump the rest of the output into /dev/null,
since we don't actually care about it.

A standard printcap entry looks like this:

printername
  :server
  :cm=Human Readable Printer Name
  :lp=/dev/null
  :if=|/path/to/gutenbach-filter
  :sd=/var/spool/lpd/printername
  :ml=0:mx=0:sh:sf
  :create_files

printcap is located in /etc/printcap, but you can also edit the symlink
in /etc/lprng/printcap.

In /etc/lprng/lpd.conf:

    printcap_path=...

add /etc/lprng/printcap to the beginning of the pathlist, so it looks like:

    printcap_path=/etc/lprng/printcap:|/usr/lib/get_hesiod_pcap

/etc/printcap will also work, assuming lprng doesn't do something funky
in the future.

WARNING: On a cluster machine, get_hesiod_pcap will clobber gutenbach
because it sets all:all=someotherprinter, making lpr not see gutenbach.
There are two ways of fixing this:

1. Patch /usr/lib/get_hesiod_pcap to return a full pcap line instead
of all when it gets "all" from stdin.

2. Remove get_hesiod_pcap from the list.

To check your modifications, and create the necessary files and folders,
you should run:

    checkpc -V -f

(As root, of course). You might get a failure on a directory
/var/spool/lpd/%P doesn't exist; simply mkdir it and run checkpc -V -f

With recent versions of lprng, you will also need to make lpd less paranoid
about accepting connections.  This usually means the following two changes:

In /etc/lprng/lpd.perms:

    REJECT NOT SERVER

should be commented out, as:

    #REJECT NOT SERVER

You will also need to add this line in lpd.conf:

    lpd_listen_port=515

By default, printers don't allow other users to remove other people's print
jobs.  For an MP3 spooler, however, this may be a desirable trait, especially
if someone trys to rickroll you.  You can let everyone lprm jobs by
commenting out the line:

    REJECT SERVICE=M

XXX: On scourge, ACCEPT SERVICE=M SAMEHOST SAMEUSER doesn't seem to work
properly, so removing the REJECT line is a must!

XXXXXX: gutenbach accepts no responsibility for social faux pas that may
be committed with this system.  It is consider good etiquette, however,
to clear the status file if you're on zsr.

XXXXXXXX: Another note from jhamrick (09/2009): debathena-lprng does not start up with the system by default.  debathena developers are currently deciding whether to change this, but in the meantine you will want to do:

> ln -s ../etc/init.d/debathena-lprng /etc/rc2.d/S60debathena-lprng
> ^rc2^rc3
> ^rc3^rc4
> ^rc4^rc5
> ln -s ../etc/init.d/debathena-lprng /etc/rc0.d/K40debathena-lprng
> ^rc0^rc1
> ^rc1^rc6

7. Test, round one

The first test you should do to make sure gutenbach is configured properly is
to attempt to play an mp3 file locally, via lpr.  The command you should use
is:

    mit-lpr -Pprintername@localhost filename.mp3

Note the "mit-" prefix; Debathena defaults to CUPS, which we have not set
up yet.

See below for troubleshooting tips.


8. Test, round two

The second test you should do is try playing an MP3 remotely. The appropriate
command is:

    mit-lpr -Pprintername@hostname filename.mp3

(Once again, with "mit-").  See below for troubleshooting tips.


9. Troubleshooting

So, it didn't work.  How did it fail?

----
sending job 'ezyang@vivace+800' to asdfasdf@localhost
 connecting to 'localhost', attempt 1
 cannot open connection to localhost - No such file or directory
----

This means that lpd is not accepting connections properly.  Check to see
if you configured lpd.perms and lpd.conf correctly.  Try rebooting lpd
by pkill lpd && lpd.  Use nmap to check of port 515 is open, both on the
local machine and on a remote machine.  Check if networking is working
on the server.  Use netstat to see what programs are listening to port
515, and from which hosts.  Check iptables.

----
lpr: The printer or class was not found.
----

You're using lpr, not mit-lpr.

----
(no output, but no sound)
----

It looks like you managed to send the file over.  To diagnose the problems
further:

    * Check the zephyr logs of the class gutenbach was configured to
      send messages to:

        - If you see a reasonably full and formatted message, that means
          that either: 1. your volume is turned off, or 2. mplayer is
          horribly broken (XXX: it probably isn't, but I don't know what
          error message it gives in that case)

          By the way, be sure to check both the *hardware* and the
          *software* volume.

        - If you see a blank zephyr, that means that gutenbach-filter died
          trying to get a handle to /var/run/gutenbach/status and failing.
          Check if you created the file correctly, and that daemon has
          permissions to write to it. If you rebooted recently, check if
          you have the appropriate init.d script setup.

    * Otherwise, check /var/spool/lpd/printername/status.pr (most of all the
      other files are useless, especially including log):

        - If you see a Perl error, fix it. The most common cause is because
          exiftools is not installed.

    * Otherwise, double check the userland code in gutenbach-filter. XXX: There
      are some edge-cases that don't give nice error messages, for example
      the failed write to /var/run/gutenbach/status


10. Deploying CUPS
------------------

The final step is to give your newfangled printer a cups.mit.edu record.
In order to do this, you will need to ask IS&T for a Moira pcap entry
request.  Send mail to hesreq@mit.edu, specifying that you are setting
up a gutenbach clone, that you want a Moira pcap entry, the printer name
and server name of your queue, and that you want hwtype=LOCAL,ka=1. It wouldn't
hurt to also tell them where your print queue is, and a contact list.

Once you get the pcap entry, ping sipb-cups@mit.edu to add your machine
to the public list.

Troubleshooting:

----
Send_auth_transfer: on client client_krb5_auth failed - krb5_sendauth failed -
Bad application version was sent (via sendauth)
----

This means that the ka field in your Hesiod pcap entry is incorrectly set to
0.  Send mail to hesreq@mit.edu requesting ka be set to 1.


11. Setting up keytabs on the machine
-------------------------------------

Email accounts@mit.edu and ask them for two keytabs: one for your machine,
and one for "daemon" at your machine.  When you get the keytab, reset their
passwords by running:

    k5srvutil change -f your.keytab
    k5srvutil delold -f your.keytab

Now, install the machine-wide keytab in /etc/krb5.keytab, and install the
daemon keytab as /etc/daemon.keytab.  (The first filename is required; the
second can be changed.)  Make sure you chown and chgrp it to daemon.

Finally, edit /etc/printcap and give it information about the Kerberos:

gutenbach: server
    :cm=SIPB MP3 Spooler
    ...
    :auth_forward=kerberos5
    :use_auth=kerberos5
    :kerberos_id=daemon/your-machine-name.mit.edu@ATHENA.MIT.EDU
    :kerberos_keytab=/etc/daemon.keytab

Troubleshooting

-----
Printer 'pikamp3@LESBIAN-BABY-SEAGULL-GODDESS.MIT.EDU' - 
on client client_krb5_auth failed - krb5_sendauth failed - Bad response (during sendauth exchange)
-----

Your daemon.keytab is not readable by daemon.

12. Setting up remctl commands
-----------------------------

It's useful to be able to control the volume. Remctl is the way to do
this without asking people to ssh in, and then alsamix(er).

You will probably need to apt-get install remctl-server. Then, replace
the /etc/remctl/conf.d directory with a Git checkout of
/afs/sipb/project/sipbmp3/gutenbach-remctl.git.

Please note that remctl will NOT work without a keytab setup.


X. Deploying gutenbachweb
------------------------

gutenbach web provides a nice and user-friendly interface for some common
tasks. XXX: It is currently not portable beyond zsr. Stay tuned!

X. Troubleshooting
------------------

If things are broken on a reboot, make sure you're running:

    /etc/init.d/{gutenbach,zhm,debatehna-lprng}