i'm lately experimenting docker. try build image architecture looking easy maintenance , extensibility.
i built images following dockerfiles , curious different container sizes. why differ much?
following base/dockerfile results in 210.9 mb image (ubuntu:trusty having 188 mb that's okay).
from ubuntu:trusty run apt-get -qq update && \ debian_frontend=noninteractive apt-get -qq install \ nano env term xterm run apt-get -y autoremove && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* apache/dockerfile results in 224.4 mb.
from ubuntu:trusty run apt-get -qq update && \ debian_frontend=noninteractive apt-get -qq install \ nano \ apache2 env term xterm run apt-get -y autoremove && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* copy apache2-foreground /usr/local/bin/ run chmod a+x /usr/local/bin/apache2-foreground expose 80 workdir /var/www/html cmd ["apache2-foreground"] apache-php/dockerfile results in 266.7 mb.
from ubuntu:trusty run apt-get -qq update && \ debian_frontend=noninteractive apt-get -qq install \ nano curl \ apache2 \ libapache2-mod-php5 php5-mysql php5-mcrypt php5-gd php5-curl php-pear php-apc && \ curl -ss https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer run /usr/sbin/php5enmod mcrypt # + last 7 lines apache/dockerfile that's fine far haven't used inheritance until now. let's have look:
why apache-php-on-base/dockerfile result in 289.4 mb? it's same steps split in 2 images. have expected little overhead not 10 %.
from base # + apache-php/dockerfile without "install nano" it's bigger using multiple inheritance: apache-php-on-apache-on-base/dockerfile results in 314.9 mb.
from apache-on-base # + apache-php/dockerfile without "install nano apache2" where apache-on-base/dockerfile of course (resulting in 247 mb):
from base # + apache/dockerfile without "install nano" question: there way preventing images growing large while preserving maintainability?
update: implementing thajeztah's suggestions got following :) again!
repository tag image id created size apache-php-on-aob latest 2cf12a3b5872 2 minutes ago 249.9 mb apache-on-base latest 121c8a098ff5 3 minutes ago 203.7 mb base latest ee95e4f8aaee 3 minutes ago 189.3 mb apache-php-on-aob v1 e43df5e61aed 3 days ago 314.9 mb apache-on-base v1 c291f91f1a10 3 days ago 247 mb base v1 b181fc6f181d 3 days ago 210.9 mb ubuntu trusty 97434d46f197 10 days ago 188 mb
without going through differences in depth, reason you're not taking layered filesystem account.
docker creates new imagelayer each instruction in dockerfile. happens (very simplified):
so, become first layer:
from ubuntu:trusty (and docker like)
docker build -t layer1 . this become second layer:
from layer1 run apt-get -qq update && \ debian_frontend=noninteractive apt-get -qq install \ nano (and docker like)
docker build -t layer2 . and on.
the final image combination of images "stacked". important thing realize there file that's added in "layer1", removed in "layer2" still part of image; docker marks "removed" in layer2, doesn't make image smaller.
let's have @ first dockerfile. can see you're adding lot of files in first run instruction, add empty layer sets env var, followed run removes redundant files first run. however, files aren't removed earlier layer, still take space in final image;
from ubuntu:trusty run apt-get -qq update && \ debian_frontend=noninteractive apt-get -qq install \ nano env term xterm run apt-get -y autoremove && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* after building (docker build -t foobar .), gives me:
repository tag image id created size foobar latest 363aa5572838 2 minutes ago 210.9 mb making small change, , combine 2 run instructions, both apt-get update , apt-get clean steps take place in same run, same layer;
from ubuntu:trusty run apt-get -qq update && \ debian_frontend=noninteractive apt-get -qq install \ nano && \ apt-get -y autoremove && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* env term xterm and building that, produces image:
repository tag image id created size foobar latest ac8fb5e4db16 9 minutes ago 189.3 mb that's 20mb smaller!
you can read more in dockerfile best practice section of documentation.
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