Hybris-boot offers a telnet service that you can use to debug the very early init of your port. This service will be exposed if the Halium system has failed to boot for any reason.
Determining if this is needed¶
While bringing the USB network interface up, the boot image will write a few debug messages. These debug messages are communicated via a clever hack of resetting the serial number of the usb connection.
The steps in detail are:
Execute this command to watch the changes in the usb serial number:
while : ; do lsusb -v 2>/dev/null | grep -Ee 'iSerial +[0-9]+ +[^ ]' ; done | uniq
Boot your newly built image
Watch the output of the lsusb command above. It will put out lines like this:
iSerial 3 01234567 iSerial 3 Mer Debug setting up (DONE_SWITCH=no) iSerial 3 Mer Debug telnet on port 23 on usb0 192.168.2.15 - also running udhcpd
If you get a line similar to the last two above, Telnet is running. Continue to the next section to debug it.
If you instead get the line
GNU/Linux devices on rndis0 10.15.19.82, the system has booted successfully. Move to Logging in to continue your debugging.
Debugging via telnet¶
- Determine the name of the usb network device on your desktop:
dmesg | tail. You’re looking for a line similar to this:
[ 1234.123456] rndis_host 1-7:1.0 enp0s20f0u7: renamed from usb0
In this example shown above,
enp0s20f0u7is the usb network device name. Use this for the USBNETWORK below
Check if the usb network device has a MAC address assigned:
$ ip address show dev USBNETWORK 6: USBNETWORK: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000 link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
If it shows the link/ether address
00:00:00:00:00:00as shown above, you will have to manually assign the MAC address:
ip link set USBNETWORK address 02:01:02:03:04:08
You can set any MAC address you want, it just needs to be a valid MAC address.
Configure usb networking:
sudo ip address add 192.168.2.1 dev USBNETWORK ip address show dev USBNETWORK sudo ip route add 192.168.2.15 dev USBNETWORK ping -c 2 192.168.2.15
Connect with telnet:
Now you have terminal access to the system running from initrd.
If telnet is never exposed¶
If the device simply reboots when trying to boot and does not bring up telnet, you may build and use the
hybris-recovery.img file to attempt to force a shell to come up. To do this, set up your build tree and issue the following command:
The file will be in the standard $OUTDIR. Simply flash it in the same way you did for
There are several cases in which telnet will not be exposed, such as when the device fails to load the kernel or initramfs, or when an in-kernel driver decides to cause a kernel panic very early. In this case, the phone will almost immediately reboot when it starts, even when using
hybris-recovery. To see why this is happening, you may be able to read the previous boot’s kernel message buffer. Please have that ready if you contact us for help.