Description: With the widespread adoption of containerization technology, an increasing number of applications are deployed in containers. Sometimes, in production environments, we may need to capture packets on a container to understand its network communication and troubleshoot communication anomalies.
Here, since the program is running in a Kubernetes Pod container, and the containers supporting the business often do not have packet capture commands installed, capturing packets on Pods can often be a headache.
To solve this problem, we can capture packets on Pod containers in several ways.
Description: This is the first method that beginners often think of, and of course, it is the simplest way, which is to install the command in the Pod container and then use the command directly to capture packets.
However, as commands are often not installed in Pod containers, installing tcpdump increases the image size, and without an external network connection, it is not possible to install online.
Description: This method is frequently used in actual production environments. By locating the host (Node) where the Pod container is running and sniffing on the network interface index on the node where the Pod is located, you can capture packets and then analyze them using tools.
The nsenter command is a command that can run a specified program under the command space of a specified process. Using it, we can directly use the tcpdump command in the Pod container to capture packets.
Description: ksniff is a kubectl plugin that uses tcpdump and Wireshark to initiate remote packet capture on any Pod in the Kubernetes cluster (this is the method recommended by the author).