TS-4900 Debian Sections
Debian is a community run Linux distribution. Debian provides tens of thousands of precompiled applications and services. This distribution is known for stability and large community providing support and documentation. This distribution does not include the same support as Yocto for the GPU. OpenGL ES, Gstreamer, or OpenCL are not supported in Debian. The framebuffer is supported so 2D applications will still run well. Debian is also very well suited for headless applications.
Getting Started with Debian
While the Yocto distribution provides a more powerful cross compiler environment and better support for the graphics in the i.MX6, the Debian image provides a much larger community and prebuilt packages for armhf.
To write this to an SD card, first partition the SD card to have one large ext4 partition. See the guide here for more information. Once it is formatted, extract this tar with:
# Assuming your SD card is /dev/sdc with one partition
mkfs.ext4 /dev/sdc1
mkdir /mnt/sd/
sudo mount /dev/sdc1 /mnt/sd/
sudo tar xjf debian-armhf-wheezy-20150326.tar.bz2 -C /mnt/sd
sudo umount /mnt/sd
sync
Debian Networking
From almost any Linux system you can use "ip" or the ifconfig/route commands to initially set up the network. To configure the network interface manually you can use the same set of commands in the initramfs or Debian.
# Bring up the CPU network interface
ifconfig eth0 up
# Or if you're on a baseboard with a second ethernet port, you can use that as:
ifconfig eth1 up
# Set an ip address (assumes 255.255.255.0 subnet mask)
ifconfig eth0 192.168.0.50
# Set a specific subnet
ifconfig eth0 192.168.0.50 netmask 255.255.0.0
# Configure your route. This is the server that provides your internet connection.
route add default gw 192.168.0.1
# Edit /etc/resolv.conf for your DNS server
echo "nameserver 192.168.0.1" > /etc/resolv.conf
Most commonly networks will offer DHCP which can be set up with one command:
Configure DHCP in Debian:
# To setup the default CPU ethernet port
dhclient eth0
# Or if you're on a baseboard with a second ethernet port, you can use that as:
dhclient eth1
# You can configure all ethernet ports for a dhcp response with
dhclient
Configure DHCP in the initrd:
udhcpc -i eth0
# Or if you're on a baseboard with a second ethernet port, you can use that as:
udhcpc -i eth1
To make your network settings take effect on startup in Debian, edit /etc/network/interfaces:
# Used by ifup(8) and ifdown(8). See the interfaces(5) manpage or
# /usr/share/doc/ifupdown/examples for more information.
# We always want the loopback interface.
#
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet static
address 192.168.0.50
netmask 255.255.255.0
gateway 192.168.0.1
auto eth1
iface eth1 inet dhcp
| Note: | During Debian's startup it will assign the interfaces eth0 and eth1 to the detected mac addresses in /etc/udev/rules.d/70-persistent-net.rules. If the system is imaged while this file exists it will assign the new interfaces as eth1 and eth2. This file is generated automatically on startup, and should be removed before your first software image is created. The initrd network configuration does not use this file. |
In this example eth0 is a static configuration and eth1 receives its configuration from the DHCP server. For more information on network configuration in Debian see their documentation here.
Debian Wheezy WIFI Client
Scan for a network
ifconfig wlan0 up
# Scan for available networks
iwlist wlan0 scan
In this case I'm connecting to "default" which is an open network:
Cell 03 - Address: c0:ff:ee:c0:ff:ee
Mode:Managed
ESSID:"default"
Channel:2
Encryption key:off
Bit Rates:9 Mb/s
To connect to this open network:
iwconfig wlan0 essid "default"
You can use the iwconfig command to determine if you have authenticated to an access point. Before connecting it will show something similar to this:
# iwconfig wlan0
wlan0 IEEE 802.11bgn ESSID:"default"
Mode:Managed Frequency:2.417 GHz Access Point: c0:ff:ee:c0:ff:ee
Bit Rate=1 Mb/s Tx-Power=20 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=70/70 Signal level=-34 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
If you are connecting using WEP, you will need to define a network key:
iwconfig wlan0 essid "default" key "yourpassword"
If you are connecting to WPA you will need to use wpa_passphrase and wpa_supplicant:
wpa_passphrase the_essid the_password >> /etc/wpa_supplicant.conf
Now that you have the configuration file, you will need to restart the wpa_supplicant daemon:
ifdown wlan0 && ifup wlan0
The wpa_supplicant is started on ifup and /etc/network/interfaces includes the configuration to automatically use dhcp. It must be changed to automatically bring up the interface on startup:
# Wireless interfaces
auto wlan0 # this needs to be added to automatically ifup the interface
iface wlan0 inet dhcp
wireless_mode managed
wireless_essid any
wpa-driver wext
wpa-conf /etc/wpa_supplicant.conf
## If you are using a static ip instead:
#iface wlan0 inet static
# wireless_mode managed
# wireless_essid any
# wpa-driver wext
# wpa-conf /etc/wpa_supplicant.conf
# address 192.168.0.50
# netmask 255.255.255.0
# gateway 192.168.0.1
Debian Wheezy WIFI Access Point
First, hostapd needs to be installed in order to manage the access point on the device:
apt-get update && apt-get install hostapd -y
| Note: | The install process will start an unconfigured hostapd process. This process must be killed and restarted before a new hostapd.conf will take effect. |
Edit /etc/hostapd/hostapd.conf to include the following lines:
interface=wlan0 driver=nl80211 ssid=YourAPName channel=1
| Note: | Refer to the kernel's hostapd documentation for more wireless configuration options. |
To start the access point launch hostapd:
hostapd /etc/hostapd/hostapd.conf &
This will start up an access point that can be detected by WIFI clients. A DHCP server will likely be desired to assign IP addresses. Refer to Debian's documentation for more details on DHCP configuration.
Debian Installing New Software
Debian provides the apt-get system which manages pre-built applications. Before packages can be installed, the list of package versions and locations needs to be updated. This assumes the device has a valid network connection to the internet.
Debian Wheezy has been moved to archive status, this requires an update of /etc/apt/sources.list to contain only the following lines:
deb http://archive.debian.org/debian wheezy main non-free deb-src http://archive.debian.org/debian wheezy main non-free
apt-get update
apt-get install --allow-unauthenticated debian-archive-keyring
apt-get update
For example, lets say you wanted to install openjdk for Java support. You can use the apt-cache command to search the local cache of Debian's packages.
<user>@<hostname>:~# apt-cache search openjdk icedtea-6-jre-cacao - Alternative JVM for OpenJDK, using Cacao icedtea6-plugin - web browser plugin based on OpenJDK and IcedTea to execute Java applets openjdk-6-dbg - Java runtime based on OpenJDK (debugging symbols) openjdk-6-demo - Java runtime based on OpenJDK (demos and examples) openjdk-6-doc - OpenJDK Development Kit (JDK) documentation openjdk-6-jdk - OpenJDK Development Kit (JDK) openjdk-6-jre-headless - OpenJDK Java runtime, using Hotspot Zero (headless) openjdk-6-jre-lib - OpenJDK Java runtime (architecture independent libraries) openjdk-6-jre-zero - Alternative JVM for OpenJDK, using Zero/Shark openjdk-6-jre - OpenJDK Java runtime, using Hotspot Zero openjdk-6-source - OpenJDK Development Kit (JDK) source files openoffice.org - office productivity suite freemind - Java Program for creating and viewing Mindmaps default-jdk-doc - Standard Java or Java compatible Development Kit (documentation) default-jdk - Standard Java or Java compatible Development Kit default-jre-headless - Standard Java or Java compatible Runtime (headless) default-jre - Standard Java or Java compatible Runtime
In this case you will likely want openjdk-6-jre to provide a runtime environment, and possibly openjdk-6-jdk to provide a development environment. You can often find the names of packages from Debian's wiki or from just searching on google as well.
Once you have the package name you can use apt-get to install the package and any dependencies. This assumes you have a network connection to the internet.
apt-get install openjdk-6-jre
# You can also chain packages to be installed
apt-get install openjdk-6-jre nano vim mplayer
For more information on using apt-get refer to Debian's documentation here.
Debian Setting up SSH
On our boards we include the Debian package for openssh-server, but we remove the automatically generated keys for security reasons. To regenerate these keys:
dpkg-reconfigure openssh-server
Make sure your board is configured properly on the network, and set a password for your remote user. SSH will not allow remote connections without a password or a shared key.
| Note: | Setting up a password for root is only feasible on the uSD image. |
passwd root
You should now be able to connect from a remote Linux or OSX system using "ssh" or from Windows using a client such as putty.
| Note: | If your intended application does not have a DNS source on the target network, it can save login time to add "UseDNS no" in /etc/ssh/sshd_config. |
Debian Starting Automatically
From Debian the most straightforward way to add your application to startup is to create a startup script. This is an example simple startup script that will toggle the red led on during startup, and off during shutdown. In this case I'll name the file customstartup, but you can replace this with your application name as well.
Edit the file /etc/init.d/customstartup to contain this:
#! /bin/sh
# /etc/init.d/customstartup
case "$1" in
start)
/path/to/your/application
## If you are launching a daemon or other long running processes
## this should be started with
# nohup /usr/local/bin/yourdaemon &
;;
stop)
# if you have anything that needs to run on shutdown
/path/to/your/shutdown/scripts
;;
*)
echo "Usage: customstartup start|stop" >&2
exit 3
;;
esac
exit 0
| Note: | The $PATH variable is not set up by default in init scripts so this will either need to be done manually or the full path to your application must be included. |
To make this run during startup and shutdown:
update-rc.d customstartup defaults
To manually start and stop the script:
/etc/init.d/customstartup start
/etc/init.d/customstartup stop