Setting up the networking

OK, now our ESPRESSObin is ready to execute our code and our drivers! However, before ending this section, let's take a look at the networking configuration since it can be further useful to log in to the board using an SSH connection or just to copy files from/to the board quickly (even if we can remove the microSD and then copy our files from the host PC directly):

1. Taking a look at available network interfaces on the ESPRESSObin, we see the following:

# ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT
 group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group
 default qlen 532
    link/ether 3a:ac:9b:44:90:e9 brd ff:ff:ff:ff:ff:ff
3: wan@eth0: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN mode DE
FAULT group default qlen 1000
    link/ether 3a:ac:9b:44:90:e9 brd ff:ff:ff:ff:ff:ff
4: lan0@eth0: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN mode D
EFAULT group default qlen 1000
    link/ether 3a:ac:9b:44:90:e9 brd ff:ff:ff:ff:ff:ff
5: lan1@eth0: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN mode D
EFAULT group default qlen 1000
    link/ether 3a:ac:9b:44:90:e9 brd ff:ff:ff:ff:ff:ff

The eth0 interface is the one that connects the CPU with the Ethernet switch while the wan, lan0, and lan1 interfaces are the ones where we can physically connect our Ethernet cables (note that the system calls them wan@eth0, lan0@eth0, and lan1@eth1 just to underline the fact they are slaves of eth0). Following is a photograph of the ESPRESSObin, where we can see each Ethernet port with its label:

1. Despite their names, all ports are equivalent so connect the Ethernet cable into one port (I'm going to use wan) and then enable it after eth0, as follows:

# ip link set eth0 up
mvneta d0030000.ethernet eth0: configuring for fixed/rgmii-id link mode
mvneta d0030000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
# ip link set wan up 
mv88e6085 d0032004.mdio-mii:01 wan: configuring for phy/ link mode
mv88e6085 d0032004.mdio-mii:01 wan: Link is Up - 100Mbps/Full - flow control rx/tx

1. Now, we can manually set an IP address or we can ask our DHCP server whatever we need to surf the internet with the dhclient command:

# dhclient wan

Here is my network configuration:

# ip addr show wan
3: wan@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP g
roup default qlen 1000
    link/ether 9e:9f:6b:5c:cf:fc brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.100/24 brd 192.168.0.255 scope global wan
       valid_lft forever preferred_lft forever

1. Now, we're ready to install new software or to try to establish an SSH connection to the ESPRESSObin; to do so, let's verify that we have the following SSH server's configuration in the/etc/ssh/sshd_config file:

# grep 'PermitRootLogin yes' /etc/ssh/sshd_config
PermitRootLogin yes

1. If we get no output, we cannot log in as root into our ESPRESSObin, so we must change the PermitRootLogin setting to yes and then restart the daemon:

# /etc/init.d/ssh restart

Restarting ssh (via systemctl): ssh.service.

1. Now, on the host PC, we can try the login via SSH, as follows:

$ ssh root@192.168.0.100
root@192.168.0.100's password: 
Linux espressobin 4.18.0 #2 SMP PREEMPT Sun Jan 13 13:05:03 CET 2019 aarch64

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the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Thu Nov 3 17:16:59 2016
-bash: warning: setlocale: LC_ALL: cannot change locale (en_GB.UTF-8)