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dkr2sh - convert Dockerfile to shell script

This script naively translates some Dockerfile instructions into corresponding shell commands.

Conversion Rules

Instructions commented out

  • FROM
  • CMD
  • LABEL
  • MAINTAINER
  • EXPOSE
  • ENTRYPOINT
  • VOLUME
  • ARG
  • ONBUILD
  • STOPSIGNAL
  • HEALTHCHECK

Translate these instructions manually:

  • USER - execute the next block(s) with su or equivalent
  • SHELL - unwrap JSON-formatted arguments, run it for subsequent block(s)

ENV

Before:

ENV FOO bar

After:

export FOO=bar

RUN

Before:

RUN /usr/bin/foo \
    && /sbin/bar --quux

After:

/usr/bin/foo \
    && /sbin/bar --quux

COPY

COPY behaves differently on files and directories, so we use rsync to emulate recursive content copying on directories.

If --from argument is given, it becomes just a comment, because unlike Docker images (and ogres), shell scripts don't have layers.

Before:

COPY --from=composer foo.sh /usr/local/bin/

After:

for i in foo.sh; do
        test -d "$i" && i="$i/"
        rsync -a "$i" /usr/local/bin/ # --from=composer
done

WORKDIR

Before:

WORKDIR /var/lib/pgsql/10.1

After:

mkdir -p /var/lib/pgsql/10.1 && cd /var/lib/pgsql/10.1

ADD

ADD has many rules, and transforms into a fairly large snippet.

Before:

ADD https://example.org/foo.bin /opt

After:

if echo "/opt" | grep -q '/$'; then
        mkdir -p "/opt";
else
        mkdir -p "$(dirname "/opt")";
fi

for i in https://example.org/foo.bin; do
        if echo "$i" | grep -q '^\(https\?\|ftp\)://'; then
                if echo "/opt" | grep -q '/$'; then
                        (cd "/opt" && wget -q "$i");
                else
                        wget -q -O "/opt" "$i";
                fi
        elif test -d "$i"; then
                rsync -a "$i/" "/opt";
        elif tar -tf "$i" >/dev/null 2>&1; then
                mkdir -p "/opt" && tar -C "/opt" -xf "$i";
        else
                rsync -a "$i" "/opt";
        fi
done

Copyright

Copyright 2018, Development Gateway

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.