B104 linux machine

CONTENTS

INTRODUCTION

This page contains directions for using the B104 its linux machine and getting sound and MIDI in and out of it.. This version is tailored for the MUSIC 271 course, spring 2005.

The "linux machine" lives in a closet with its screen, keyboard and mouse to the left of the mixer in B104. You can log onto it directly, or, (details later) remotely via the "ssh" program.

To get started you will need a linux machine account (get this from Miller). The door code to the room comes from ACS via the music facilities office. You should probably also get a standard ACS account for music graduate students.

I suggest you use the KDE environment, not Gnome (the default), since there is a bad interaction between Gnome and Pd that nobody knows how to fix.

GETTING KDE NOT TO GRAB THE AUDIO SYSTEM

Unfortunately, KDE likes to grab the machine's audio device. To use Pd in KDE you have to put KDE on the wrong audio I/O device so Pd can get the good one. Click on the "red hat" icon, bottom left, get "Control Center" (about 6 items from the bottom on the hat menu) and when the "control center" program starts up, open "Sound&multimedia" and start "sound system". Then in the "sound I/O" tab, enable "use custom sound device" and set it to the string: 

	/dev/dsp1
Then log out and back in and see if the instructions for starting "pdrp" below work.

The customary way to use UNIX is through "shells", which appear in windows. Unless you customize your account differently, you can make a shell window appear on a linux machine by right-clicking anywhere on the desktop and selecting "Open Terminal". (This is different in Gnome, in case you're using that, in which case it's an icon at the bottom of the screen.) You should get a new window with a prompt like "[msp@linux104 ~]$ ". This indicates that UNIX is waiting for you to type a command to it.

When you're through with your UNIX shell you can type

    exit
or sometimes a simple control-D. To log off the machine altogether you find the "log off" menu item. It's a good idea to remember to log off when you're ready to leave.

Note the font style conventions in the example above:

machine-name: anything in italics stands for something you type in.
ssh: anything in this style is what you type in exactly.

UNIX BASICS

This section describes what you should do once you're sitting at the linux machine and have one or more "shells" open on the linux machine.

When you issue a command to a UNIX shell, it usually responds by trying to find a program by that name and run it. Some programs are GUI-based, but the majority just do what you ask and then quit. This makes it easy to automate things, but on the other hand you have to learn what things do up front; there are no cute dialogs to lead you through operations like moving files around.

The UNIX filesystem is arranged as a hierarchy of "directories". Your shell is always in some directory or other, called the "current working directory". When you type out a "simple" filename it is assumed to be in the current directory. You can specify other directories besides the current one using slashes; so if you're in /home/fred for example (this means the subdirectory "fred" of the toplevel directory "home") you can type "tickle/salty" to refer to a file "salty" in the subdirectory "tickle". The "absolute" (full) pathname to the same file would be "/home/fred/tickle/salty". A filename starting with a slash is taken to be absolute; filenames starting with any other character are relative to the current Working Directory.

Here is a short (and incomplete) list of commands you will soon need. All but "nc" are generic UNIX commands.

Files and Directories

Back to top.

Print working directory
To find out in which directory you managed to end up, type:

    pwd

to "print your working directory."

WHen you start a new shell, you will find yourself in your home directory, such as /home/bosco.

Changing directories
The cd command stands for "change directory." You can move to the class directory or your home directory with this command.
Change to another directory
  1. Type the following command where directory_name stands for the directory to which you want to go.

    2. cd directory_name

Change to your home directory
Note that the ~ has magic powers. Alone, it stands for your home directory. When it precedes a user name, it means that person's home directory.
  1. Type:

    2. cd

    OR

    cd ~

You won't see anything happen.
Change to someone else's home directory
  1. Type the following, where username stands for the other person's home directory (e.g. khagan):

    2. cd ~username

Listing the contents of a directory
Next to pwd, ls ("list") is the most useful command for determining where you are. You may either list your current directory by not providing an argument, or you may list another directory by providing its pathname.

  1. To list the current working directory, type:

    2. ls

  2. To list another directory, type:

    3. ls pathname

Copying files
To copy a file, type:
    cp existing_file new_copy

If you specify two simple filenames (without slashes) the cp program works within the current directory. You may specify pathnames for either the source and/or the destination file. If the destination is an existing directory, the new file has the same name as the old one:

  1. Copying a file from someone else's home directory to the current directory:

    2. cp ~username/old-filename new-filename

  2. Copying a pd help file to the current directory:

    3. cp /usr/local/pd/doc/3.audio.examples/17.sampler.loop.pd .

  3. Alternatively:

    4. cd /usr/local/pd/doc/3.audio.examples

    cp 17.sampler.loop.pd ~

Removing files

To remove a file, type:

    rm filename

The filename can be a simple (slashless) filename or a pathname.

Moving files or directories

The syntax for moving files is the same as for copying them:

    mv old-filename new-filename

To move many files at once:
    mv filename1 filename2... destination-directory

Making directories
The mkdir command stands for "make directory." The command creates a directory in the current working directory unless you specify a pathname to another directory.
  1. Change to the directory in which you wish to create a directory.
  2. Type:

    3. mkdir directory_name

You won't see any changes. If you know the pathname to a directory, you can skip the step where you change to the directory in which you wish to create the new directory. Then you may simply type:

    mkdir pathname/directory_name

Copying directories
The cp command stands for "copy." This command may be used for directories or files (see Copying Files below). cp will copy the given file to the current working directory or a specified directory. Since a directory often has contents, you must specify that the command must work recursively. Therefore, the option -r causes cp to copy the contents within the target directory as well.

Type:

    cp -r pathname/target_directory_name pathname_to_destination

It is important to note that one may copy a directory and change the name of the copy by specifying a name for the destination directory withing the command. For example,

    cp -r ~/my_original_directory ~/destination/my_copy

will copy the my_original_directory, which lives in my home directory, to the directory named "destination." However, it will rename it to "my_copy."

Changing access permissions

Sometimes you won't be able to read your friends' files because your account won't have the necessary permission. Ask your friend to make the relevant files "public readable". Also you will need read and "execute" permission to the directories you need to search through to get the files in question. To make a file readable by anyone (but to allow only the owner to modify it, type

    chmod 644 filename1 filename2...

    chmod 755 directory1 directory2...

You can verify the settings using ls -l which gives you a readout as in: 
-rw-r--r--   1 msp      msp          5156 Jan 24  1999 1.ring-mod.pd
-rw-r--r--   1 msp      msp          5474 Jan 24  1999 2.bandpass.pd
-rw-r--r--   1 msp      msp         12805 Jan 25  1999 3.phase.vocoder.pd
-rw-r--r--   1 msp      msp           617 Jan 24  1999 README.txt

The "-rw-r--r-" should have 3 "r"s in it if the file is public readable.

to list the current directory itself (not its contents), type ls -l -d . For a directory you should get "rwxr-xr-x".

Reading the UNIX manual
To get help on a UNIX command, type, for example, man ls .

Editing text files
The good text editor is called "nedit." From a shell you can type, for instance,
    nc file1 file2...

SSH: remote login

You can use the "ssh" ("secure shell") program to login to other UNIX machines:

    ssh machine-name

    ssh user-name@machine-name

(You would use the second form is your username is different on the two machines.)

You can use the same protocol to get onto a UNIX machine from a PC or a Macintosh. To do this, find a free "ssh client" for your platform. For the PC, a good one is "putty" which you can find by typing "putty" to Google. I'm not sure which client to use from Mac OS9. From Mac OSX, just use "ssh", which you type to a terminal window.

SFTP: transferring files
Also assuming you find the right client to download, you can run a file-transfer program to get files into and out of the linux machine. From UNIX, type
    sftp user-name@machine-name

(or use the short form if the user names are the same.) From a PC, I use "psftp", also from the Putty web site; type the command to a terminal window.

"psftp" is an interactive, "text-based" program into which you type commands. When you invoke sftp, you should see a prompt like "sftp>". Useful commands from within sftp are:

There seems to be no automatic way to copy collections of files; to do this you probably should use the "scp" program:
    scp -r source-directory destination-machine:destination-directory

... which for a PC is "pscp", and in which you can supply user names in the same way as above.

RUNNING THE MUSIC 271 PATCHES

If you know the details of which audio and MIDI devices you want, you can run Pd directly by typing "pd" to a shell, probably with arguments to specify how you want things set up. But for the purposes of the Music 271 course, there's an auxilliary program named "pdrp" which handles the details for you. Type "pdrp" to a shell and see: 
    1) TEST-TONE             6) reich-phase         11) tenny-collage
    2) boulez-dialogue       7) risset-duet         12) yuasa-midnight
    3) chowning-stria        8) saariaho-noanoa     13) quit
    4) harvey-mortuous       9) steiger-loops
    5) manoury-pluton       10) stockhausen-mantra
    #?

Now type a number from 1 to 13. Start with "1", the test tone. When you're done with the test tone, quit Pd and you get the "pdrp" menu back. "13" quits and you get back to the shell prompt.

THE B104 LINUX MACHINE AUDIO SETUP

The linux machine has eight audio connections to and from the B104 patch bay. The outputs normally appear on the mixer's line inputs 1 through 8. The mixer's "control room" output goes to the stereo pair, and the mixer "buss" outputs can be patches to the 8 smaller speakers.

To start out, recall the "puckette" setting for the mixer (number 21). Just recalling a setting on the mixer can be complicated. First hit the "library" button (right of screen) until you see the preset library show up (other libraries control effects, etc; the button cycles between them). Then twiddle the knob until preset 21 shows. Then CHECK THE PRESET RECALL MODE which can defeat the setting from actually taking effect! Then hit the "recall" button (not the "enter" button which is probably how you messed up the recall settings in the first place.)

The input channel levels and the Control Room settings aren't presettable and have to be massaged by hand: input levels to 10 oclock or so, control room select to "stereo", and control room volume to 12 oclock.

Then run the PDRP test tone and see if you get anything.

To get sound from the mixer back to the computer, map the sound to one or more unused bus outputs and patch it to the audio sends to "computer number 1."

Usually you'll want to send the microphone to the computer. First, make sure the mic is plugged into the mixer. Verify that the green LED on the channel blinks when you tap on the mic. To get this to happen you must have the line/mic swithc on mic and the deadly "fader flip" button OFF. Then assign the mixer channel to bus 7/8, say, and enjoy the VU meters. Finally, check that they're patched to the computer properly, run the "pdrp" test tone patch, turn on "meters" there, and see if the numbers are in a good range (tapping the mic should give 80 or 90 dB; 100 is clipping.)

RECORDING AND EDITING SOUNDFILES

Type 

	audacity
to a shell to get a very powerful sound editor.

MIDI

B104 has a MIDI piano connected to the Linux machine.

The piano has to be put in "real time MIDI mode." After powering the piano up, hit "midi" and then hit the RECORD button until you see that MIDI out is "kbd" and not "DELAYOUT." You should test this using the "testtone" patch (via the "pdrp" command) before you try to use it.

Acknowledgement: the UNIX lore here is adapted from Kerry Hagan's UNIX page.