Add config-nsswitch which sets up basic name lookup

ENV PATH=/scripts:/bin

COPY --from=collect /stage /

COPY collect-binaries.bash /scripts/collect-binaries

COPY config-nsswitch.bash /scripts/config-nsswitch

ENTRYPOINT ["/bin/bash"]

#!/bin/bash

# Copyright (c) 2020 Dom Sekotill <dom.sekotill@kodo.org.uk>

#

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

# in the Software without restriction, including without limitation the rights

# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

# copies of the Software, and to permit persons to whom the Software is

# furnished to do so, subject to the following conditions:

#

# The above copyright notice and this permission notice shall be included in all

# copies or substantial portions of the Software.

#

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

# SOFTWARE.

set -eu -o pipefail

declare -r DEFAULT_STAGE=/stage

USAGE="Usage: $0 [--help] [-s STAGE] [USERNAME[:GROUP[,GROUP...]] ...]

Prepare the necessary libraries and configuration for name lookups with nsswitch

The Name Service Switch system is used by the GNU C library to provide various

types of name lookup including: user names, group names, and host names.  This

script configures an image for those name look-ups.

Hostname lookups are configured to use /etc/hosts (as supplied by Docker) and

DNS.  Users and groups are configured from command line arguments which supply

usernames and optional comma separated group names.  Only *additional* groups

need be specified, not the user's default group which has the same name as the

user.  The root user is always created if not specified.

Options:

  -h|--help         Show this message and exit.

  -s|--stage STAGE  Set the output stage directory. If it does not exist it will

                    be created. (default: $DEFAULT_STAGE)

Environment:

  STAGE:  An alternate way of providing --stage

"

add_group() {

	local IFS= users=${GROUP_USERS[$1]-}

	echo "$1:x:$2:${users%,}" >>$STAGE/etc/group

	unset GROUP_USERS[$1]

}

add_user() {

	echo "$1:x:$2:$2::/:/bin/nologin" >>$STAGE/etc/passwd

}

process_userspec()

{

	declare -a USERS=()

	declare -A GROUP_USERS=()

	declare -a groups

	local IFS=, spec user group i

	for spec in "$@"; do

		user=${spec%:*}

		groups=( ${spec#*:} )

		USERS+=( $user )

		GROUP_USERS[$user]+=""

		for group in "${groups[@]}"; do

			[[ $group = $user ]] && continue

			GROUP_USERS[$group]+="$user,"

		done

	done

	add_user root 0

	add_group root 0

	i=0

	for user in "${USERS[@]}"; do

		add_user $user $((++i))

		add_group $user $i

	done

	i=500

	for group in "${!GROUP_USERS[@]}"; do

		add_group $group $((i++))

	done

	cat <<-END_CONF >$STAGE/etc/nsswitch.conf

		passwd: files

		group:  files

		hosts:  files dns

	END_CONF

}

export PATH+=:$(dirname $0)

export STAGE=${STAGE-$DEFAULT_STAGE}

declare -a USERSPEC=()

until [[ $# -eq 0 ]]; do

	case $1 in

		-h|--help) echo "$USAGE"; exit 0 ;;

		-s|--stage) STAGE=$2; shift ;;

		--*=*) set -- ${1%=*} ${1#--*=} "${@:2}"; continue ;;

		--) USERSPEC+=( "$@" ); break ;;

		*) USERSPEC+=( "$1" ) ;;

	esac

	shift

done

mkdir -p $STAGE/etc

collect-binaries /lib/*/libnss*

process_userspec "${USERSPEC[@]}"