Output

bf-debug

Echoes "$1: $2" to stdout in grey with prefix (see ) - but only if BF_DEBUG is set to "1".

Arguments

1. Text to output

2. [Optional] Script / executable name

Usage

bf-done

Echoes 'done.' to stdout in green with prefix (see ).

Arguments

1. [Optional] Script / executable name

Usage

bf-e

Echoes $3 to stdout in colour $2 with prefix: "[$1] %Y-%m-%d %H:%M:%S".

Arguments

1. Namespace (default value for other output helper executables is 'bf')

2. ANSI colour code (see e.g. )

3. Text to output

Usage

bf-echo

Echoes "$1: $2" to stdout in default colour with prefix (see ).

Arguments

1. Text to output

2. [Optional] Script / executable name

Usage

bf-error

Echoes "$1: $2" to stdout in red with prefix (see ), and returns 1. This will end execution of the calling script if you use, e.g. set -euo pipefail at the top of your scripts (recommended).

Arguments

1. Text to output

2. [Optional] Script / executable name

Usage

bf-notok

Like echoes "$1: $2" to stdout in red with prefix, but doesn't end execution of calling script.

Arguments

1. Text to output

2. [Optional] Script / executable name

Usage

bf-ok

Echoes "$1: $2" to stdout in green with prefix.

Arguments

1. Text to output

2. [Optional] Script / executable name

Usage

Helpers

bf-adduser

Create user with id $2, group with id $3, both with name $1, and no password.

Arguments

1. User and group name

2. [Optional] User ID (default: 1000)

3. [Optional] Group ID (default: UID)

Usage

bf-ch

Changes ownership and/or permissions of file / directory glob.

Arguments

Required (one or both):

• -o X use chown to set ownership to "X"

• -m Y use chmod to set permissions to "Y"

Optional:

• -t f|d apply only to files ("f") or directories ("d")

• -rif -t is not specified, applies action recursively to all files and directories

Usage

bf-clear

Clears contents of /tmp and apk cache.

Usage

bf-esh

Calls esh in a consistent manner.

Arguments

1. Path to input (template) file

2. Path to output (generated) file

Usage

bf-image

Display name and version of the current image, and a link to the GitHub repository.

Usage

bf-install

Run install /tmp/install and then perform cleanup (see ). Within the ecosystem this would normally be used in a Dockerfile

Usage

This is the basic structure of Dockerfiles based on the Alpine S6 image, copying overlay and then running the standard installation.

bf-rmrf

Runs rm -rf $1 safely: doing nothing if $1 is empty. This is handy if the path you are deleting is contained in a variable (it effectively stops rm -rf /!).

Arguments

1. Folder path / file glob to delete.

Usage

bf-rnd

Generates a string of random letters and numbers of length $1.

Arguments

1. [Optional] Number of characters to return

Usage

bf-test-url

Uses wget to test URL $1.

Arguments

1. URL to test

Usage

bf-tz

Sets the container's timezone to $1. (Installs tzdata package, changes timezone and then removes tzdata).

Arguments

1. Valid timezone (e.g. Europe/London)

Usage

Note the change in time on line 12.

Source files (GitHub) Container images (Docker Hub)

Acknowledgements

Docker Alpine is a tiny distribution of Linux designed specifically for use in containers.

esh is a lightweight templating engine using POSIX-compatible syntax.

Tags

x.x and x.x.x refer to the bfren image versions.

In addition, you can add -dev and -beta suffixes to access development / test builds (see Docker Hub for further details).

Environment Variables

Packages

If you need to build the image with a different timezone to the default ("Europe/London"), you can do so by setting the TZ ARG, or by installing the tzdata package. (Please note this is only possible if you are building the image yourself - otherwise you will need to use .)

As well as the standard repositories, the edge repos are tagged with @edgemain and @edgecomm. This means you can, for example, do apk add curl@edgemain or apk add php8@edgecomm to add the edge versions of packages.

Cron

This image contains only one service: cron, which is enabled by default. If you want to add scripts or executables to the cron you have two options.

Option 1: /etc/periodic/

The simplest way to add tasks to the cron in Alpine Linux is to place an executable file in one of the directories under /etc/periodic/ (remember to set the executable attribute in /etc/fix-attrs.d/):

It's pretty obvious how frequently they run! An example of this method can be found in the image.

Option 2: /etc/crontabs/root

If you want more control over your cron tasks you can create a normal crontab file:

However, if you do this, remember you will be overriding the default file when your /overlay/ is copied over the image files, so you need to include the if you don't want to break the cron further down the line.

Templating with esh

The image comes pre-installed with , a simple shell-based templating engine. It is extremely lightweight, and very easy to use.

All dynamic configuration files in the bfren ecosystem are built using esh, and the default location for those templates is /etc/bf/templates.