LXD run command in all running containers, optionally in parallel

lxc-exec-all.sh

#!/bin/bash

#
# Run command in all running containers
# Usage: $ ./lxc-exec-all.sh apt update && apt upgrade
#
# To run in all in parallel, put '*' as the first argument.
#

if "$1"=="*" then
    shift
    # Run in parallel
    sudo lxc list volatile.last_state.power=RUNNING -c n --format csv | \
        parallel -j $(nproc) -- sudo lxc exec '{}' -- "$@" || exit
else
    # Sequential
    for container in $(sudo lxc list volatile.last_state.power=RUNNING -c n --format csv); do
        sudo lxc exec "$container" -- "$@"
    done
fi