Add a new alias to an existing container from a container running within a docker network

add_docker_alias.sh

#! /bin/sh

# Requires curl, jq & /var/run/docker.sock to be mounted into the container

set -eu

main() {
  alias=$1

  container_id="$(hostname)"

  original_network_config="$(original_network_config "$container_id")"

  updated_network_config="$(add_alias "$original_network_config" "$alias")"

  network_id="$(echo "$original_network_config" | jq -r '.NetworkID')"

  disconnect_container "$container_id" "$network_id"

  connect_container "$container_id" "$network_id" "$updated_network_config"
}

original_network_config() {
  container_id=$1

  curl \
    -sS \
    --unix-socket /var/run/docker.sock \
    "http://v1.41/containers/$container_id/json" \
    | jq '.NetworkSettings.Networks | to_entries[0] | .value'
}

add_alias() {
  original_network_config=$1
  alias=$2

  echo "$original_network_config" | jq '.Aliases += ["'"$alias"'"]'
}

disconnect_container() {
  container_id=$1
  network_id=$2

  curl \
    -sS \
    -H 'Content-Type: application/json' \
    -d '{"Container": "'"$container_id"'"}' \
    --unix-socket /var/run/docker.sock \
    "http://v1.41/networks/$network_id/disconnect"
}

connect_container() {
  container_id=$1
  network_id=$2
  updated_network_config=$3

  curl \
    -sS \
    -H 'Content-Type: application/json' \
    -d '{"Container": "'"$container_id"'", "EndpointConfig": '"$updated_network_config"'}' \
    --unix-socket /var/run/docker.sock \
    "http://v1.41/networks/$network_id/connect"
}

main "$@"