Tag debian

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2017-04-22 20:48:43+02:00

Splitting a git-annex repository

I have a git annex repo for all my media that has grown to 57866 files and git operations are getting slow, especially on external spinning hard drives, so I decided to split it into separate repositories.

This is how I did it, with some help from #git-annex. Suppose the old big repo is at ~/oldrepo:

# Create a new repo for photos only
mkdir ~/photos
cd photos
git init
git annex init laptop

# Hardlink all the annexed data from the old repo
cp -rl ~/oldrepo/.git/annex/objects .git/annex/

# Regenerate the git annex metadata
git annex fsck --fast

# Also split the repo on the usb key
cd /media/usbkey
git clone ~/photos
cd photos
git annex init usbkey
cp -rl ../oldrepo/.git/annex/objects .git/annex/
git annex fsck --fast

# Connect the annexes as remotes of each other
git remote add laptop ~/photos
cd ~/photos
git remote add usbkey /media/usbkey

At this point, I went through all repos doing standard cleanup:

# Remove unneeded hard links
git annex unused
git annex dropunused --force 1-12345

# Sync
git annex sync

To make sure nothing is missing, I used git annex find --not --in=here to see if, for example, the usbkey that should have everything could be missing some thing.

debian eng gitannex pdo sw
2017-04-09 20:54:06+02:00

Ansible config for my stereo

I bought a Raspberry Pi 2 and its case. I could not reuse the existing SD card because it wants a MicroSD.

A wise person once told me:

First you do it, then you document it, then you automate it.

I had done the first two, and now I've redone the whole setup with ansible, here: stereo.tar.xz.

Hifi with a Raspberry Pi 2 and its case

debian eng hw pdo raspi-hifi sw
2017-04-03 11:15:38+02:00

Free Software on my phone

I try to run my phone on Free Software as much as I can.

I recently switched to LineageOS. I took it as an opportunity to do a full factory wipe and reinstall, to simulate a disaster recovery.

Here's a summary of the basic software I use:

debian eng pdo phone sw
2017-04-02 00:10:00+02:00

Stereo remote control

Wouldn't it be nice if I could use the hifi remote control to control mpd?

It turns out many wishes can come true when one has a GPIO board.

A friend of mine had a pile of IR receiver components in his stash and gave me one. It is labeled "38A 1424A", and the closest matching datasheet I found is this one.

I wired the receiver with the control pin on GPIO port 24, and set up lirc by following roughly this guide.

Hifi with shutdown button and IR receiver

Enable lirc_rpi support

I had to add these lines to /boot/config.txt to enable lirc_rpi support:

dtoverlay=lirc-rpi,gpio_in_pin=24,gpio_out_pin=22
dtparam=gpio_in_pull=up

At first I had missed configuration of the internal pull up resistor, and reception worked but was very, very poor.

Then reboot.

Install and configure lirc

apt install lirc

I added these lines to /etc/lirc/hardware.conf:

DRIVER="default"
DEVICE="/dev/lirc0"
MODULES="lirc_rpi"

Stopped lircd:

systemctl stop lirc

Tested that the receiver worked:

mode2 -d /dev/lirc0

Downloaded remote control codes for my hifi and put them in /etc/lirc/lircd.conf.

Started lircd

systemctl start lirc

Tested that lirc could parse commands from my remote control:

$ irw
0000400405506035 00 CD_PAUSE RAK-SC304W
0000400405506035 01 CD_PAUSE RAK-SC304W
0000400405506035 02 CD_PAUSE RAK-SC304W
0000400405505005 00 CD_PLAY RAK-SC304W
0000400405505005 01 CD_PLAY RAK-SC304W

Interface lirc with mpd

I made this simple lirc program and saved it in ~pi/.lircrc:

begin
     prog = irexec
     button = CD_NEXT
     config = mpc next
end

begin
     prog = irexec
     button = TAPE_FWD
     config = mpc next
end

begin
     prog = irexec
     button = TAPE_REW
     config = mpc prev
end

begin
     prog = irexec
     button = CD_PREV
     config = mpc prev
end

begin
     prog = irexec
     button = TAPE_PAUSE
     config = mpc pause
end

begin
     prog = irexec
     button = CD_PAUSE
     config = mpc pause
end

begin
     prog = irexec
     button = CD_PLAY
     config = mpc toggle
end

begin
     prog = debug
     button = TAPE_PLAY_RIGHT
     config = mpc toggle
end

Then wrote a systemd unit file to start irexec and saved it as /etc/systemd/system/mpd-irexec.service:

[Unit]
Description=Control mpd via lirc remote control
After=lirc mpd

[Service]
Type=simple
ExecStart=/usr/bin/irexec
Restart=always
User=pi
WorkingDirectory=~

[Install]
WantedBy=multi-user.target

Then systemctl start mpd-irexec to start irexec, and systemctl enable mpd-irexec to start irexec at boot.

Profit!

All of this was done by me, with almost no electronics training, following online tutorials for the hardware parts.

To connect components I used a breadboard and female-male jumper leads, so I didn't have to solder, for which I have very little practice.

Now the Raspberry Pi is so much a part of my hifi component that I can even control it with the hifi remote control.

Given that I disconnected the CD and tape players, there are now at least 16 free buttons on the remote control that I can script however I like.

Raspberry Pi closeup

debian eng hw pdo raspi-hifi sw
2017-04-01 00:10:00+02:00

Shutdown button for my Raspberry Pi

My Raspberry Pi hifi component setup lacked a way to cleanly shutdown the system without ssh.

I wished the Raspberry Pi had a button so I can tell it to shutdown.

I added one to the GPIO connector.

It turns out many wishes can come true when one has a GPIO board.

This is the /usr/local/bin/stereo-gpio script that reacts to the button press and triggers a shutdown:

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#!/usr/bin/python3
# http://razzpisampler.oreilly.com/ch07.html
# http://web.archive.org/web/20160305001215/http://razzpisampler.oreilly.com/ch07.html
from RPi import GPIO
import time
import subprocess

def on_button(pin):
    print("Button pressed", pin)

GPIO.setmode(GPIO.BCM)

GPIO.setup(18, GPIO.IN, pull_up_down=GPIO.PUD_UP)

while True:
    pin = GPIO.wait_for_edge(18, GPIO.FALLING)
    if pin == 18:
        subprocess.check_call(["/bin/systemctl", "halt"])

This is the /etc/systemd/system/stereo-gpio.service systemd unit file that runs the script as a daemon:

[Unit]
Description=Stereo GPIO manager

[Service]
Type=simple
ExecStart=/usr/local/bin/stereo-gpio
Restart=always

[Install]
WantedBy=multi-user.target

Then systemctl start stereo-gpio to start the script, and systemctl enable stereo-gpio to start the script at boot.

debian eng hw pdo raspi-hifi sw
2017-03-31 09:06:22+02:00

Raspberry Pi as a Hi-Fi component

I have a 25 years old Technics hifi system that still works fine, and I gave it a new life by replacing the CD player and cassette player modules with a Raspberry Pi.

Technics hifi with a Raspberry Pi attached

Connection

Each component of the hifi has a mains input and a mains plug that is used to power the next component. The element where the main power lead goes in is the radio component, which has a remote control receiver, a watch and a timer, and will power on the rest of the system when turned on by its power button, the remote control, or the alarm function.

I disconnected the cassette and cd player modules, and plugged the Raspberry Pi phone charger/power supply in the free plug behind the amplifier module, at the end of the (now very short) power lead chain.

I also connected the audio output of the Raspberry Pi to the CD input of my stereo. The advantage of CD over AUX is that the remote control buttons for switching audio sources don't cover the AUX inputs.

With alsamixer I adjusted the output volume to match that of the radio component, so that I can switch between the two without surprising jumps in volume. I used alsactl store to save the mixer levels.

Now when I turn the hifi on I also turn the Raspberry Pi on, and when I turn the hifi off, I also cut power from the Raspberry Pi.

Operating system

Operating system install instructions:

  1. I downloaded a Raspbian Jessie Lite image
  2. I put it on an SD card
  3. I created an empty ssh file on the boot partition
  4. I put the SD card on the Raspberry Pi and turned on the stereo.
  5. ssh pi@raspberrypi password raspberry
  6. sudo raspi-config to change the hostname, the password, and to enlarge the root partition to include all the rest of the space available in the SD card.

Music Player Daemon

This is the set up of the music player part, with mpd.

apt install mpd

The configuration file is /etc/mpd.conf. The changes I made are:

Make mpd accessible from my local network:

bind_to_address         "any"

Make mpd discoverable:

zeroconf_enabled                "yes"
zeroconf_name                   "stereo"

Allow anyone who visits me to control the playlist, and only me to run admin functions:

password                        "SECRET@read,add,control,admin"
default_permissions             "read,add,control"

At my first try, mpd hung when changing songs. I had to disable dmix by uncommenting the device option in the audio_output configuration. use_mmap is cargo-culted from the archlinux wiki.

audio_output {
        type            "alsa"
        name            "My ALSA Device"
        device          "hw:0,0"        # optional
        use_mmap        "yes"
}

If at some point I'll decide to use other audio software on the system, I'll probably want to play via pulseaudio.

Sending music to the stereo

I made a little script to sync the music directory on my laptop with /var/lib/mpd/music:

#!/bin/sh

rsync -avz --filter=". sync-stereo.filter" --copy-links --prune-empty-dirs --delete ./ pi@stereo:/var/lib/mpd/music

ssh pi@stereo "chmod u=rwX,go=rX -R /var/lib/mpd/music"

It uses this sync-stereo.filter rules file for rsync:

hide /_archive
include */
include **.mp3
hide *

mpd clients

mpc

$ mpc -h stereo status
UltraCat - Unexpected Little Happenings
[playing] #15/22   0:03/4:06 (1%)
volume: 80%   repeat: off   random: on    single: off   consume: off

M.A.L.P.

On my phone I installed M.A.L.P. and now I have a remote control for mpd.

In its settings, I made a profile for home where I just had to set the hostname for the stereo and the admin password.

Cantata

On my laptop I installed cantata, set the hostname and password in the preferences, and had the client ready.

Profit!

Now I can take the remote control of my hi-fi, turn it on, and after a while mpd will resume playing the song that was playing when I last shut it down.

I also have realtime player status on my phone and on my laptop, and can control music from either at any time. Friends who visit me can do that as well.

Everything was rather straightforward, well documented and easy to replicate. The hardware is cheap and very easy to come by.

debian eng hw pdo raspi-hifi sw
2017-03-16 12:01:00+01:00

Django signing signs, does not encrypt

As is says in the documentation. django.core.signing signs, and does not encyrpt.

Even though signing.dumps creates obscure-looking tokens, they are not encrypted, and here's a proof:

>>> from django.core import signing
>>> a = signing.dumps({"action":"set-password", "username": "enrico", "password": "SECRET"})
>>> from django.utils.encoding import force_bytes
>>> print(signing.b64_decode(force_bytes(a.split(":",1)[0])))
b'{"action":"set-password","password":"SECRET","username":"enrico"}'

I'm writing it down so one day I won't be tempted to think otherwise.

debian django eng pdo sw
2017-01-11 12:43:32+01:00

Modern and secure instant messaging

Conversations is a really nice, actively developed, up to date XMPP client for Android that has the nice feature of telling you what XEPs are supported by the server one is using:

Initial server features

Some days ago, me and Valhalla played the game of trying to see what happens when one turns them all on: I would send her screenshots from my Conversations, and she would poke at her Prosody to try and turn things on:

After some work

Valhalla eventually managed to get all features activated, purely using packages from Jessie+Backports:

All features activated

The result was a chat system in which I could see the same conversation history on my phone and on my laptop (with gajim)(https://gajim.org/), and have it synced even after a device has been offline,

We could send each other rich media like photos, and could do OMEMO encryption (same as Signal) in group chats.

I now have an XMPP setup which has all the features of the recent fancy chat systems, and on top of that it runs, client and server, on Free Software, which can be audited, it is federated and I can self-host my own server in my own VPS if I want to, with packages supported in Debian.

Valhalla has documented the whole procedure.

If you make a client for a protocol with lots of extension, do like Conversations and implement a status page with the features you'd like to have on the server, and little green indicators showing which are available: it is quite a good motivator for getting them all supported.

debian eng pdo
2017-01-07 14:38:52+01:00

Teamwork

When I saw this video or this video I thought of this article.

When I feel part of a tightly coordinated and synchronized team I feel proud for the achievements of the team as a whole, which I see as bigger than what I could have achieved alone.

I also don't feel at risk of taking bad decisions. I feel less responsible. If I do what I'm told, I can't be blamed for doing the wrong things. I find it relaxing, every once in a while, to not have to be in charge.

I guess this could be part of the allure of a totalitarian regime: being freed from the burden of growing up

Thinking about this, reading those articles about romantic relationships, I see quite a bit of parallels also with organising cooperation and teamwork.

It looks like I ended up making parallels between Polyamory, Anarchism, and Free Software again. If you think there should traditionally be also a mention of BDSM, go back to "I find it relaxing, every once in a while, to not have to be in charge".

debian eng life pdo
2016-12-25 13:38:33+01:00

"Intervallo RAI" generator

During holiday idling, I made a thing to generate picture slideshows similar to RAI's iconic "Intervallo"

You can get it at https://github.com/spanezz/intervallo

Usage:

$ intervallo --help
usage: intervallo [-h] [--font file.ttf] [--audio file.mp3] [--duration sec]
                  imgfile [imgfile ...]

Create an Intervallo RAI out of a collection of images.

positional arguments:
  imgfile           input image files

optional arguments:
  -h, --help        show this help message and exit
  --font file.ttf   Font to use for subtitles
  --audio file.mp3  Audio track
  --duration sec    Time for each image in seconds

For example:

./intervallo --font DejaVuSerif.ttf --audio Paradisi-Toccata.mp3 *.jpg

The images are captioned with their file name, without extension. You may want to rename the image files to have nice descriptive names.

For some audio to use, you can try https://archive.org/details/IntervalloRai-Paradisi

Example

https://www.youtube.com/watch?v=ZCERwjTB4ck

debian eng pdo sw