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Creating Base Docker Image

Tested Infrastructure

Platform Number of Instance Reading Time
Play with Docker 1 5 min

Pre-requisite

  • Create an account with DockerHub
  • Open PWD Platform on your browser
  • Click on Add New Instance on the left side of the screen to bring up Alpine OS instance on the right side

Create base Docker image using debootstrap utility.

Install debootstrap package to create minimal Debian base system.

$ sudo apt-get install debootstrap

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  debootstrap
0 upgraded, 1 newly installed, 0 to remove and 1 not upgraded.
Need to get 66.5 kB of archives.
After this operation, 264 kB of additional disk space will be used.
Get:1 http://ftp.task.gda.pl/debian stretch/main amd64 debootstrap all 1.0.89 [66.5 kB]
Fetched 66.5 kB in 0s (216 kB/s) 
Selecting previously unselected package debootstrap.
(Reading database ... 47906 files and directories currently installed.)
Preparing to unpack .../debootstrap_1.0.89_all.deb ...
Unpacking debootstrap (1.0.89) ...
Processing triggers for man-db (2.7.6.1-2) ...
Setting up debootstrap (1.0.89) ...

Install dirmngr to enable network operations for managing and downloading certificates.

$ sudo apt-get install dirmngr

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Suggested packages:
  dbus-user-session pinentry-gnome3 tor
The following NEW packages will be installed:
  dirmngr
0 upgraded, 1 newly installed, 0 to remove and 1 not upgraded.
Need to get 595 kB of archives.
After this operation, 1,110 kB of additional disk space will be used.
Get:1 http://ftp.task.gda.pl/debian stretch/main amd64 dirmngr amd64 2.1.18-8~deb9u1 [595 kB]
Fetched 595 kB in 0s (1,599 kB/s)
Selecting previously unselected package dirmngr.
(Reading database ... 47969 files and directories currently installed.)
Preparing to unpack .../dirmngr_2.1.18-8~deb9u1_amd64.deb ...
Unpacking dirmngr (2.1.18-8~deb9u1) ...
Processing triggers for man-db (2.7.6.1-2) ...
Setting up dirmngr (2.1.18-8~deb9u1) ...

Download and store Debian signing key in case you use different Debian-based Linux distribution.

$ sudo apt-key --keyring /etc/apt/trusted.gpg.d/debian-archive-stretch-stable.gpg adv --keyserver pgpkeys.mit.edu --recv-keys EF0F382A1A7B6500

Executing: /tmp/apt-key-gpghome.8RuwguajVm/gpg.1.sh --keyserver pgpkeys.mit.edu --recv-keys EF0F382A1A7B6500
gpg: key EF0F382A1A7B6500: public key "Debian Stable Release Key (9/stretch) <[email protected]>" imported
gpg: Total number processed: 1
gpg:               imported: 1

Create base Debian system with enabled main, contrib and non-free components. Install dirmngr and apt-transport-https packages during this process.

$ sudo debootstrap --keyring /etc/apt/trusted.gpg.d/debian-archive-stretch-stable.gpg --force-check-gpg --variant=minbase --components=main,contrib,non-free --include=dirmngr,apt-transport-https --arch=amd64 stretch debian-stretch http://deb.debian.org/debian/

I: Retrieving InRelease 
I: Retrieving Release 
I: Retrieving Release.gpg 
I: Checking Release signature
I: Valid Release signature (key id 067E3C456BAE240ACEE88F6FEF0F382A1A7B6500)
I: Retrieving Packages 
I: Validating Packages 
I: Retrieving Packages 
I: Validating Packages 
I: Retrieving Packages 
I: Validating Packages 
I: Resolving dependencies of required packages...
I: Resolving dependencies of base packages...
I: Found additional required dependencies: libaudit-common libaudit1 libbz2-1.0 libcap-ng0 libdb5.3 libdebconfclient0 libgcrypt20 libgpg-error0 liblz4-1 libncursesw5 libsemanage-common libsemanage1 libsystemd0 libudev1 libustr-1.0-1 
I: Found additional base dependencies: adduser debian-archive-keyring gpgv libapt-pkg5.0 libassuan0 libcurl3-gnutls libffi6 libgmp10 libgnutls30 libgssapi-krb5-2 libhogweed4 libidn11 libidn2-0 libk5crypto3 libkeyutils1 libkrb5-3 libkrb5support0 libksba8 libldap-2.4-2 libldap-common libnettle6 libnghttp2-14 libnpth0 libp11-kit0 libpsl5 librtmp1 libsasl2-2 libsasl2-modules-db libssh2-1 libstdc++6 libtasn1-6 libunistring0 
I: Checking component main on http://deb.debian.org/debian...
I: Retrieving libacl1 2.2.52-3+b1
I: Validating libacl1 2.2.52-3+b1
I: Retrieving adduser 3.115
I: Validating adduser 3.115
I: Retrieving apt 1.4.8
I: Validating apt 1.4.8
I: Retrieving apt-transport-https 1.4.8
I: Validating apt-transport-https 1.4.8
[...]
I: Chosen extractor for .deb packages: dpkg-deb
I: Extracting libacl1...
I: Extracting libattr1...
I: Extracting libaudit-common...
I: Extracting libaudit1...
[...]
I: Installing core packages...
I: Unpacking required packages...
I: Unpacking libacl1:amd64...
I: Unpacking libattr1:amd64...
I: Unpacking libaudit-common...
I: Unpacking libaudit1:amd64...
[...]
I: Configuring required packages...
I: Configuring gcc-6-base:amd64...
I: Configuring lsb-base...
I: Configuring sensible-utils...
I: Configuring ncurses-base...
[...]
I: Unpacking the base system...
I: Unpacking adduser...
I: Unpacking apt...
I: Unpacking apt-transport-https...
I: Unpacking libapt-pkg5.0:amd64...
[...]
I: Configuring the base system...
I: Configuring libnpth0:amd64...
I: Configuring libnettle6:amd64...
I: Configuring libnghttp2-14:amd64...
I: Configuring libldap-common...
[...]
I: Base system installed successfully.

Initial base system size.

$ sudo du --human-readable --summarize debian-stretch

189M	debian-stretch

Mount udev, devpts, proc and sysfs filesystems inside created base system. You can skip this step for basic operations like these performed here.

$ sudo mount --bind /dev     debian-stretch/dev
$ sudo mount --bind /dev/pts debian-stretch/dev/pts
$ sudo mount --bind /proc    debian-stretch/proc
$ sudo mount --bind /sys     debian-stretch/sys

Change root directory.

$ sudo chroot debian-stretch

Assume yes answer for apt operations.

root@debian:/# echo "APT::Get::Assume-Yes \"true\";" | tee /etc/apt/apt.conf.d/10-assume_yes

APT::Get::Assume-Yes "true";

Install git utility inside the base system.

root@debian:/# apt-get install --no-install-recommends git

Remove non-essiential packages from the created base system.

root@debian:/# apt-get remove --allow-remove-essential e2fsprogs e2fslibs nano pinentry-curses whiptail kmod iptables iproute2 dmidecode

Remove downloaded packages from local repository.

root@debian:/# apt-get clean

Remove downloaded package lists.

root@debian:/# find /var/lib/apt/lists/ -maxdepth 2 -type f -delete

Exit chroot environment.

root@debian:/# exit

Detach filesystems mounted earlier inside created base system.

$ sudo umount debian-stretch/dev/pts
$ sudo umount debian-stretch/dev
$ sudo umount debian-stretch/proc
$ sudo umount debian-stretch/sys

Base system size after performed operations.

$ sudo du --human-readable --summarize debian-stretch

188M debian-stretch

Create archive with Debian base system.

$ sudo tar --verbose --create --file debian-stretch.tar --directory debian-stretch .

Archive size.

$ sudo du --human-readable debian-stretch.tar

173M debian-stretch.tar

Use docker to import image.

$ cat debian-stretch.tar | docker import - debian-stretch

Create simplest possible dockerfile using nginx to test created base image.

$ mkdir nginx

$ cat << EOF | tee nginx/Dockerfile
FROM "debian-stretch"

RUN \\
  apt-get update && \\
  apt-get install nginx

WORKDIR /etc/nginx

CMD ["nginx", "-g", "daemon off;"]

EXPOSE 80
EOF

FROM "debian-stretch"

RUN \
  apt-get update && \
  apt-get install nginx

WORKDIR /etc/nginx

CMD ["nginx", "-g", "daemon off;"]

EXPOSE 80

Build an image from created dockerfile.

$ docker build -t nginx-test nginx

Sending build context to Docker daemon  2.048kB
Step 1/5 : FROM "debian-stretch"
 ---> aa30c1dd3f7b
Step 2/5 : RUN   apt-get update &&   apt-get install nginx
 ---> Running in 6633f8d4b8ad
Ign:1 http://cdn-fastly.deb.debian.org/debian stretch InRelease
Get:2 http://cdn-fastly.deb.debian.org/debian stretch Release [118 kB]
Get:3 http://cdn-fastly.deb.debian.org/debian stretch Release.gpg [2434 B]
Get:4 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 Packages [7123 kB]
Get:5 http://cdn-fastly.deb.debian.org/debian stretch/main Translation-en [5393 kB]
Get:6 http://cdn-fastly.deb.debian.org/debian stretch/contrib amd64 Packages [50.9 kB]
Get:7 http://cdn-fastly.deb.debian.org/debian stretch/contrib Translation-en [45.9 kB]
Get:8 http://cdn-fastly.deb.debian.org/debian stretch/non-free amd64 Packages [78.0 kB]
Get:9 http://cdn-fastly.deb.debian.org/debian stretch/non-free Translation-en [79.2 kB]
Fetched 12.9 MB in 4s (2767 kB/s)
Reading package lists...
Reading package lists...
Building dependency tree...
Reading state information...
The following additional packages will be installed:
  fontconfig-config fonts-dejavu-core geoip-database libbsd0 libfontconfig1
  libfreetype6 libgd3 libgeoip1 libicu57 libjbig0 libjpeg62-turbo
  libnginx-mod-http-auth-pam libnginx-mod-http-dav-ext libnginx-mod-http-echo
  libnginx-mod-http-geoip libnginx-mod-http-image-filter
  libnginx-mod-http-subs-filter libnginx-mod-http-upstream-fair
  libnginx-mod-http-xslt-filter libnginx-mod-mail libnginx-mod-stream
  libpng16-16 libssl1.1 libtiff5 libwebp6 libx11-6 libx11-data libxau6 libxcb1
  libxdmcp6 libxml2 libxpm4 libxslt1.1 nginx-common nginx-full sgml-base ucf
  xml-core
Suggested packages:
  libgd-tools geoip-bin fcgiwrap nginx-doc ssl-cert sgml-base-doc debhelper
The following NEW packages will be installed:
  fontconfig-config fonts-dejavu-core geoip-database libbsd0 libfontconfig1
  libfreetype6 libgd3 libgeoip1 libicu57 libjbig0 libjpeg62-turbo
  libnginx-mod-http-auth-pam libnginx-mod-http-dav-ext libnginx-mod-http-echo
  libnginx-mod-http-geoip libnginx-mod-http-image-filter
  libnginx-mod-http-subs-filter libnginx-mod-http-upstream-fair
  libnginx-mod-http-xslt-filter libnginx-mod-mail libnginx-mod-stream
  libpng16-16 libssl1.1 libtiff5 libwebp6 libx11-6 libx11-data libxau6 libxcb1
  libxdmcp6 libxml2 libxpm4 libxslt1.1 nginx nginx-common nginx-full sgml-base
  ucf xml-core
0 upgraded, 39 newly installed, 0 to remove and 0 not upgraded.
Need to get 18.6 MB of archives.
After this operation, 58.9 MB of additional disk space will be used.
Get:1 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 libxau6 amd64 1:1.0.8-1 [20.7 kB]
Get:2 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 sgml-base all 1.29 [14.8 kB]
Get:3 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 libssl1.1 amd64 1.1.0f-3+deb9u1 [1342 kB]
[...]
Fetched 18.6 MB in 4s (3877 kB/s)
Selecting previously unselected package libxau6:amd64.
(Reading database ... 9191 files and directories currently installed.)
Preparing to unpack .../00-libxau6_1%3a1.0.8-1_amd64.deb ...
Unpacking libxau6:amd64 (1:1.0.8-1) ...
Selecting previously unselected package sgml-base.
Preparing to unpack .../01-sgml-base_1.29_all.deb ...
Unpacking sgml-base (1.29) ...
Selecting previously unselected package libssl1.1:amd64.
Preparing to unpack .../02-libssl1.1_1.1.0f-3+deb9u1_amd64.deb ...
[...]
Removing intermediate container 6633f8d4b8ad
 ---> 70f98486d676
Step 3/5 : WORKDIR /etc/nginx
Removing intermediate container a6a39756a14f
 ---> be74e0f6e790
Step 4/5 : CMD ["nginx", "-g", "daemon off;"]
 ---> Running in 6cd6d572d594
Removing intermediate container 6cd6d572d594
 ---> 6d4869b43380
Step 5/5 : EXPOSE 80
 ---> Running in a60697b44e55
Removing intermediate container a60697b44e55
 ---> f565d7bbf5ba
Successfully built f565d7bbf5ba
Successfully tagged nginx-test:latest

Run nginx process inside container (in foreground) using port 8080.

$ docker run -p 8080:80 --name nginx-test nginx-test

Request and display initial welcome web-page to test it.

$ wget --quiet --output-document - http://$(hostname):8080

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

You can use different terminal to verify redirected port.

$ docker ps

CONTAINER ID        IMAGE               COMMAND                  CREATED              STATUS              PORTS                  NAMES
84f17e2b8467        nginx-test          "nginx -g 'daemon of…"   About a minute ago   Up About a minute   0.0.0.0:8080->80/tcp   nginx-test