On this page we configure the network settings of the RPi and setup the required SSH connectivity. When completed you should be able to access the RPi from the XCS with the use of SSH keys via either WiFi and/or USB.
Detect SDCard & find largest partition (the RPi filesystem)
XCS~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 25G 0 disk
├─sda1 8:1 0 487M 0 part /boot
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 24.5G 0 part
├─XCS--rpizero--vg-root 252:0 0 20.5G 0 lvm /
└─XCS--rpizero--vg-swap_1 252:1 0 4G 0 lvm [SWAP]
sdb 8:16 1 7.3G 0 disk
├─sdb1 8:17 1 63M 0 part <=== Smallest partition (boot)
└─sdb2 8:18 1 7.3G 0 part <=== Largest partition
sr0 11:0 1 55.7M 0 rom
Mount SDCard
XCS~$ sudo mount /dev/sdb2 $XC_RPI_MNT
If required, configure the ip-address handling on the RPi. For example, you can use a static ip-address (e.g. 192.168.1.100) as a fallback when DHCP fails:
XCS~$ sudo nano $XC_RPI_MNT/etc/dhcpcd.conf
Edit following lines as required for your setup and add these to the bottom of dhcpcd.conf:
profile static_ip
static ip_address=192.168.1.100/24
static routers=192.168.1.1
static domain_name_servers=192.168.1.1
interface wlan0
fallback static_ip
More information on how to manage (multiple) (static) networks be found here.
“/24” indicates a used subnet mask of “255.255.255.0”. You can change it to “/16” (“255.255.0.0”) or “/8” (“255.0.0.0”) as you require.
Install wpa_passphrase for secure password handling for Wifi setup
XCS~$ sudo apt-get install wpasupplicant
Create secure network-credentials
XCS~$ wpa_passphrase "<network-ssid>"
# reading passphrase from stdin
<type-here-your-password>
network={
ssid="<network-ssid>"
#psk="<password>"
psk=<32-byte-hexadecimal-encrypted-password>
}
Setup WiFi
XCS~$ sudo nano $XC_RPI_MNT/etc/wpa_supplicant/wpa_supplicant.conf
Add the required wpa_passphrase-results to this file. The order equals the connection order. So in this example, network1 is first tried for setting up a connection, when failing, network2 is tested.
network={
ssid="<network2-ssid>"
psk="<32-byte-hexadecimal-encrypted-password-of-network1>"
}
network={
ssid="<network2-ssid>"
psk="<32-byte-hexadecimal-encrypted-password-of-network2>"
}
To setup SSH we need access to the boot (or smallest) partition on the SDCard. As such, we first need to unmount the large partition and connect the smallest.
XCS~$ sudo umount $XC_RPI_MNT
XCS~$ sudo mount /dev/sdb1 $XC_RPI_MNT
Add ssh file and we are done.
XCS~$ sudo touch $XC_RPI_MNT/ssh
XCS~$ sudo umount $XC_RPI_MNT
By default, the hostname of a RPi is raspberrypi, hence the RPi can be accessed via the dns raspberrypi.local. As multiple RPi’s might be active in the environment, connection issues may occur. The following steps show how to change the hostname.
Mount the largest partition of the SDCard in the XCS.
XCS~$ sudo mount /dev/sdb2 $XC_RPI_MNT
Edit hostname
XCS~$ sudo nano $XC_RPI_MNT/etc/hostname
raspberrypi in e.g. rpizwEdit hosts
XCS~$ sudo nano $XC_RPI_MNT/etc/hosts
127.0.0.1 raspberrypi in e.g. 127.0.0.1 rpizw.
The hostname in
etc/hostsshould equal the name written down inetc/hostnamepreviously. The result might look like:
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
127.0.0.1 rpizw
Finish setup by unmounting the mounted partition
XCS~$ sudo umount $XC_RPI_MNT
Hooray! We can now finally boot the RPi. But before we can continue our quest to cross-compiling, we need to do some RPi-maintenance.
Note: While it is advisable, you can skip this (re)boot step and continue adjusting settings before you actually reboot. Nonetheless, you eventually need to do these steps!
SSH to the RPi (use hostname or ip-address if known)
XCS~$ ssh pi@rpizw.local
Expand filesystem to use full size of SDCard & reboot
RPI~$ sudo raspi-config --expand-rootfs
RPI~$ sudo reboot now
After reboot, connect again & update RPi
XCS~$ ssh pi@rpizw.local
RPI~$ sudo apt-get update
RPI~$ sudo apt-get dist-upgrade
During update, you might encounter errors like
E: Repository 'http://raspbian.raspberrypi.org/raspbian buster InRelease' changed its 'Suite' value from 'stable' to 'oldstable' N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
To fix these errors, type in the following and retry:
sudo apt-get update --allow-releaseinfo-change
Currently, you need to enter your password each time you connect to the RPi. With the use of SSH-keys, we can automate this process.
Generate ssh-keys in the XCS.
XCS~$ cd ~/.ssh
XCS~$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/pi/.ssh/id_rsa): rpizero_rsa
Enter passphrase (empty for no passphrase): <empty>
Enter same passphrase again: <empty>
Your identification has been saved in rpizero_rsa.
Your public key has been saved in rpizero_rsa.pub.
...
Optionally you can choose a different rsa-name (required if you are planning to use multiple keys for different systems) and set a passphrase (increasing security). In my setup I left the passphrase empty (just hitting enter).
Set correct permissions of the key-set
XCS~$ chmod 700 rpizero_rsa rpizero_rsa.pub
Send a copy of the public key to the RPi so the RPi can verify the automated connection upon request.
XCS~$ cat ~/.ssh/rpizero_rsa.pub | ssh pi@rpizw.local "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"
This step can also be performed locally when the SD card is connected to XCS:
XCS~$ sudo mount /dev/sdb2 $XC_RPI_MNT
XCS~$ mkdir -p $XC_RPI_MNT/home/pi/.ssh
XCS~$ cat ~/.ssh/rpizero_rsa.pub >> $XC_RPI_MNT/home/pi/.ssh/authorized_keys
XCS~$ sudo umount $XC_RPI_MNT
Setup ssh connection in ssh_config so we can login by only using a reference
XCS~$ sudo nano /etc/ssh/ssh_config
Depending on the configuration of dhcpcd.conf on the RPi, add the following lines:
#connect via static ip
Host rpizero
HostName 192.168.1.100
IdentityFile ~/.ssh/rpizero_rsa
User pi
Port 22
# connect via hostname
Host rpizero-local
HostName rpizw.local
IdentityFile ~/.ssh/rpizero_rsa
User pi
Port 22
You can edit the
Host XXlines to any reference you seem fit. This reference is only used in the SSH callssh XXto login to the defined setup.
Allow bash to invoke the configuration upon a ssh-call
XCS~$ ssh-agent bash
XCS~$ ssh-add /home/pi/.ssh/rpizero_rsa
Identity added: /home/pi/.ssh/rpizero_rsa (/home/pi/.ssh/rpizero_rsa)
Test connection:
XCS~$ ssh rpizero-local
You should now be logged in onto the RPi via SSH, without entering your password.
For synchronisation with our cross-compile environment the setup required root access over SSH.
Login to the RPi the enable root.
XCS~$ ssh rpizero-local
Setup root-password.
RPI~$ sudo passwd root
New password:
Retype new password:
passwd: password updated successfully
IMPORTANT: the given password should equal the password for the user
pi!!
Enable root-login
RPI~$ sudo nano /etc/ssh/sshd_config
set PermitRootLogin XXXX to PermitRootLogin yes.
Restart ssh service and quit connection
RPI~$ sudo service ssh restart
RPI~$ exit
Configure ssh connection in ssh_config
XCS~$ sudo nano /etc/ssh/ssh_config
Depending on the configuration of dhcpcd.conf on the RPi, add the following lines:
#connect via static ip
Host rpizero-root
HostName 192.168.1.100
IdentityFile ~/.ssh/rpizero_rsa
User root
Port 22
# connect via hostname
Host rpizero-local-root
HostName rpizw.local
IdentityFile ~/.ssh/rpizero_rsa
User root
Port 22
You can edit the
Host XXlines to any reference you seem fit. This reference is only used in the SSH callssh XXto login to the defined setup.
Send a copy of the ssh-keys for the root user to the RPi:
XCS~$ cat ~/.ssh/rpizero_rsa.pub | ssh root@rpizw.local "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"
Test connection:
XCS~$ ssh rpizero-local-root
You should now be logged in onto the RPi via ssh as root without entering your password.
If your RPi will always be accessed via WiFi, this step can be skipped. If not: in this step we enable SSH access over the USB connector, to ensure we can connect to the RPi in environments without network connectivity.
If the RPi is running, shutdown, remove SDCard, connect the SDCard to the XCS and mount the smallest partition.
$RPI~$ sudo shutdown now
XCS~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 25G 0 disk
├─sda1 8:1 0 487M 0 part /boot
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 24.5G 0 part
├─XCS--rpizero--vg-root 252:0 0 20.5G 0 lvm /
└─XCS--rpizero--vg-swap_1 252:1 0 4G 0 lvm [SWAP]
sdb 8:16 1 7.3G 0 disk
├─sdb1 8:17 1 63M 0 part <=== Smallest partition
└─sdb2 8:18 1 7.3G 0 part
sr0 11:0 1 55.7M 0 rom
XCS~$ sudo mount /dev/sdb1 $XC_RPI_MNT
Update the configuration file
XCS~$ sudo nano $XC_RPI_MNT/config.txt
Add the following lines at the bottom of the file:
#allow ssh over usb
dtoverlay=dwc2
Update cmdline.txt
XCS~$ sudo nano $XC_RPI_MNT/cmdline.txt
Add modules-load=dwc2,g_ether right after rootwait. Because this file is very sensitive to enter, space or tabs, make sure you do not add additional characters to it. After editing the final file might look like:
dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait modules-load=dwc2,g_ether
Mount largest partition
XCS~$ sudo umount $XC_RPI_MNT
XCS~$ sudo mount /dev/sdb2 $XC_RPI_MNT
Setup static fallback when DHCP is not providing an IP.
XCS~$ sudo nano $XC_RPI_MNT/etc/dhcpcd.conf
Add the following lines to dhcpcd.conf:
interface usb0
fallback static_ip
Note that this example is using the static profile, configured earlier in this guide. You could setup a different IP address as shown before. If you copied the settings from this guide,
dhcpcd.confshould read: ``` profile static_ip static ip_address=192.168.1.100/24 static routers=192.168.1.1 static domain_name_servers=192.168.1.1
interface wlan0 fallback static_ip
interface usb0 fallback static_ip ```
Unmount SDCard
XCS~$ sudo umount $XC_RPI_MNT
Bootup the RPi with one end of the USB cable connected to your machine and the other end to the USB port of the device. Make sure that in case of the Raspberry Pi Zero you do not connect the USB cable with with the PWR port as this port does not support the USB protocol.
HOST~$ (OSX):
You should now be able to connect with the RPi via the set IP address, hostname or SSH-config
XCS~$ ssh pi@192.168.1.100
XCS~$ ssh rpizw.local
XCS~$ ssh rpizero-local
ifconfig on the RPi might look like:
RPI~$ ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
usb0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.100 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 fe80::66a1:27c3:5dc2:b760 prefixlen 64 scopeid 0x20<link>
ether 4a:3a:94:3c:c8:e5 txqueuelen 1000 (Ethernet)
RX packets 420 bytes 76163 (74.3 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 174 bytes 17378 (16.9 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.2.181 netmask 255.255.255.0 broadcast 192.168.2.255
inet6 fe80::95d0:e9ed:d380:bb04 prefixlen 64 scopeid 0x20<link>
ether b8:27:eb:68:cc:d8 txqueuelen 1000 (Ethernet)
RX packets 1151 bytes 195875 (191.2 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 353 bytes 52663 (51.4 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
Note that in this example
wlan0is configured by DHCP, whereasusb0has been initialised with the static setup.
You can either setup some peripherals such as i2c devices or the camera or start to setup the cross-compilation environment.