Exploring the Raspberry Pi with Fedora Linux¶
You have been using Linux on your big computers so far and want a light reading about exploring the Raspberry Pi? Or, you are just learning Linux with the Raspberry Pi? Hop on. This guide is for you.
However, this guide is aimed at wannabe power users of the Raspberry Pi. You won’t even see the window manager or the GUI if you follow this guide. All work is performed on the Pi in a headless manner - you ssh into your Pi. If that puts you off, you are better off fetching any of the other guides.
Let’s get started.
Installing Fedora Linux¶
Start from here.
Installer:
Downloading image:
Write to the disk:
Install complete:
Setting up for remote access¶
SSH server should already be installed and started in your Fedora installation. To check:
# service sshd status
Redirecting to /bin/systemctl status sshd.service
sshd.service - OpenSSH server daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled)
Active: active (running) since Thu, 01 Nov 2012 12:06:23 +1000; 9h ago
Main PID: 223 (sshd)
CGroup: name=systemd:/system/sshd.service
└ 223 /usr/sbin/sshd -D
and then:
# ssh localhost
root@localhost's password:
Last login: Thu Nov 1 21:13:07 2012 from zion.gateway
# who
root pts/0 2012-11-01 21:13 (zion.gateway)
root pts/3 2012-11-01 22:07 (localhost)
We are setup for remote login now. So you may now disconnect the TV jack from your Raspberry Pi. The network cable must stay on.
Web-based Access¶
Using wssh you can SSH into your Pi using a browser. Here’s how. Install the dependencies
# yum -y install python-devel libevent-devel python-setuptools
# pip-python install gevent flask paramiko gevent-websocket wssh
Now, start wsshd
# wsshd
wsshd/0.1.0 running on 0.0.0.0:5000
Now, from any other computer on your network, visit the URL, <raspi-ip>:5000 and you will see a login screen where you can enter the username, hostname/IP you want to connect to and use the password/private key authentication to connect to the remote host. Since the wssh daemon is running on your Pi, specifying localhost would mean the Pi itself and use the IP address for any other computer on your network. The login screen looks like this:
And then you can use the terminal, like you would normally do:
It is a good idea to run wsshd in the background using a daemonizer program like zdaemon (more on this later). Install zdaemon using
# pip-python install zdaemon
Run wsshd using zdaemon
# zdaemon -p wsshd start
. . .
daemon process started, pid=5277
Effectively, this gives you an entry point to your local home network from the Web browser. To make this possible outside your home network and being able to access it from anywhere, literally, you can setup tunelling. You can either play with your router configuration to set up port forwarding or simply use a tunelling service such as PageKite. Install it using
# curl -s https://pagekite.net/pk/ |sudo bash
Before starting to use this service, you should make yourself familiar with the pricing of the service.
Before you can start using the service, you have to sign up using
# pagekite.py --signup
Once you are done with that, you can setup your Pi for exposing the 5000 port using
# pagekite.py 5000 mypi.pagekite.me
And you should have your SSH login screen at your chosen kitename: http://mypi.pagekite.me in this case.
Updating and Adding RPM fusion¶
Install RPMFusion repositories:
# yum localinstall --nogpgcheck
http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm
http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-stable.noarch.rpm
Update system:
# yum -y update
Kernel version:
# uname -r
3.2.27
Time Synchronization¶
The Pi does not have a real time clock, which means the Pi cannot keep track of time across reboots. The solution is to run the ntpd daemon and use a NTP server to synchronize the time everytime you reboot.
Install the ntpd and ntpdate utilities:
# yum -y install ntp ntpddate
Although, the default NTP servers works, you may want to edit the /etc/ntp.conf to include NTP servers closer to your geographic location.
And start the ntp service
# service ntp start
The date and time should now be reflected to be your local time. To start the ntp service on boot
# chkconfig ntpd on
You will see that few seconds after the boot, the time is always set to the local time.
If you have the need to add one, see Adafruit’s tutorial.
Know your Raspberry Pi¶
We shall use simple Linux commands to know more about the Raspberry Pi.
Exploring /proc¶
The /proc file system is the place to look for all sorts of information. For example:
# cat /proc/cpuinfo
Processor : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS : 697.95
Features : swp half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xb76
CPU revision : 7
Hardware : BCM2708
Revision : 0003
Serial : 00000000f90cbb6b
The output tells us that we are on a system with an ARM processor with a BogoMIPS of 697.95. Among the CPU features..
You can obtain the information about the memory usage from the file /proc/meminfo:
# cat /proc/meminfo
MemTotal: 234968 kB
MemFree: 56840 kB
Buffers: 10380 kB
Cached: 126004 kB
..
..
Various other information about your system can be obtained such as:
# cat /proc/sys/kernel/hostname
raspberry
# cat /proc/sys/kernel/ostype
Linux
# cat /proc/sys/kernel/osrelease
3.2.27
# cat /proc/sys/kernel/pid_max
32768
# cat /proc/sys/kernel/poweroff_cmd
/sbin/poweroff
USB Devices¶
To explore the USB devices connected to your Pi, we can use the lsusb command
# lsusb -t
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
|__ Port 1: Dev 2, If 0, Class=hub, Driver=hub/3p, 480M
|__ Port 1: Dev 3, If 0, Class=vend., Driver=smsc95xx, 480M
The above output corresponds to no USB devices connected to the Pi. If you connect any other device(s), the command’s output will change accordingly. For example, when I plugged in two external storage disks, here is the what the output corresponds to
# lsusb -t
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
|__ Port 1: Dev 2, If 0, Class=hub, Driver=hub/3p, 480M
|__ Port 1: Dev 3, If 0, Class=vend., Driver=smsc95xx, 480M
|__ Port 2: Dev 6, If 0, Class=stor., Driver=usb-storage, 480M
|__ Port 3: Dev 5, If 0, Class=stor., Driver=usb-storage, 480M
Mount points and mounting disks¶
The df and mount commands can be used to obtain information about the secondary storage disks attached to your Raspberry Pi:
# df -h
Filesystem Size Used Avail Use% Mounted on
rootfs 3.7G 2.1G 1.4G 61% /
/dev/root 3.7G 2.1G 1.4G 61% /
devtmpfs 115M 0 115M 0% /dev
tmpfs 115M 0 115M 0% /dev/shm
tmpfs 115M 1.1M 114M 1% /run
tmpfs 115M 0 115M 0% /sys/fs/cgroup
tmpfs 115M 0 115M 0% /media
/dev/mmcblk0p1 51M 16M 36M 31% /boot
# mount
/dev/root on / type ext4 (rw,noatime,user_xattr,barrier=1,data=ordered)
devtmpfs on /dev type devtmpfs (rw,relatime,size=117396k,nr_inodes=29349,mode=755)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
..
..
The mount command is also used to mount external disks. Insert your external USB disk and note the output of dmesg
# dmesg
[79827.845946] usb 1-1.3: new high-speed USB device number 5 using dwc_otg
[79827.947579] usb 1-1.3: New USB device found, idVendor=1058, idProduct=1111
[79827.947611] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[79827.947628] usb 1-1.3: Product: My Book 1111
[79827.947641] usb 1-1.3: Manufacturer: Western Digital
[79827.947655] usb 1-1.3: SerialNumber: 574341563535323139373832
[79827.954851] scsi0 : usb-storage 1-1.3:1.0
[79828.953242] scsi 0:0:0:0: Direct-Access WD My Book 1111 1032 PQ: 0 ANSI: 4
[79828.954734] scsi 0:0:0:1: CD-ROM WD Virtual CD 1111 1032 PQ: 0 ANSI: 4
[79828.956757] scsi 0:0:0:2: Enclosure WD SES Device 1032 PQ: 0 ANSI: 4
[79828.966489] sd 0:0:0:0: [sda] 1952151552 512-byte logical blocks: (999 GB/930 GiB)
[79828.968510] sd 0:0:0:0: [sda] Write Protect is off
[79828.968547] sd 0:0:0:0: [sda] Mode Sense: 23 00 10 00
...
[79829.068725] sda: sda1
[79829.075284] sd 0:0:0:0: [sda] No Caching mode page present
[79829.095857] sd 0:0:0:0: [sda] Assuming drive cache: write through
[79829.102133] sd 0:0:0:0: [sda] Attached SCSI disk
The device that you inserted corresponds to the device file /dev/sda. Now let us see what partitions are there on this device
# fdisk -l /dev/sda
Disk /dev/sda: 999.5 GB, 999501594624 bytes
255 heads, 63 sectors/track, 121515 cylinders, total 1952151552 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0002ae3f
Device Boot Start End Blocks Id System
/dev/sda1 2048 952151551 976074752 7 HPFS/NTFS/exFAT
As you can see, there is only one partition on this disk. If you again run the mount command, you will see that this partition hasn’t yet been mounted. The mount command can be used for this purpose
# mount -t ntfs /dev/sda1 /var/disk1/
If you now rerun the mount command, you will see this line in the output
/dev/sda1 on /var/disk1 type fuseblk (rw,relatime,user_id=0,group_id=0,allow_other,blksize=4096)
Now, you can read/write from this disk by going to /var/disk1. One drawback of this mechanism is that you will have to do this manually everytime you restart the Pi. Assuming that you will have the disk always connected to your Pi, you can add the following entry to your /etc/fstab file
/dev/sda1 /var/disk1 ntfs defaults 0 0
/dev/sdb1 /var/disk2 ntfs defaults 0 0
I have another disk connected to the Pi and hence I add both entries to the file. Save the file and you will see that when you reboot your Pi, these disks will be ready to use.
Now you are ready to devise a file sharing/backup solution using one of the various possible mechanisms.
Programming¶
Fedora Linux for the Raspberry Pi already comes with Python, Ruby and Perl installed
# python --version
Python 2.7.3
# ruby --version
ruby 1.9.3p194 (2012-04-20 revision 35410) [armv5tel-linux
# perl --version
This is perl 5, version 14, subversion 2 (v5.14.2) built for arm-linux-thread-multi
Copyright 1987-2011, Larry Wall
Vi is installed
# vi --version
VIM - Vi IMproved 7.3 (2010 Aug 15, compiled Aug 29 2012 04:04:56)
Python¶
Getting to know your system using some of the standard library modules
# python
Python 2.7.3 (default, Jul 25 2012, 08:40:25)
[GCC 4.7.0 20120507 (Red Hat 4.7.0-5)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import platform
>>> platform.linux_distribution()
('Fedora remix', '17', 'Raspberrypi Fedora Remix')
>>> import os
>>> os.uname()
('Linux', 'raspberry', '3.2.27', '#1 PREEMPT Mon Oct 1 22:37:41 UTC 2012', 'armv6l')
>>> os.name
'posix'
>>> os.getlogin()
'root'
>>> os.getpid()
30378
>>> os.getppid()
29788
>>> os.pathsep
':'
>>> os.sep
'/'
>>> os.linesep
'\n'
>>> os.devnull
'/dev/null'
>>> import sys
>>> sys.platform
linux2
>>> sys.byteorder
'little
Use the subprocess module to access Linux commands
>>> import subprocess
>>> subprocess.call(['cat','/proc/cpuinfo'])
Processor : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS : 697.95
Features : swp half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xb76
CPU revision : 7
Hardware : BCM2708
Revision : 0003
Serial : 00000000f90cbb6b
0
>>> subprocess.call(['ifconfig'])
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.0.0.8 netmask 255.255.255.0 broadcast 10.0.0.255
inet6 fe80::ba27:ebff:fe0c:bb6b prefixlen 64 scopeid 0x20<link>
ether b8:27:eb:0c:bb:6b txqueuelen 1000 (Ethernet)
RX packets 44678 bytes 41925811 (39.9 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 27311 bytes 4467866 (4.2 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 16436
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 0 (Local Loopback)
RX packets 9366432 bytes 468467070 (446.7 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 9366432 bytes 468467070 (446.7 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
0
The pylinux package aims to provide a Python interface to the most common system information on a Linuxs system. Install it by cloning it from the project website and using the setup.py script to install the package:
# git clone https://github.com/amitsaha/pylinux.git
# python setup.py install
You can then use it, like so:
>>> import pylinux.pylinux as pylinux
>>> pylinux.distro_name()
'Fedora remix'
>>> pylinux.arch()
'armv6l'
>>> pylinux.freemem()
'44356 kB'
Install pip
# yum -y install python-pip
Web application using Flask¶
Flask can be used to create web applications on your Pi. Its simple, lightweight and really easy to get started.
Install Flask using
#yum -y install python-flask
Let us now write an example web application using Flask. Create a file app.py with the following contents
from flask import Flask
app = Flask(__name__)
@app.route("/")
def index():
return ''' <center><h1> Flask on Raspberry Pi </h1></center> \n
Time now ''' + time.ctime()
if __name__ == "__main__":
app.run(host='0.0.0.0',debug=True)
Now start the web application using:
# python app.py
You should see the following message
* Running on http://0.0.0.0:5000/
* Restarting with reloader
Now, if you visit the URL http://raspi-ip:5000 from your browser, you will see the following page (where raspi-ip is the IP address of your Raspberry Pi which you can find out as we saw earlier)
The @app.route(“/”) indicates that this is the function which will be called when you visit the URL: http://raspi-ip:5000. You could write your web application such that when you visit the URL: http://raspi-ip:5000/uptime, it gives you the time for which your Raspberry Pi has been switched on. Rewrite the app.py file as
import pylinux.pylinux as pylinux
from flask import Flask
import time
app = Flask(__name__)
@app.route("/uptime")
def uptime():
return 'Raspberry Pi up for %s hours' % str(pylinux.uptime())
@app.route("/")
def index():
return ''' <center><h1> Flask on Raspberry Pi </h1></center> \n
Time now ''' + time.ctime()
if __name__ == "__main__":
app.run(host='0.0.0.0',debug=True)
As you can see, we use the pylinux package to get the uptime in hours. Run the web application and you will see that when you visit the URL: http://raspi-ip:5000/uptime in your browser, you will get back the uptime for your Raspberry Pi.
The pylinux package includes a Flask web application which uses the package to display system statistics. It also uses jQuery and smoothie.js to display dynamic data. It can be found in the examples/flask_app directory.
Ruby¶
The Process class’s methods can be used to get useful information about the Ruby intepreter
irb(main):002:0> Process.pid()
=> 31224
irb(main):003:0> Process.ppid()
=> 29788
We can use Kernel’s system method to execute external Linux commands and get useful information
irb(main):001:0> system('whoami')
root
irb(main):013:0> system('uname -a')
Linux raspberry 3.2.27 #1 PREEMPT Mon Oct 1 22:37:41 UTC 2012 armv6l armv6l armv6l GNU/Linux
=> true
irb(main):002:0> system('cat /proc/cpuinfo')
Processor : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS : 697.95
Features : swp half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xb76
CPU revision : 7
Hardware : BCM2708
Revision : 0003
Serial : 00000000f90cbb6b
=> true
irb(main):003:0> system('ifconfig')
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.0.0.8 netmask 255.255.255.0 broadcast 10.0.0.255
inet6 fe80::ba27:ebff:fe0c:bb6b prefixlen 64 scopeid 0x20<link>
ether b8:27:eb:0c:bb:6b txqueuelen 1000 (Ethernet)
RX packets 71698 bytes 72360222 (69.0 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 40831 bytes 5926797 (5.6 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 16436
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 0 (Local Loopback)
RX packets 11999249 bytes 600570906 (572.7 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 11999249 bytes 600570906 (572.7 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
=> true
Fedora 17 comes with gem installed
# gem --version
1.8.24
Web application using Sinatra¶
CouchDB¶
Install couchdb and couchdb library for Python
# yum -y install couchdb
# pip-python install couchdb
Start Couchdb
# service couchdb start
Create a simple database and store data
>>> import couchdb
>>> couch = couchdb.Server('http://127.0.0.1:5984/')
>>> db = couch.create('test')
>>> doc={'name':'raspi'}
>>> db.save(doc)
('2a94bdde4f092c50be2ec8ab68000baa', '1-07a810f328653abedf230bb8321d3d4c')
>>> doc
{'_rev': '1-07a810f328653abedf230bb8321d3d4c', '_id': '2a94bdde4f092c50be2ec8ab68000baa', 'name': 'raspi'}
>>> db['2a94bdde4f092c50be2ec8ab68000baa']
<Document '2a94bdde4f092c50be2ec8ab68000baa'@'1-07a810f328653abedf230bb8321d3d4c' {'name': 'raspi'}>
GPIO Pins¶
The command line utility gpio can be used to acces the GPIO pins on the Raspberry Pi. This command is provided by the wiringpi package which is already installed on Fedora
# rpm -q wiringpi
wiringpi-1-4.rpfr17.armv5tel
To get the basic idea of accessing the GPIO pins using gpio, setup a simple LED circuit. Connect the anode of the LED to the GPIO pin 18 (pin 12 in real life) and the cathode to the Ground pin (6 in real life) via a resistor. The LED will not glow. We will now use gpio utlity to switch on the LED
# gpio -g mode 18 out
# gpio -g write 18 1
The LED should now be switched on. You can switch it off using
# gpio -g write 18 0
Next, we switch to Python for GPIO control using the RPI.GPIO package (http://pypi.python.org/pypi/RPi.GPIO). Install gcc and python-devel packages first and then install it using pip-python
# yum -y install gcc python-devel
# pip-python install RPi.GPIO
Use RPI.GPIO to switch on/off the LED
>>> import RPi.GPIO as GPIO
>>> GPIO.setmode(GPIO.BCM)
>>> GPIO.setup(18, GPIO.OUT)
>>> GPIO.output(18, GPIO.HIGH)
>>> GPIO.output(18, GPIO.LOW)
>>> GPIO.output(18, GPIO.HIGH)
Now, connect another LED such that its anode is connected to GPIO pin 23 (pin 14 in real life). Now that we have two LEDs with each capable of being in an ON or an OFF state, we can use them to display numbers (upto 3 in decimal) as their binary equivalent:
import sys
import RPi.GPIO as GPIO
# GPIO pins
pins = [18,23]
def setup_gpio():
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
for pin in pins:
GPIO.setup(pin, GPIO.OUT)
GPIO.output(pin, GPIO.LOW)
if __name__=='__main__':
if len(sys.argv) == 1:
print 'Usage: dec2bin_led.py <decimal integer>'
sys.exit()
dec = int(sys.argv[1])
if dec < 0 or dec > 2**len(pins)-1:
print 'Please enter a decimal integer between 0 and %s (both inclusive)' \
% str(2**len(pins)-1)
sys.exit()
binary = bin(dec).lstrip('0b')
setup_gpio()
for i,bit in enumerate(binary):
if bit=='1':
GPIO.output(pins[i], GPIO.HIGH)
else:
GPIO.output(pins[i], GPIO.LOW)
Run the program as follows
# python dec2bin_led.py 1
# python dec2bin_led.py 3
# python dec2bin_led.py 10
Please enter a decimal integer between 0 and 3 (both inclusive)
Depending on the decimal integer you enter, you will see none, one or both the LEDs glowing. You can also increase the number of LEDs and update the list of pins accordingly to increase the range of decimal input.
You could also consider writing a web application using Flask to control your LEDs via HTTP.
Half-baked Projects with Full Potential¶
Fedora Infrastructure Bus Scraper¶
Install python-zmq
# yum -y install python-zmq
A client program
#!/usr/bin/env python
'''
fedbus_client.py
Fedora Infrastructure Messaging Bus consumer
without using fedmsg.
Install python-zmq to use this.
Developed upon Ralph Bean's example code at
http://threebean.org/blog/zeromq-and-fedmsg-diy/
'''
import json
import pprint
import zmq
def listen_and_print():
# You can listen to stg at "tcp://stg.fedoraproject.org:9940"
endpoint = "tcp://hub.fedoraproject.org:9940"
# Listen to all messages being published
topic = 'org.fedoraproject.'
ctx = zmq.Context()
s = ctx.socket(zmq.SUB)
s.connect(endpoint)
s.setsockopt(zmq.SUBSCRIBE, topic)
poller = zmq.Poller()
poller.register(s, zmq.POLLIN)
while True:
evts = poller.poll() # This blocks until a message arrives
topic, msg = s.recv_multipart()
print topic, pprint.pformat(json.loads(msg))
if __name__ == "__main__":
listen_and_print()
When you run this program, you may have to wait, but will eventually see messages like
org.fedoraproject.prod.git.receive.jack-audio-connection-kit.master
{u'certificate':
u'LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUVSekNDQTdD
.....
.....
Z0
u'i': 1,
u'msg': {u'commit': {u'branch': u'master',
u'email': u'brendan.jones.it@gmail.com',
u'message': u'Add audio group in README dropped in merging.\n',
u'name': u'Brendan Jones',
u'rev': u'b81b6f46a94c9603c5f1b199f22ec7d2589bfe07',
u'stats': {u'files': {u'jack-audio-connection-kit-README.Fedora': {u'deletions': 1,
u'insertions': 1,
u'lines': 2}},
u'total': {u'deletions': 1,
u'files': 1,
u'insertions': 1,
u'lines': 2}},
u'summary': u'Add audio group in README dropped in merging.',
u'username': u'bsjones'}},
u'signature': u'vNqmuPiwvVSEQGqL3Q4dlMGQ1VfSJmaB5yTjCg3K0M+GVgvvZVX7D1LbZjKeYpM2zyd893px4LDF\nt7kustfGPXFfN156TMtnoLtLNENKoSmbOqmD5aDWJclgdfh/WQTqAH9QnpbFX93PAIupLeKEcM16\nUIweYYhtj/DCEB85pZ0=\n',
u'timestamp': 1353227420.312382,
u'topic': u'org.fedoraproject.prod.git.receive.jack-audio-connection-kit.master'}
Zer0mq Broadcaster¶
Next Things to do¶
Miscellaneous¶
Source for the book¶
The book and the source is available here under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported license. See LICENSE file for the complete description.
Very much a work under construction. Comments/suggestions welcome.