Adds research/raspberrypi

research/raspberrypi.mdwn

+[[!meta title="Raspberry Pi"]]
+
+* [General information](https://wiki.debian.org/RaspberryPi2).
+
+Issues
+======
+
+## SSH
+
+SSH not working by default on newer (2017) raspbian releases. That's because it's disabled
+by default. Solution is to create a file called 'ssh' in the boot partition.
+
+## Networking
+
+* You might try to make it allways up with wicd-curses.
+
+### Amplifier mode
+
+Some references on using an external soundcard as an amplifier:
+
+* packages: libncurses5-dev libjack-jackd2-dev jack-tools
+* http://wiki.linuxaudio.org/wiki/raspberrypi
+* http://www.jackaudio.org/applications/
+* http://linux-audio.4202.n7.nabble.com/Solution-for-jackd2-and-dbus-without-X-session-td35904.html
+* http://comments.gmane.org/gmane.linux.audio.users/82560
+* [sound - How do I output my audio input? - Ask Ubuntu](https://askubuntu.com/questions/2719/how-do-i-output-my-audio-input)
+* [Crackle-free audio on the Raspberry Pi with mpd and PulseAudio – dbader.org](https://dbader.org/blog/crackle-free-audio-on-the-raspberry-pi-with-mpd-and-pulseaudio)
+* [How to play realtime insted of using arecord and aplay?](https://www.linuxquestions.org/questions/linux-newbie-8/how-to-play-realtime-insted-of-using-arecord-and-aplay-858500/)
+* [Jackd Headless](https://capocasa.net/jackd-headless).
+
+Attempts:
+
+    man jack_disconnect 
+    man jack_connect 
+    man jack_lsp
+    sudo jack_lsp
+    sudo apt-get install jack-tools
+    jackd
+    jackd --no-realtime
+    jackd --no-realtime -d alsa
+    export DBUS_SESSION_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket jackd --no-realtime -d alsa
+    DBUS_SESSION_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket jackd --no-realtime -d alsa
+    sudo jackd --no-realtime -d alsa
+    DBUS_SESSION_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket sudo jackd --no-realtime -d alsa
+    sudo apt-get install libncurses5-dev libjack-jackd2-dev -y
+    DBUS_SESSION_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket sudo jackd --no-realtime -d alsa
+    DBUS_SESSION_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket sudo jackd -r -d alsa -d default:CARD=USB
+
+### Freezing
+
+At the serial console:
+
+    [123916.394903] INFO: rcu_preempt detected stalls on CPUs/tasks:
+    [123916.413406]         1: (1 GPs behind) idle=dcd/140000000000000/0 softirq=1003110/1003111 fqs=312910 
+    [123916.447541]         (detected by 0, t=765007 jiffies, g=729122, c=729121, q=347657)
+    [123916.467769] Task dump for CPU 1:
+    [123916.484152] puppet          R running      0 29362      1 0x00000002
+    [123916.503500] rcu_preempt kthread starved for 448421 jiffies!
+
+References:
+
+* [Pi2 rcu_preempt detected stalls · Issue #1161 · raspberrypi/linux · GitHub](https://github.com/raspberrypi/linux/issues/1161).
+
+## Montagem automática de volume cifrado
+
+Assumindo:
+
+    VOLNAME: nome do disco externo
+    MEDIA: nome do dispositivo mapeado (device mapper)
+
+No TPC:
+
+    dd if=/dev/urandom of=pirotron bs=1024 count=4
+    keyringer $PROJECT encrypt disks/$MEDIA/luks/root-berry $VOLNAME
+    scp $VOLNAME berry:~/
+    wipe $VOLNAME
+
+No raspberry:
+
+    sudo mv /home/$USER/$VOLNAME /root/
+    sudo chmod 0400 /root/$VOLNAME
+    sudo cryptsetup luksAddKey /dev/sda1 /root/$VOLNAME
+
+No `/etc/crypttab`:
+
+    $VOLNAME        /dev/sda1               /root/$VOLNAME  luks
+
+No `/etc/fstab`:
+
+    /dev/mapper/$VOLNAME /media/$VOLNAME ext4    defaults          0       2
+
+Referências:
+
+* https://www.howtoforge.com/automatically-unlock-luks-encrypted-drives-with-a-keyfile
+* https://askubuntu.com/questions/450895/mount-luks-encrypted-hard-drive-at-boot
+
+## Rede
+
+Arquivo `/etc/network/interfaces`:
+
+    auto lo
+    iface lo inet loopback
+
+    #auto eth0
+    #allow-hotplug eth0
+
+    #iface eth0 inet manual
+    #iface eth0 inet static
+    #  address 192.168.0.100
+    #  netmask 255.255.255.0
+
+    auto wlan0
+    allow-hotplug wlan0
+
+    iface wlan0 inet static
+      address 192.168.0.100
+      netmask 255.255.255.0
+      wpa-ssid ACCESS_POINT_NAME
+      wpa-psk PSK
+      #wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
+      post-up /usr/sbin/service shorewall restart
+
+    #iface wlan0 inet manual
+    #  wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
+    #
+    #iface ape inet static
+    #  address 192.168.0.100
+    #  netmask 255.255.255.0
+
+    #iface wlan0 inet manual
+    #wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
+
+    #auto wlan1
+    #allow-hotplug wlan1
+    #iface wlan1 inet manual
+    #wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
+
+Arquivo `/etc/wpa_supplicante/wpa_supplicant.conf` (por enquanto não utilizado):
+
+    ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
+    update_config=1
+
+    network={
+        ssid="ACCESS_POINT_NAME"
+        psk="PSK"
+    }
+
+O esquema `wpa-roam` não funciona com interfaces `static`, então foi necessário usar [https://git.fluxo.info/?p=puppet-nodo.git;a=commit;h=d09f347afc0a99481673f227f83864d06206add6 um script].
+
+Backups
+-------
+
+Fazendo o backup do cartão microSD a partir do TPC:
+
+    dcfldd if=/dev/sdb | bzip2 > raspberry.img.bz2
+
+## References
+
+* http://linuxonflash.blogspot.com.br
+* http://elinux.org/RPi_Serial_Connection
+* https://www.raspbian.org/RaspbianMirrors