docker-enter.sh

#!/bin/sh
COMMAND_ENV="env -i TERM=screen LANG=C LC_ALL=C"

if [ -e $(dirname "$0")/nsenter ]; then
    # with boot2docker, nsenter is not in the PATH but it is in the same folder
    NSENTER=$(dirname "$0")/nsenter
else
    NSENTER=nsenter
fi

if [ -z "$1" ]; then
    echo "Usage: `basename "$0"` CONTAINER [COMMAND [ARG]...]"
    echo ""
    echo "Enters the Docker CONTAINER and executes the specified COMMAND."
    echo "If COMMAND is not specified, runs an interactive shell in CONTAINER."
else
    # use docker exec if docker version >= 1.3.0
    if docker version | env -i LANG=C LC_ALL=C perl -Mversion -ne 'm/Server version: (\S+)/ && exit(version->parse(qq($1)) >= version->parse(qq(1.3.0)) ? 0 : 1)'; then
        CID=$(docker inspect --format "{{.Id}}" "$1")
        if [ -z "$CID" ]; then
            exit 1
        fi
        shift

        if [ -z "$1" ]; then
            exec docker -- exec -it $CID $COMMAND_ENV su -s /bin/bash
        else
            exec docker -- exec -it $CID $COMMAND_ENV "$@"
        fi
    fi

    # use nsenter if docker version < 1.3.0
    PID=$(docker inspect --format "{{.State.Pid}}" "$1")
    if [ -z "$PID" ]; then
        exit 1
    fi
    shift

    OPTS="--target $PID --mount --uts --ipc --net --pid --"

    if [ -z "$1" ]; then
        # No command given.
        # Use su to clear all host environment variables except for TERM,
        # initialize the environment variables HOME, SHELL, USER, LOGNAME, PATH,
        # and start a login shell.
        exec "$NSENTER" $OPTS $COMMAND_ENV su -s /bin/bash
    else
        # Use env to clear all host environment variables.
        exec "$NSENTER" $OPTS $COMMAND_ENV "$@"
    fi
fi