Reconstruct a `docker run` command from a running container.

docker-reconstruct.sh

#!/usr/bin/env bash
#
# docker-reconstruct.sh — Reconstruct a `docker run` command from a running container.
# Usage: ./docker-reconstruct.sh <container_name_or_id>
#

set -euo pipefail

if [[ $# -lt 1 ]]; then
    echo "Usage: $0 <container_name_or_id>"
    exit 1
fi

C="$1"

if ! docker inspect "$C" &>/dev/null; then
    echo "Error: Container '$C' not found."
    exit 1
fi

i() { docker inspect --format="$1" "$C"; }

IMAGE=$(i '{{.Config.Image}}')
NAME=$(i '{{.Name}}' | sed 's/^\///')
HOSTNAME=$(i '{{.Config.Hostname}}')
USER=$(i '{{.Config.User}}')
WORKING_DIR=$(i '{{.Config.WorkingDir}}')
RESTART=$(i '{{.HostConfig.RestartPolicy.Name}}')
MAX_RETRY=$(i '{{.HostConfig.RestartPolicy.MaximumRetryCount}}')
NETWORK=$(i '{{.HostConfig.NetworkMode}}')
PID_MODE=$(i '{{.HostConfig.PidMode}}')
PRIVILEGED=$(i '{{.HostConfig.Privileged}}')
READONLY=$(i '{{.HostConfig.ReadonlyRootfs}}')
RUNTIME=$(i '{{.HostConfig.Runtime}}')
INIT=$(i '{{.HostConfig.Init}}')
MEMORY=$(i '{{.HostConfig.Memory}}')
CPUS=$(i '{{.HostConfig.NanoCpus}}')
STDIN_OPEN=$(i '{{.Config.OpenStdin}}')
TTY=$(i '{{.Config.Tty}}')
AUTO_REMOVE=$(i '{{.HostConfig.AutoRemove}}')

ARGS=()
ARGS+=(docker run)
ARGS+=(--name "$NAME" -d)

DEFAULT_HOST=$(i '{{slice .Id 0 12}}')
[[ -n "$HOSTNAME" && "$HOSTNAME" != "$DEFAULT_HOST" ]] && ARGS+=(--hostname "$HOSTNAME")
[[ -n "$USER" ]] && ARGS+=(--user "$USER")
[[ -n "$WORKING_DIR" ]] && ARGS+=(--workdir "$WORKING_DIR")
[[ "$STDIN_OPEN" == "true" ]] && ARGS+=(-i)
[[ "$TTY" == "true" ]] && ARGS+=(-t)
[[ "$AUTO_REMOVE" == "true" ]] && ARGS+=(--rm)
[[ "$PRIVILEGED" == "true" ]] && ARGS+=(--privileged)
[[ "$READONLY" == "true" ]] && ARGS+=(--read-only)
[[ "$INIT" == "true" ]] && ARGS+=(--init)

if [[ -n "$RESTART" && "$RESTART" != "no" ]]; then
    if [[ "$RESTART" == "on-failure" && "$MAX_RETRY" -gt 0 ]]; then
        ARGS+=(--restart "${RESTART}:${MAX_RETRY}")
    else
        ARGS+=(--restart "$RESTART")
    fi
fi

[[ -n "$NETWORK" && "$NETWORK" != "default" ]] && ARGS+=(--network "$NETWORK")
[[ -n "$PID_MODE" ]] && ARGS+=(--pid "$PID_MODE")
[[ -n "$RUNTIME" && "$RUNTIME" != "runc" ]] && ARGS+=(--runtime "$RUNTIME")
[[ "$MEMORY" -gt 0 ]] && ARGS+=(--memory "$MEMORY")
[[ "$CPUS" -gt 0 ]] && ARGS+=(--cpus "$(awk "BEGIN {printf \"%.2f\", $CPUS / 1000000000}")")

# Port bindings
while IFS= read -r port; do
    [[ -z "$port" ]] && continue
    ARGS+=(-p "$(echo "$port" | sed 's/^://')")
done <<< "$(docker inspect --format='{{range $cp, $b := .HostConfig.PortBindings}}{{range $b}}{{.HostIp}}:{{.HostPort}}:{{$cp}}{{println}}{{end}}{{end}}' "$C")"

# Volume / bind mounts
while IFS= read -r mount; do
    [[ -z "$mount" ]] && continue
    TYPE=$(echo "$mount" | cut -d'|' -f1)
    SRC=$(echo "$mount" | cut -d'|' -f2)
    DST=$(echo "$mount" | cut -d'|' -f3)
    MODE=$(echo "$mount" | cut -d'|' -f4)
    if [[ "$TYPE" == "tmpfs" ]]; then
        ARGS+=(--tmpfs "$DST")
    else
        M="${SRC}:${DST}"
        [[ -n "$MODE" ]] && M+=":${MODE}"
        ARGS+=(-v "$M")
    fi
done <<< "$(docker inspect --format='{{range .Mounts}}{{.Type}}|{{.Source}}|{{.Destination}}|{{.Mode}}{{println}}{{end}}' "$C")"

# Cap add/drop
while IFS= read -r cap; do [[ -n "$cap" ]] && ARGS+=(--cap-add "$cap"); done <<< "$(i '{{range .HostConfig.CapAdd}}{{.}}{{println}}{{end}}')"
while IFS= read -r cap; do [[ -n "$cap" ]] && ARGS+=(--cap-drop "$cap"); done <<< "$(i '{{range .HostConfig.CapDrop}}{{.}}{{println}}{{end}}')"

# Devices
while IFS= read -r dev; do [[ -n "$dev" ]] && ARGS+=(--device "$dev"); done <<< "$(i '{{range .HostConfig.Devices}}{{.PathOnHost}}:{{.PathInContainer}}:{{.CgroupPermissions}}{{println}}{{end}}')"

# Image
ARGS+=("$IMAGE")

# Command args — only if no custom entrypoint (let the image handle it)
ENTRYPOINT=$(i '{{json .Config.Entrypoint}}')
if [[ "$ENTRYPOINT" == "null" || "$ENTRYPOINT" == "[]" ]]; then
    CMD_JSON=$(i '{{json .Config.Cmd}}')
    if [[ "$CMD_JSON" != "null" && "$CMD_JSON" != "[]" ]]; then
        while IFS= read -r arg; do
            ARGS+=("$arg")
        done <<< "$(echo "$CMD_JSON" | python3 -c "import sys,json
for a in json.load(sys.stdin): print(a)")"
    fi
fi

# Output as a properly shell-quoted string, ready for eval
printf '%q ' "${ARGS[@]}"
echo