Raspberry Pi

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Latest revision as of 13:52, 20 February 2020

[edit] Cookbook

My collection of hints, tips and tricks (supporting my memory and maybe also helping others).

[edit] External USB drives

Automount USB-Drives in Raspbian
- One may use USBmount and autofs
- I prefer udevil, see below

Install ntfs-3g if you need write access to ntfs file systems

How to increase performance?
- Mount with option 'noatime' or 'relatime'
- Mount without option sync (e.g. keep default async)
- If using ntfs-3g (fuse) file system, try mounting with option 'big_writes', see for example http://obihoernchen.net/wordpress/tag/big_writes/

[edit] udevil

example for manual mounting:

udevil mount /dev/sda1

auto-mounting via udev-rule, see for example http://lsdlinux.org/wiki/doku.php?id=auto_mounting#using_udev_rule (I just copied the 95-udevil-mount.rules file from an OpenElec installation (http://www.raspberrypi.org/downloads) )

my build-steps (maybe there's a simpler way, but this worked...):
- download 0.4.3/udevil_0.4.3-1_all.deb from https://github.com/IgnorantGuru/udevil/tree/pkg, e.g. using wget
- extract deb-package via ar vx udevil_0.4.3-1_all.deb
- extract data archive tar xzvf data.tar.gz
- change to tar usr/share/devil/src
- untar tar xvfJ udevil-current.tar.xz
- cd udevil-0.4.3
- mv distros/debian
- execute dpkg-buildpackage
- If all required packages are installed, this results in udevil_0.4.3-1_armhf.deb. If the build fails due to missing packages, install the missing packages, and re-do the dpkg-buildpackage step
- Install via sudo dpkg -i udevil_0.4.3-1_armhf.deb

[edit] Samba server / NAS

How to install?
- | Raspberry Pi: Samba Server installieren (German)
- Low Budget NAS mit einem Raspberry PI (German)

Slow disc performance?
- see 'Slow USB drives' above
- use Raspbian, etc without GUI to get as much CPU power for file-transfer as possible (OpenELEC or RaspBMC constantly use about 10-20% CPU load when idle, use top to check!)

Configuration and tuning
- https://calomel.org/samba.html
- https://calomel.org/samba_optimize.html

If your /var/log/samba/log.smbd fills up with printing/print_cups.c:110(cups_connect) Unable to connect to CUPS server localhost messages, try http://www.sotechdesign.com.au/samba-log-showing-error-failed-to-retrieve-printer-list/
I also created an empty /etc/printcap to avoid Unable to open printcap file /etc/printcap for read messages.

I don't need sound:

root@pi ~ # cat /etc/modprobe.d/snd-blacklist.conf 
# I don't need sound
blacklist snd
blacklist snd_pcm
blacklist snd_soc_core
blacklist snd_soc_bcm2708_i2s

[edit] Trying to reduce number of disk writes (SD card)

I'm using RRD with a cron job (currently observing pi's temperature and frequency). I hope that my SD card has proper wear-leveling (and currently my 8 GB card is less than half full), so that the frequent writing should not be a problem. But still, I want to reduce the number of writes to the SD card (in order to not bust it's lifetime).

Here's what I've done:

Edit /etc/default/cron and set EXTRA_OPTS="-L 0" to disable logging (I don't need these)
Avoid entries like pam_unix(cron:session): session closed for user pi in /var/log/auth.log
- Edit /etc/pam.d/cron and comment the line @include common-session-noninteractive ([1])

Edit /etc/pam.d/common-session-noninteractive as shown here: http://ubuntuforums.org/showthread.php?t=1256801&p=10283830#post10283830

I've implemented a persist tmpfs as discussed in http://www.a-netz.de/2013/02/persistent-storage-with-ramdisks/ and http://www.observium.org/wiki/Persistent_RAM_disk_RRD_storage (and, I guess, many other sites)
- moved all the .rrd files as well as the created images to my persistent-ramdisk location
- moved some directories with frequent writes to my persistent-ramdisk location and added corresponding sym-links
  - /var/spool
  - /var/log
  - /var/cache/samba
- edited /etc/insserv.conf to add the persist-ramdisk as a requirement to $local_fs; the original definition can still be accessed as $local_fs_orig:

$local_fs_orig  +mountall +mountall-bootclean +mountoverflowtmp +umountfs
# we need the sym-link data in /var/log and /var/spool to be available
$local_fs       $local_fs_orig +persist-ramdisk

/etc/init.d/persist-ramdisk depends on $local_fs_orig, and the other init-scripts keep their dependency to $local_fs. This ensures that /var/log and /var/spool are ok when starting & stopping other init scripts.

set RAMTMP to yes in /etc/default/tmpfs to get tempfs based /tmp

Before changing /tmp:

But still, iostat shows quite some data written to the SD card, according to iotop its jbd2, the ::journaling part of ext4 (pi is 'idle', only some services run, and the ext4 partition is mounted with noatime).

I need to do more digging...

After changing /tmp:

It looks like the unwanted writes to SD are gone. I'll watch it for some time...

[edit] Useful stuff and Q&A

Q: Why does my Pi restart when hotplugging a USB drive?
- http://thestuffsido.blogspot.de/2013/05/fixing-raspberry-pi-hotplugging.html
- http://therandomlab.blogspot.de/2013/01/raspberry-pi-mod-to-avoid-shutdown-on.html

Q: Does Raspberry support WOL?

A: No: the Ethernet chip is connected via USB (http://www.raspberrypi.org/forum/viewtopic.php?f=53&t=39714)

Q: The new password is to short, or too simple

A: Try adjusting the PAM settings in /etc/pam.d/common-password:

remove the 'obscure' setting for pam_unix.so, and add your desired minimum length (e.g. minlen=2)

password [success=1 default=ignore] pam_unix.so sha512 minlen=2

!! This is not recommended if your box is connected to the internet or if it contains private data noone should know !!

But it's nice for testing (if you cannot or do not want to use auto-login.)

Q: How to configure static IP?

A: In /etc/network/interfaces:

iface eth0 inet static
address 192.168.0.31
netmask 255.255.255.0
gateway 192.168.0.1

Q: How to read core temperature, etc?

A: vcgencmd:

vcgencmd measure_temp
vcgencmd measure_clock arm

External USB HDD spin down
- hdparm does not work with my WD Elements (SG_IO: bad host status: 0x7)
- hd-idle works:

hd-idle -a sda -i 600

for details, see for example http://blog.is-a-geek.org/festplatten-in-den-standby-modus-versetzen-unter-ubuntu-desktopserver-mit-hd-idle (German)

Q: How to avoid update of a certain package?

A: Put package on hold ([2] (German)):

echo <packagename> "hold" | dpkg --set-selections

wikipedia:Raspcontrol with nginx
- http://www.foxplex.com/sites/raspcontrol-webinterface-auf-dem-raspberry-pi/ (German), http://www.foxplex.com/sites/performanter-nginx-webserver-auf-dem-raspberry-pi-mit-php-und-apc/ (German)
- http://menzerath.eu/artikel/raspberry-pi-raspcontrol-installation-funktionen/ (German)

Q: How many bytes are written to my (SD) disc?

A: Use iostat http://www.mybinarylife.net/2012/08/linux-iostat-command.html

A: Use iotop http://guichaz.free.fr/iotop/

A: Raw data of the kernel can be found in files /proc/diskstats and /sys/block/DEVNAME/stat https://www.kernel.org/doc/Documentation/iostats.txt

Q: How to reduce number of ext-fs checks?

A: tune2fs -c 60 /dev/sda1 Change maximum mount count to 60

A: tune2fs -i 12m /dev/sda1 Change check interval to 12 months

fore more details: http://wiki.ubuntuusers.de/Dateisystemcheck (German)

Q: Fix smsc95xx 1-1.1:1.0: eth0: kevent 2 may have been dropped

A: http://wood1978.techarea.org/~wood/wordpress/2013/04/03/fix-smsc95xx-1-1-11-0-eth0-kevent-2-may-have-been-dropped-on-raspberry-pi-with-arch-linux

Modifying the sysctl.conf values reduced the kevent-2 messages; I did not yet set smsc95xx.turbo_mode=N

[edit] Overclocking

I only set overclocking via raspi-config

Turbo: (Short) Raspberry stress test were ok. But I got an SD card error/corruption when doing a download and a dd-image of the SD card (according to http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=57907 the SD card error could be OC related.)

Luckily, I could recover all my data, see below.

Medium: Raspberry is stable. I've observed two file system corruption which might be related to overclocking (see [3] and its links).

Underclocking to 600 MHz

echo "600000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

Raspberry was stable for some hours, but it got frozen later on. I don't now if really related to underclocking. As the temperature did not drop significantly (stayed around 45°C), and the Raspberry CPU has no sleep modes either (for power saving), I did not retry.

Adjusting the ondemand-governor
- https://www.kernel.org/doc/Documentation/cpu-freq/governors.txt
- set /sys/devices/system/cpu/cpufreq/ondemand/sampling_down_factor to 10 [4]
  I had hoped this reduces the 1-wire CRC errors/device-disconnects problems, but with heavy (IO-) load (e.g. backup), 1wire sensors still get disconnected.

Nice power consumption analysis

[edit] Stress test and benchmarks

[edit] SD card issues

After my (Turbo-overclocked) Raspberry fried my 8 GB SD card, I had not hoped to to be able to recover any data, but I tried anyway. The card was only 1 week old, I have not written that much data too it (<4 GB, mainly the Raspbian image). I could still use this card for some time (see below), but finally I got a corrupted file system and could no longer repair it. That's when I re-installed Raspbian on a new SD card.

Maybe I should try running from USB sometime?

[edit] Recovery

Creating a binary image of the SD card with my PC using Win32 Disk Imager resulted in IO errors at about 17%.
The partition table of my SD card was still ok. I hoped to at least recover some text data of my ext4 partition, and thus I created an image using dd conv=sync,noerror if=/dev/sdb2 of=rasp-image.img bs=1M on my Linux machine (option conv=noerror ignores any errors, sync pads read-errors with zeros). The resulting image could not be mounted using a loop device.
Fortunately, fsck.ext4 raspberry-image.bin was able to repair the image, which I then could successfully mount on my Linux machine using mount -o loop rasp-image.img /mnt, and at a first glance, everything looked ok. So, I was at least able to get to my data.
On a later 'event', I dd-ed the repaired image back to the Raspberry, and could boot again.
On another a later 'event', I just fsck-ed the /dev/sdb2 using Linux, and could boot again... but I did not have luck this time - some files were gone.
I was just about to return the SD card, but for curiosity, I tried what happens if I re-install the (original) Raspbian image. To my surprise, Win32 Disk Imager did not report any error. And even more surprising, after writing the image, I was able to create an image of the whole disk without error. It looks like the card remapped some spare sectors.
My Raspberry successfully booted from this new image. I then used raspi-config to expand the root-fs (I've done this on my first installation as well). With Linux I was able to dd my repaired image to the repaired SD. The card booted as if nothing had happened...
But after some weeks, my Raspberry fried the SD card again, and some weeks later again ... And finally I could not get my pi to boot with this card. However, I can still read the data linux. Moving data to a new card... (easier said than done if the new card is slightly smaller... but, see below for resizing... and sometimes a fresh install is even less painful).

[edit] Reminders: dd, dd_rescue, losetup, mount and others

Example partition table printed by fdisk:

/dev/sdb: 7861 MB, 7861174272 bytes, 15353856 sectors
Units = Sektoren of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Gerät  boot.     Anfang        Ende     Blöcke   Id  System
[...]
/dev/sdb3        15288320    15353855       32768   83  Linux

Byte-offset of sdb3: 7827619840 = 15288320 * 512

Mount partition to /dev/loopN partition for repair, etc.

losetup -o 7827619840 --find --show /dev/sdb

--show prints the used /dev/loopN device

Directly mount partition using loop device:

mount -o loop,offset=7827619840 /dev/sdb /mnt

[edit] Some 1-Wire Stuff

[edit] Temperature Sensor DS1820

How to?
I have two DS18B20 and log temperatures using rrdtool.

When copying data via samba, I frequently get read-errors (CRC errors), or device-disconnects (/sys/bus/w1/devices/<id>/w1_slave temporarily not available).
- Q: Is this due to overclocking with using dynamic governor?
- A: No - also occurs without overclocking (but less frequent?)
- Q: Or is this due to voltage-problems?
- A: No - also occurs without over-voltage
- Q: Or something else?
- A: I have the impression that this is connected to electrical problems (e.g. timing, voltage) on my 1-wire when there's a lot of IO (USB, ethernet). Using 3 sensors works almost all the time (without overclocking), but using 4 or more sensors (2 connected star topologies, very bad for 1-wire GUIDELINES FOR RELIABLE LONG LINE 1-WIRE NETWORKS), almost always fails to read values on most of the sensors.
- A:Implement multiple 1-wire interfaces (see below), using 1 for each star-topology solved the problem. Reading 2x3 works perfect!
- A: If not adding new devices, disabling 1-wire search after module-loading resolves the device-disconnect issue. Simply put

wire search_count=5

in your /etc/modules (I'm not using DTB) to allow only 5 (initial) searches.

[edit] Multiple 1-wire buses

multiple w1 buses with device trees:

Add the following to /boot/config.txt:

 dtoverlay=w1-gpio,gpiopin=4
 dtoverlay=w1-gpio,gpiopin=22

OBSOLETE! Inspired and guided by http://www.raspberrypi.org/forums/viewtopic.php?p=513312#p513312, I've patched my 3.12.y kernel arch/arm/mach-bcm2708/bcm2708.c (patch file http://holyhead.de/RaspberryPi/bcm2708-multiple_w-1.patch-3.12.21.txt). Applying this patch to newer kernel versions is straight forward. (Currently I'm running 4.1.10 without device tree.)

Note: Some kernel versions ago, device trees were introduced for Raspbian, see for example http://www.raspberrypi.org/documentation/configuration/device-tree.md
So far, I don't know if this works with device trees.

OBSOLETE! I've cross-compiled the kernel on a linux-VM, using the instructions of http://elinux.org/RPi_Kernel_Compilation (compiling on the RaspberryPi takes 6 hours [5] or much more [6]).

[edit] Some 1-wire internals

[edit] Compiling own kernel

Some hints on cross-compiling:

extract kernel config from image:

scripts/extract-ikconfig kernel-image

(extract-ikconfig is part of the kernel sources)
newer kernels may store their config in a module: modules/4.*/kernel/kernel/configs.ko

[edit] Device Trees

http://xillybus.com/tutorials/device-tree-zynq-1

[edit] What about updates?

As I always forget this

apt-get update - update package lists
apt-get upgrade - upgrade installed packages
rpi-update - update kernel and modules

use SKIP_KERNEL=1 rpi-update to update the RPi firmware, but keep the current kernel

set SKIP_REPODELETE=1 to keep downloaded files (by default: /root/.rpi-firmware)

Kernel Sources

https://github.com/notro/rpi-source gets the source data from https://github.com/Hexxeh/rpi-firmware and https://github.com/raspberrypi/linux/

[edit] Hints for reading Kernel Panics

http://ptgmedia.pearsoncmg.com/images/013147751X/downloads/013147751X_book.pdf

p290:

export CONFIG_DEBUG_INFO=1
make kernel/sysctl.o
objdump -d -S kernel/sysctl.o > kernel/sysctl.dump

or, with my in cross-compiling setup:

DOMAKE drivers/w1/slave/w1_therm.o
${CCPREFIX}objdump -d -S w1_therm.o

http://www.opensourceforu.com/2011/01/understanding-a-kernel-oops/

http://www.lowlevel.eu/wiki/ARM-OS-Dev_Teil_2_%E2%80%93_Assembler_101

[edit] Attaching a LCD display (HD44780 controller)

[edit] Wiring and Specs

Specs
- ftp://imall.iteadstudio.com/IM120424018_EONE_2004_Characters_LCD/SPE_IM120424018_EONE_2004_Characters_LCD.pdf
- http://www.adafruit.com/datasheets/HD44780.pdf

http://www.schnatterente.net/technik/raspberry-pi-32-zeichen-hitachi-hd44780-display (German)

http://www.pro-linux.de/artikel/2/1624/5,die-anzeige-hardware-und-software.html

https://learn.adafruit.com/drive-a-16x2-lcd-directly-with-a-raspberry-pi/wiring

https://github.com/perryflynn/raspberrypi-misc/tree/master/charlcd_4x20_cmd

http://obrazki.elektroda.pl/5028699400_1384164963.jpg

[edit] Misc

http://www.makerspaceuk.com/lcd-temp-sensor/

http://anwendungsentwickler.ws/blog/kategorien/raspberry-pi/4x20-lcd-screen-mit-dem-raspberry-pi.html (German)

[edit] Controlling the display

Python RPi.GPIO

[edit] LCDProc hints

Pi & GPIO powered HD44780 LCD: http://www.boeeerb.co.uk/pi-lcd/

https://metacpan.org/pod/Net::LCDproc

http://www.raspberrypi.org/forums/viewtopic.php?f=35&t=63412

http://lcdproc.sourceforge.net/docs/current-user.html

http://lcdproc.sourceforge.net/docs/current-dev.html

http://tuxgraphics.org/electronics/200504/article375.shtml

[edit] Todo and Miscellaneous

[edit] OpenELEC

http://wiki.openelec.tv/index.php/Guide_to_add_your_own_remote

[edit] Lirc

http://powerpi.de/jede-infrarot-fernbedienung-am-raspberry-pi-2-nutzen-so-installierst-du-guenstig-einen-ir-empfaenger-teil-1/ (German)

[edit] Backports

[edit] Collection of misc stuff to check - things I might) try sometime

http://www.raspipress.com/2013/05/install-and-run-raspbian-from-a-usb-flash-drive/

f2fs

https://github.com/yuraa/Raspberry-Pi-Heartbeat

http://raspberrywebserver.com/serveradmin/back-up-your-pi-to-your-google-drive.html

Mathematica on Raspberry Pi, for free

also works in RasPi emulator, e.g. http://www.heise.de/ct/inhalt/2014/7/160/ (German, teaser to article)

NAS/Samba

try adjusting 'socket options' in (/etc/samba/smb.conf) to increase NAS performance: some websites recommend to disable the 'socket options', some recommend to set:

socket options = TCP_NODELAY IPTOS_LOWDELAY SO_RCVBUF=65536 SO_SNDBUF=65536

http://linuxtortures.blogspot.fr/2012/06/cross-compiling-and-cross-debugging-c.html

[edit] Things done

Adjust swap file (size, location -> (ext4) HDD - too slow?): http://manpages.ubuntu.com/manpages/hardy/man8/dphys-swapfile.8.html

[edit] Some links (aka bookmark lists)

Project sites

Blogs, forums, etc

http://www.raspberrypi.org/phpBB3/
Stm Labs Forum / Raspbmc
Wel!s Blog (German)
Raspberry Pi Blog of Jan Karres (German)
http://www.forum-raspberrypi.de/ /(German)
http://raspberrycenter.de/ (German)
http://archlinuxarm.org/forum/viewforum.php?f=31&sid=57987232ca9177c35eb3ef7fdf6b3341

wikipedia:Raspberry_Pi Raspberry Pi in Wikipedia

Miscellaneous

Manuals

https://github.com/raspberrypi/documentation

The Debian Administrator's Handbook

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