Debian

Debian is a glibc and apt based distribution and the base under many language images such as python and node. The -slim variants drop docs and extras.

Documentation: Debian Reference Project: Debian · Docker Hub

See also Container Distros, Ubuntu and Dockerfile.

apt in Dockerfiles #

COMMAND	DESCRIPTION
`apt-get update`	Refresh indexes; always in the same `RUN` as the install
`apt-get install -y --no-install-recommends PACKAGE`	Install without recommended extras
`rm -rf /var/lib/apt/lists/*`	Remove the indexes at the end of the layer
`apt-get purge -y --auto-remove PACKAGE`	Remove a package and its unused dependencies
`apt-cache policy PACKAGE`	Installed and candidate versions
`dpkg -L PACKAGE`	List a package’s files
`dpkg -S /PATH/TO/FILE`	Which package owns a file
`cat /etc/debian_version`	Exact point release (`12.15` in the image checked)

dockerfile
FROM debian:12-slim
RUN apt-get update \
 && apt-get install -y --no-install-recommends ca-certificates curl \
 && rm -rf /var/lib/apt/lists/*

Image Tags #

TAG	MEANING
`debian:12`	Major release by number (preferred)
`debian:bookworm`	The same release by codename
`debian:12-slim` / `debian:bookworm-slim`	Smaller variant
`debian:stable` / `debian:stable-slim`	Follows the current stable release, so the major version changes over time
`debian:testing` / `debian:sid`	Moving development releases; not for production
`debian:bookworm-YYYYMMDD`	Dated tag for reproducibility (check the tag list on Docker Hub; unverified)

Users #

COMMAND	DESCRIPTION
`useradd -r -u 10001 APP`	Create a system user; a UID above 999 prints a `SYS_UID_MAX` warning but works
`useradd -u 10001 -m APP`	Create a regular user with a home directory
`groupadd -r GROUP`	Create a system group

CA Certificates and Timezone #

COMMAND	DESCRIPTION
`apt-get install -y --no-install-recommends ca-certificates`	Needed for HTTPS; not in the base image
`update-ca-certificates`	Rebuild after adding `.crt` files to `/usr/local/share/ca-certificates/`
`ln -fs /usr/share/zoneinfo/Europe/London /etc/localtime`	Set the timezone (`/usr/share/zoneinfo` is present in `debian:12`)
`-e TZ=Europe/London`	Alternative at `docker run` (unverified)

Gotchas #

SYMPTOM	FIX
`E: Unable to locate package`	Run `apt-get update` in the same `RUN`
`curl: (60) SSL certificate problem`	Install `ca-certificates`
Missing `ps`, `ping`	Install `procps`, `iputils-ping`
`stable` tag jumped to a new release	Pin the number or codename
Sources are in `/etc/apt/sources.list.d/debian.sources`	12 uses the deb822 format, not `sources.list`