debug-kernel.md

Get cc-runtime Kernel logs

The cc-runtime launches a virtual machine when a new pod is created. This virtual machine (VM) uses a custom kernel inside the VM.

The kernel boot logs are disabled by default. However these logs may be desired when the kernel is customized by the end user, or if the virtual machine boot fails due to the kernel.

To provide a debug log of the kernel boot, Clear Containers supports an option to enable kernel boot logs using the configuration file.

1. Enable kernel boot messages

   Set the enable_debug= option in the [proxy.cc] section to true, which assumes a standard configuration file path:

   $ sudo awk '{if (/^\[proxy\.cc\]/) {got=1}; if (got == 1 && /^#enable_debug/) {print "enable_debug = true"; got=0; next; } else {print}}' /usr/share/defaults/clear-containers/configuration.toml
   

2. Run a container to generate the logs

   $ sudo docker run -ti busybox true
   

3. Filter the kernel boot logs from the cc-proxy logs

   The cc-proxy logs show the sources of its collated information. To see the kernel boot logs, filter cc-proxy logs by the QEMU serial console, excluding the agent messages. The QEMU serial console is represented by source=qemu.

   $ sudo journalctl -t cc-proxy | grep source=qemu | egrep -v '\<cc-agent\>'
   

   To extract all logs entries for a particular container:

   $ sudo sudo journalctl -t cc-proxy | grep source=qemu | grep vm=CONTAINER_ID | egrep -v '\<cc-agent\>'