Perl script to build a Docker image from Dockerfile that creates the image in a single layer, without any intermediate images. Needs JSON CPAN module (available as `libjson-perl` Debian/Ubuntu package). Usage: run the script in the directory that contains a Dockerfile. More details in a blog post: http://3ofcoins.net/2013/09/22/flat-docker-images/…
#!/usr/bin/env perl | |
use feature 'switch'; | |
use strict; | |
use warnings; | |
use Data::Dumper; | |
use File::Basename; | |
use File::Copy; | |
use File::Path qw/make_path/; | |
use File::Temp qw/tempdir/; | |
use JSON; | |
our ( $from, $author, %metadata, @commands, $tmpdir, $tmpcount, $prefix ); | |
$tmpdir = tempdir(CLEANUP => !$ENV{LEAVE_TMPDIR}); | |
$tmpcount = 0; | |
$prefix = ''; | |
print "*** Working directory: $tmpdir\n" if $ENV{LEAVE_TMPDIR}; | |
open DOCKERFILE, '<Dockerfile' or die; | |
while ( <DOCKERFILE> ) { | |
chomp; | |
# handle long lines | |
$_ = "$prefix$_"; | |
$prefix = ''; | |
if ( /\\$/ ) { | |
s/\\$//; | |
$prefix="$_\n"; | |
next; | |
} | |
s/^\s*//; | |
/^#/ and next; | |
/^$/ and next; | |
my ($cmd, $args) = split(/\s+/, $_, 2); | |
given ( uc $cmd ) { | |
# building the image | |
when ('FROM') { $from = $args } | |
when ('RUN') { push @commands, $args } | |
when ('ADD') { | |
$tmpcount++; | |
my ( $src, $dest ) = split ' ', $args, 2; | |
if ( $src =~ /^https?:/ ) { | |
my $basename = basename($src); | |
my $target = "$tmpdir/dl/$tmpcount/$basename"; | |
make_path "$tmpdir/dl/$tmpcount"; | |
system('wget', '-O', $target, $src) == 0 or die; | |
$src = $target; | |
} | |
my $local = "$tmpdir/$tmpcount"; | |
given ( $src ) { | |
when ( /\.(tar(\.(gz|bz2|xz))?|tgz)$/ ) { | |
mkdir $local; | |
system('tar', '-C', $local, '-xf', $_) == 0 or die; | |
push @commands, "mkdir -p '$dest'", "( cd /.data/$tmpcount ; cp -a . '$dest' )"; | |
} | |
when ( -f $_ ) { | |
$dest .= basename($_) if ( $dest =~ /\/$/ ); | |
system('cp', '-a', $_, $local) == 0 or die; | |
push @commands, "mkdir -p '".dirname($dest)."'", "cp -a /.data/$tmpcount '$dest'"; | |
} | |
when ( -d $_ ) { | |
# Handle trailing slash combinations properly: | |
# - `$src=/dir, $dest=/foo -> /foo` | |
# - `$src=/dir, $dest=/foo/ -> /foo/dir` | |
# - `$src=/dir/, $dest=/foo -> /foo` | |
# - `$src=/dir/, $dest=/foo/ -> /foo` | |
$dest .= basename($_) if ( $_ !~ /\/$/ && $dest =~ /\/$/ ); | |
system('cp', '-a', $_, $local) == 0 or die; | |
push @commands, "mkdir -p '$dest'", "( cd /.data/$tmpcount ; cp -a . '$dest' )"; | |
} | |
default { die } | |
} | |
} | |
# image metadata | |
when ('MAINTAINER') { $author = $args } | |
when ('CMD') { $metadata{Cmd} = eval { decode_json($args) } || ['sh', '-c', $args] } | |
when ('ENTRYPOINT') { $metadata{Entrypoint} = eval { decode_json($args) } || ['sh', '-c', $args] } | |
when ('WORKDIR') { $metadata{WorkingDir} = $args } | |
when ('USER') { $metadata{User} = $args } | |
when ('EXPOSE') { push @{ $metadata{PortSpecs} ||= [] }, split(' ',$args); } | |
when ('ENV') { | |
my ( $k, $v ) = split(/s+/, $args, 2); | |
push @commands, "export $k='$v'"; | |
push @{ $metadata{Env} ||= [] }, "$k=$v"; | |
} | |
when ('VOLUME') { | |
# This seems to be a NOP in `docker build`. | |
# push @{ $metadata{VolumesFrom} ||= [] }, $args | |
} | |
} | |
} | |
close DOCKERFILE; | |
open SETUP, ">$tmpdir/setup.sh" or die; | |
print SETUP join("\n", "#!/bin/sh", "set -e -x", @commands), "\ntouch /.data/FINI\n"; | |
close SETUP; | |
chmod 0755, "$tmpdir/setup.sh"; | |
our @run = ('docker', 'run', "-cidfile=$tmpdir/CID", '-v', "$tmpdir:/.data", $from, "/.data/setup.sh"); | |
print "*** ", join(' ', @run), "\n"; | |
system(@run) == 0 or die; | |
die "unfinished, not committing\n" unless -f "$tmpdir/FINI"; | |
sleep 15; # docker container is not always immediately up to a commit, let's give it time to cool off. | |
open CID, "<$tmpdir/CID" or die; | |
our $cid = <CID>; | |
close CID; | |
our @commit = ( 'docker', 'commit' ); | |
push @commit, "-author=$author" if defined $author; | |
push @commit, "-run=" . encode_json(\%metadata) if %metadata; | |
push @commit, $cid; | |
print "*** ", join(' ', @commit), "\n"; | |
exec(@commit); |
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thaJeztah
commented
Jun 6, 2014
@mpasternacki Found some issues in your script;
I've created a modified version here; https://gist.github.com/thaJeztah/f5064ac9b285ba82b15c couldn't find an option to send a pull request for gists (not sure that's even possible) :) |
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grossws
commented
Oct 25, 2014
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atmoz commentedSep 22, 2013
Good stuff! This should be featured in Docker, or otherwise solved in a way that makes it easy to use without wasting unnecessary disk space.