Note: A good deal of the functionality provided here is now available via iovisor/kubectl-trace. Check it out!

A towel, it says, is about the most massively useful thing an interstellar hitchhiker can have.

-- Douglas Adams

Getting Started Tutorial

If you are new to linux tracing I highly recommend you read our Getting Started Tutorial. It will walk you through step-by-step how to get started tracing your programs running in a GKE cluster.

Installation

go get github.com/jasonkeene/towel/...

Usage

# apply the towel daemonset
kubectl towel apply

# exec onto the towel for a given pod
kubectl towel exec nginx
kubectl towel exec -l app=nginx --field-selector spec.nodeName=node-1

# delete the towel daemonset
kubectl towel delete

Things You Can Do with the Towel

Run bpftrace

bpftrace -l
bpftrace -e 'BEGIN { printf("Hello, World!\n"); }'

Run BCC Tools

opensnoop
tcpaccept
tcpconnect

Write Your Own BCC Tools

python -c '

from bcc import BPF
BPF(text=r"""
int kprobe__sys_clone(void *ctx)
{
    bpf_trace_printk("Hello, World!\n");
    return 0;
}
""").trace_print()

'

Talk to the Docker Daemon

docker ps

Downloading GKE Kernel Source

You might run into situations where you need the kernel source. If you are running the chromium OS image on GKE you can use the following:

download-chromium-os-kernel-source

It will print out the environment variables you need to export to allow BCC and bpftrace to know where to look for the sources.