Debug

Debugging slim docker images running in a Kubernetes environment can be painful. It is often lacking tools such as `ping, dig or curl.

This page captures some alternative commands to do trivial operations.

DNS Lookup

DNS resolution.

Using curl:

$ curl --trace-ascii - https://google.com
== Info: Host google.com:443 was resolved.
== Info: IPv6: 2a00:1450:400a:804::200e
== Info: IPv4: 142.250.178.206
== Info:   Trying 142.250.178.206:443...
== Info: Connected to google.com (142.250.178.206) port 443
...

Using python:

$ python3
import socket
print(socket.getaddrinfo('google.com', 443))

Netcat / nc

Test if a port is open

Using curl:

$ curl --max-time 1 --trace-ascii - google.com:444
== Info: Host google.com:444 was resolved.
== Info: IPv6: 2a00:1450:400a:808::200e
== Info: IPv4: 142.250.178.206
== Info:   Trying 142.250.178.206:444...
== Info:   Trying [2a00:1450:400a:808::200e]:444...
== Info: Immediate connect fail for 2a00:1450:400a:808::200e: Network is unreachable
== Info: Connection timed out after 1001 milliseconds
== Info: Closing connection
curl: (28) Connection timed out after 1001 milliseconds