Docker FROM debian:latest

So in my last article I created a Docker container with nothing but a statically compiled helloworld in it. That demonstrated how it’s possible to define a very very (very very) simple container.

Here I define a similarly simple container with more complex dependencies – a hello world perl script requiring the Modern::Perl perl module. Now I don’t even need to build the executable binary, but all of a sudden I need to include enough of an environment to support my simple perl script.

As far as working with Docker this is not much more complex than changing “FROM scratch” to “FROM debian:latest”. The result is a much bigger container which will take more resources to run, but other than providing the computing resources to support that I really don’t have to care about it that much.

The Dockerfile now looks like this:

FROM debian:latest

# Get base module requirements
RUN apt-get --assume-yes update &&\
    apt-get --assume-yes install libmodern-perl-perl

# Copy the script in place and start running
COPY hello.pl /
CMD ["/hello.pl"]

But the container build process is no longer a couple of lines:

$ make docker
docker build --rm -t bradhelloperl .
Sending build context to Docker daemon 4.096 kB
Sending build context to Docker daemon 
Step 0 : FROM debian:latest
latest: Pulling from debian
902b87aaaec9: Already exists 
9a61b6b1315e: Already exists 
Digest: sha256:b42e664a14b4ed96f7891103a6d0002a6ae2f09f5380c3171566bc5b6446a8ce
Status: Downloaded newer image for debian:latest
 ---> 9a61b6b1315e
Step 1 : RUN apt-get --assume-yes update &&    apt-get --assume-yes install libmodern-perl-perl
 ---> Running in afe73c43d3a8
Get:1 http://security.debian.org jessie/updates InRelease [63.1 kB]
Get:2 http://security.debian.org jessie/updates/main amd64 Packages [165 kB]
Get:3 http://httpredir.debian.org jessie InRelease [134 kB]
Get:4 http://httpredir.debian.org jessie-updates InRelease [123 kB]
Get:5 http://httpredir.debian.org jessie/main amd64 Packages [9038 kB]
Get:6 http://httpredir.debian.org jessie-updates/main amd64 Packages [3614 B]
Fetched 9527 kB in 40s (237 kB/s)
Reading package lists...
Reading package lists...
Building dependency tree...
Reading state information...
The following extra packages will be installed:
  libalgorithm-c3-perl libarchive-extract-perl libcgi-fast-perl libcgi-pm-perl
  libclass-c3-perl libclass-c3-xs-perl libcpan-meta-perl libdata-optlist-perl
  libdata-section-perl libfcgi-perl libgdbm3 liblog-message-perl
  liblog-message-simple-perl libmodule-build-perl libmodule-pluggable-perl
  libmodule-signature-perl libmro-compat-perl libpackage-constants-perl
  libparams-util-perl libpod-latex-perl libpod-readme-perl
  libregexp-common-perl libsoftware-license-perl libsub-exporter-perl
  libsub-install-perl libterm-ui-perl libtext-soundex-perl
  libtext-template-perl perl perl-modules rename
Suggested packages:
  perl-doc libterm-readline-gnu-perl libterm-readline-perl-perl make
  libb-lint-perl libcpanplus-dist-build-perl libcpanplus-perl
  libfile-checktree-perl libobject-accessor-perl
Recommended packages:
  libarchive-tar-perl
The following NEW packages will be installed:
  libalgorithm-c3-perl libarchive-extract-perl libcgi-fast-perl libcgi-pm-perl
  libclass-c3-perl libclass-c3-xs-perl libcpan-meta-perl libdata-optlist-perl
  libdata-section-perl libfcgi-perl libgdbm3 liblog-message-perl
  liblog-message-simple-perl libmodern-perl-perl libmodule-build-perl
  libmodule-pluggable-perl libmodule-signature-perl libmro-compat-perl
  libpackage-constants-perl libparams-util-perl libpod-latex-perl
  libpod-readme-perl libregexp-common-perl libsoftware-license-perl
  libsub-exporter-perl libsub-install-perl libterm-ui-perl
  libtext-soundex-perl libtext-template-perl perl perl-modules rename
0 upgraded, 32 newly installed, 0 to remove and 1 not upgraded.
Need to get 6606 kB of archives.
After this operation, 37.3 MB of additional disk space will be used.
Get:1 http://httpredir.debian.org/debian/ jessie/main libgdbm3 amd64 1.8.3-13.1 [30.0 kB]
Get:2 http://httpredir.debian.org/debian/ jessie/main libalgorithm-c3-perl all 0.09-1 [11.9 kB]
Get:3 http://httpredir.debian.org/debian/ jessie/main libarchive-extract-perl all 0.72-1 [24.8 kB]
Get:4 http://httpredir.debian.org/debian/ jessie/main perl-modules all 5.20.2-3+deb8u1 [2551 kB]
Get:5 http://httpredir.debian.org/debian/ jessie/main perl amd64 5.20.2-3+deb8u1 [2629 kB]
Get:6 http://httpredir.debian.org/debian/ jessie/main libcgi-pm-perl all 4.09-1 [213 kB]
Get:7 http://httpredir.debian.org/debian/ jessie/main libparams-util-perl amd64 1.07-2+b1 [23.5 kB]
Get:8 http://httpredir.debian.org/debian/ jessie/main libclass-c3-perl all 0.26-1 [22.9 kB]
Get:9 http://httpredir.debian.org/debian/ jessie/main libsub-exporter-perl all 0.986-1 [49.9 kB]
Get:10 http://httpredir.debian.org/debian/ jessie/main libdata-optlist-perl all 0.109-1 [10.6 kB]
Get:11 http://httpredir.debian.org/debian/ jessie/main libclass-c3-xs-perl amd64 0.13-2+b1 [15.2 kB]
Get:12 http://httpredir.debian.org/debian/ jessie/main libmodern-perl-perl all 1.20140107-1 [9964 B]
Get:13 http://httpredir.debian.org/debian/ jessie/main libmodule-build-perl all 0.421000-2 [265 kB]
Get:14 http://httpredir.debian.org/debian/ jessie/main libmodule-signature-perl all 0.73-1+deb8u2 [30.4 kB]
Get:15 http://httpredir.debian.org/debian/ jessie/main libmodule-pluggable-perl all 5.1-1 [25.0 kB]
Get:16 http://httpredir.debian.org/debian/ jessie/main libpackage-constants-perl all 0.04-1 [5820 B]
Get:17 http://httpredir.debian.org/debian/ jessie/main libpod-latex-perl all 0.61-1 [34.7 kB]
Get:18 http://httpredir.debian.org/debian/ jessie/main libregexp-common-perl all 2013031301-1 [173 kB]
Get:19 http://httpredir.debian.org/debian/ jessie/main libpod-readme-perl all 0.11-1 [15.3 kB]
Get:20 http://httpredir.debian.org/debian/ jessie/main libfcgi-perl amd64 0.77-1+b1 [39.1 kB]
Get:21 http://httpredir.debian.org/debian/ jessie/main libsoftware-license-perl all 0.103010-3 [119 kB]
Get:22 http://httpredir.debian.org/debian/ jessie/main libcgi-fast-perl all 1:2.04-1 [10.9 kB]
Get:23 http://httpredir.debian.org/debian/ jessie/main libcpan-meta-perl all 2.142690-1 [125 kB]
Get:24 http://httpredir.debian.org/debian/ jessie/main rename all 0.20-3 [12.4 kB]
Get:25 http://httpredir.debian.org/debian/ jessie/main libsub-install-perl all 0.928-1 [11.4 kB]
Get:26 http://httpredir.debian.org/debian/ jessie/main libmro-compat-perl all 0.12-1 [13.2 kB]
Get:27 http://httpredir.debian.org/debian/ jessie/main libdata-section-perl all 0.200006-1 [13.4 kB]
Get:28 http://httpredir.debian.org/debian/ jessie/main liblog-message-perl all 0.8-1 [26.0 kB]
Get:29 http://httpredir.debian.org/debian/ jessie/main liblog-message-simple-perl all 0.10-2 [8126 B]
Get:30 http://httpredir.debian.org/debian/ jessie/main libtext-template-perl all 1.46-1 [53.1 kB]
Get:31 http://httpredir.debian.org/debian/ jessie/main libterm-ui-perl all 0.42-1 [19.1 kB]
Get:32 http://httpredir.debian.org/debian/ jessie/main libtext-soundex-perl amd64 3.4-1+b2 [13.7 kB]
debconf: delaying package configuration, since apt-utils is not installed
Fetched 6606 kB in 16s (395 kB/s)
Selecting previously unselected package libgdbm3:amd64.
(Reading database ... 7528 files and directories currently installed.)
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Unpacking libgdbm3:amd64 (1.8.3-13.1) ...
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Unpacking perl-modules (5.20.2-3+deb8u1) ...
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Unpacking perl (5.20.2-3+deb8u1) ...
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Adding 'diversion of /usr/bin/config_data to /usr/bin/config_data.diverted by libmodule-build-perl'
Adding 'diversion of /usr/share/man/man1/config_data.1.gz to /usr/share/man/man1/config_data.diverted.1.gz by libmodule-build-perl'
Unpacking libmodule-build-perl (0.421000-2) ...
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Adding 'diversion of /usr/bin/pod2latex to /usr/bin/pod2latex.bundled by libpod-latex-perl'
Adding 'diversion of /usr/share/man/man1/pod2latex.1.gz to /usr/share/man/man1/pod2latex.bundled.1.gz by libpod-latex-perl'
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Unpacking rename (0.20-3) ...
Setting up libgdbm3:amd64 (1.8.3-13.1) ...
Setting up perl-modules (5.20.2-3+deb8u1) ...
Setting up perl (5.20.2-3+deb8u1) ...
update-alternatives: using /usr/bin/prename to provide /usr/bin/rename (rename) in auto mode
Setting up libalgorithm-c3-perl (0.09-1) ...
Setting up libarchive-extract-perl (0.72-1) ...
Setting up libcgi-pm-perl (4.09-1) ...
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Setting up libclass-c3-perl (0.26-1) ...
Setting up libclass-c3-xs-perl (0.13-2+b1) ...
Setting up libcpan-meta-perl (2.142690-1) ...
Setting up libparams-util-perl (1.07-2+b1) ...
Setting up libsub-install-perl (0.928-1) ...
Setting up libdata-optlist-perl (0.109-1) ...
Setting up libmro-compat-perl (0.12-1) ...
Setting up libsub-exporter-perl (0.986-1) ...
Setting up libdata-section-perl (0.200006-1) ...
Setting up liblog-message-perl (0.8-1) ...
Setting up liblog-message-simple-perl (0.10-2) ...
Setting up libmodern-perl-perl (1.20140107-1) ...
Setting up libmodule-build-perl (0.421000-2) ...
Setting up libmodule-pluggable-perl (5.1-1) ...
Setting up libmodule-signature-perl (0.73-1+deb8u2) ...
Setting up libpackage-constants-perl (0.04-1) ...
Setting up libpod-latex-perl (0.61-1) ...
Setting up libregexp-common-perl (2013031301-1) ...
Setting up libpod-readme-perl (0.11-1) ...
Setting up libtext-template-perl (1.46-1) ...
Setting up libsoftware-license-perl (0.103010-3) ...
Setting up libterm-ui-perl (0.42-1) ...
Setting up libtext-soundex-perl (3.4-1+b2) ...
Setting up rename (0.20-3) ...
update-alternatives: using /usr/bin/file-rename to provide /usr/bin/rename (rename) in auto mode
Processing triggers for libc-bin (2.19-18) ...
 ---> 5df0148ab594
Removing intermediate container afe73c43d3a8
Step 2 : COPY hello.pl /
 ---> 73621b2beb17
Removing intermediate container 073772d52012
Step 3 : CMD /hello.pl
 ---> Running in 32701bc83e03
 ---> 2ba9eec0fbfa
Removing intermediate container 32701bc83e03
Successfully built 2ba9eec0fbfa

And in this case I’ve create a perl script which loops forever to show what happens when a container keeps running:

#!/usr/bin/env perl

use Modern::Perl;

# autoflush output
$| = 1;

my $loop = 0;
while (1) {
    say "[${loop}] Hello World!";
    $loop++;
    sleep 1;
}

Now I start the container and ask it to run in the background:

$ make run
docker run -d bradhelloperl
e4cb410b97f18b70f18ba1a4b4ded3e310bc63f85dbaf58b776463ec4a61ab64

And to see what is being printed I view the container log:

 $ docker logs e4cb410b97f18b70f18ba1a4b4ded3e310bc63f85dbaf58b776463ec4a61ab64
[0] Hello World!
[1] Hello World!
[2] Hello World!
[3] Hello World!
[4] Hello World!
[5] Hello World!
[6] Hello World!
[7] Hello World!

And finally, I’ll have to kill this container off now as it’s going to run forever. To show a different way this can be done I’ll look up the human readable ID and use it instead:

$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
e4cb410b97f1        bradhelloperl       "/hello.pl"         4 minutes ago       Up 4 minutes                            silly_sinoussi 

$ docker kill silly_sinoussi
silly_sinoussi

$ docker rm silly_sinoussi
silly_sinoussi

Note I needed to both kill and remove the container. While the container was killed but not removed I could still view the logs (and see the final stdout output before the kill was run).

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