An hacky way to replace K8S configmap from file, optionally signaling a deployment's containers once done. Be aware that a configmap is updated on containers asynchronously and could take some time: a signal delivered before will be totally useless. I still didn't find a way to watch for a configmap update complete event, and a sleep looks even …

kubectl-rollout-configmap

#!/bin/bash

# Init
OPT_FROM_FILES=
OPT_DEPLOYMENT=
OPT_CONTAINER=
OPT_SIGNAL=
OPT_YES=0

# Helper to print usage
usage() {
    echo "Replaces a config map from file and (optionally) signal the main process in a container."
    echo ""
    echo "Usage: kubectl-rollout-configmap [options] <configmap>"
    echo ""
    echo "Options:"
    echo "  -f FILE          Configmap file or directory"
    echo "  -s SIGNAL        After replacing the configmap signal the pod container(s) in the specified deployment"
    echo "  -d DEPLOYMENT    The name of the deployment whose containers should be signaled"
    echo "  -c CONTAINER     The name of the container should be signaled (required if your pod has multiple containers)"
    echo "  -y               Always yes: do not ask before signaling (please note that it takes some time before a"
    echo "                   configmap is updated on containers, and the signal could be sent before it, making it"
    echo "                   useless)"
    echo ""
    echo "Examples:"
    echo "  Replace config map from a file and signal deployment containers"
    echo "  kubectl-rollout-configmap -f config.yaml -d nginx -s HUP nginx-config"
    echo ""

    exit 1
}

# Parse options
while getopts "f:d:c:s:yh" OPTION; do
    case "$OPTION" in
        f)
            OPT_FROM_FILES="${OPT_FROM_FILES} --from-file=${OPTARG}"
            ;;
        d)
            OPT_DEPLOYMENT=$OPTARG
            ;;
        c)
            OPT_CONTAINER=$OPTARG
            ;;
        s)
            OPT_SIGNAL=$OPTARG
            ;;
        y)
            OPT_YES=1
            ;;
        h)
            usage
            ;;
        *)
            # NOTE: getopts will print an error message
            exit 1
            ;;
    esac
done

# Get configmap name
shift $(($OPTIND - 1))
OPT_CONFIGMAP=$@

if [ -z "$OPT_CONFIGMAP" ]; then
    echo "The configmap name is missing. Please run kubectl-rollout-configmap -h for help."
    exit 1
fi

# Check if the configmap already exists
kubectl get configmap $OPT_CONFIGMAP > /dev/null 2> /dev/null
CONFIGMAP_EXISTS=$?

# Currently kubernetes doesn't allow to update a configmap
# from file, so we do create a new temporary configmap, replace
# the original one, delete the temporary one
if [ "$CONFIGMAP_EXISTS" -eq 0 ]; then
    UNIQ=$(date | md5 | fold -w 6 | head -n 1)
    CONFIGMAP_TMP="${OPT_CONFIGMAP}.${UNIQ}tmp"

    (kubectl create configmap $CONFIGMAP_TMP $OPT_FROM_FILES) && \
    (kubectl get configmap $CONFIGMAP_TMP -o yaml | sed "s/${CONFIGMAP_TMP}/${OPT_CONFIGMAP}/g" | sed -E "s/creationTimestamp:.*|resourceVersion:.*|selfLink:.*|uid:.*//g" | kubectl replace configmap $OPT_CONFIGMAP -f -) && \
    (kubectl delete configmap $CONFIGMAP_TMP)
else
    kubectl create configmap $OPT_CONFIGMAP $OPT_FROM_FILES
fi

if [ $? -ne 0 ]; then
    exit 1
fi

# Signaling
if [ -n "$OPT_SIGNAL" ]; then
    if [ $OPT_YES -eq 0 ]; then
        # Ask confirmation
        read -p "You are about to send signal $OPT_SIGNAL to $OPT_DEPLOYMENT. Continue? [yes/no] " -r
        echo ""

        if [ "$REPLY" == "yes" ]; then
            CONFIRMED=1
        fi
    else
        CONFIRMED=1
    fi

    if [ -n "$CONFIRMED" ]; then
        if [ -n "$OPT_DEPLOYMENT" ] && [ -z "$OPT_CONTAINER" ]; then
            # Signal without container selection
            kubectl get pods -l app="${OPT_DEPLOYMENT}" -o custom-columns=NAME:.metadata.name --no-headers | \
                xargs -I {} kubectl exec "{}" -- kill -${OPT_SIGNAL} 1
            echo "Signal sent"
        elif [ -n "$OPT_DEPLOYMENT" ] && [ -n "$OPT_CONTAINER" ]; then
            # Signal with container selection
            kubectl get pods -l app="${OPT_DEPLOYMENT}" -o custom-columns=NAME:.metadata.name --no-headers | \
                xargs -I {} kubectl exec "{}" -c "${OPT_CONTAINER}" -- kill -${OPT_SIGNAL} 1
            echo "Signal sent"
        else
            # Missing required option
            echo "Unable to signal because of missing deployment option: please add -d DEPLOYMENT"
            exit 1
        fi
    fi
fi