Before getting into creating a Docker image from Debian's debootstrap, here is the link to the docker articles on the blog.

The first thing to do is install debootstrap:

#apt-get install debootstrap

Next, create a directory to build the debootstrap chroot:

mkdir debian-jaula

Now run debootstrap, passing the distribution to download, the directory where the chroot is created and the repository to use:

debootstrap jessie debian-jaula/ http://ftp.debian.org/debian
I: Retrieving Release 
I: Retrieving Release.gpg 
I: Checking Release signature
I: Valid Release signature (key id 75DDC3C4A499F1A18CB5F3C8CBF8D6FD518E17E1)
I: Validating Packages 
I: Resolving dependencies of required packages...
I: Resolving dependencies of base packages...
I: Found additional required dependencies: acl adduser dmsetup insserv libaudit-common libaudit1 libbz2-1.0 libcap2 libcap2-bin libcryptsetup4 libdb5.3 libdebconfclient0 libdevmapper1.02.1 libgcrypt20 libgpg-error0 libkmod2 libncursesw5 libprocps3 libsemanage-common libsemanage1 libslang2 libsystemd0 libudev1 libustr-1.0-1 procps systemd systemd-sysv udev 
I: Found additional base dependencies: libdns-export100 libffi6 libgmp10 libgnutls-deb0-28 libgnutls-openssl27 libhogweed2 libicu52 libidn11 libirs-export91 libisc-export95 libisccfg-export90 libmnl0 libnetfilter-acct1 libnettle4 libnfnetlink0 libp11-kit0 libpsl0 libtasn1-6 
I: Checking component main on http://ftp.debian.org/debian...
I: Validating acl 2.2.52-2
I: Retrieving libacl1 2.2.52-2
I: Validating libacl1 2.2.52-2
........................
..............
I: Configuring isc-dhcp-client...
I: Configuring tasksel...
I: Configuring tasksel-data...
I: Configuring libc-bin...
I: Configuring systemd...
I: Base system installed successfully.

Now the contents of the directory are shown:

ls debian-jaula/
bin/  boot/  dev/  etc/  home/  lib/  lib64/  media/  mnt/  opt/  proc/  root/  run/  sbin/  srv/  sys/  tmp/  usr/  var/

Now create the image using tar and docker import:

tar -C debian-jaula/ -c . | docker import - ecrespo/debian
sha256:49ad34e39c5f9ede2c1c57994895065236a5965496631e8fcab00b00778d85fa

As you can see, the image is generated along with its ID in sha256; the part that identifies the image is underlined, and the images are listed.

Running docker images gives the following:

REPOSITORY                                        TAG                 IMAGE ID            CREATED             SIZE
ecrespo/debian                                    latest              49ad34e39c5f        2 minutes ago       272.7 MB

With the chroot ready, you can make customizations and adaptations in order to create the docker image.

This article is based on the documentation in the Debian wiki about debootstrap and on an article about the docker base image.

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