podns

Run arbitrary cmd in pod namespace

use-case

• When you don't want to add your tools to the pod but they're available on the host.
• When you just want to inspect a running process but don't feel like jumping through the latest hoops of the distributed container orchestration maze.
• When you need sudo power but the container doesn't run as root.

requirements

• bash and kubectl on local host
• docker, nsenter, ssh access to-, and sudoer on remote host
• Any command you want to run must be available on the remote host

usage

$ ./podns.sh <pod> <remote_user> [<cmd>]

pod and remote_user are required. cmd is optional - omit to get a remote shell on the host tied to the pod namespace. The pod should probably be in a running state. if cmd is set it is run with sudo. Use @PID to inject container pid in cmd. Make sure to put a long cmd in quotes.

examples

List all network connections

# redirect stderr to ignore chatter about UID
$ ./podns.sh pod user "lsof -anP -i 2> /dev/null"

Get a shell

$ ./podns.sh pod user

useful commands

# Poll every 5s for your server to be connected to redis
lsof -anP -i:6379 -r 5
# List servers listening
lsof -anP -i tcp | grep -i listen
# Check http end point
curl localhost:5000/health -sik
# Run a trace on read syscalls
strace -e trace=read -t -s 128 -p @PID
# Grab mem usage
ps -v -p @PID

filter

Use filters to filter output of a remote command by piping to it.

# get number of websockets connected to <port>
$ ./podns.sh pod user "lsof -nP -i 2> /dev/null" | go run filter/ws.go <port>

kubectl plugin

podns can be used as a kubectl plugin and invoked with kubectl podns ...args. Just copy the script to somewhere in your $PATH and rename it to kubectl-podns.

$ cp -iv podns.sh /usr/local/bin/kubectl-podns

todos

• if $1 is --help print usage and exit
• validate output
• put echo steps behind debug flag
• shell option
• arg REMOTE_USER
• filters
• arg cmd
• echo to stderr so pipes work
• add strace example
• allow multiple pids or dc