TL;DR

Another post about Busybox, this time more pragmatic.

It happened to me to debug a few things inside a running image (yes, a sin but it was only temporary and saved a lot of time with re-building the whole thing at all rounds). Fact is that I couldn’t find how to install a new package inside herokuish when inside the container… and I needed an editor.

So presto! Busybox - multipurpose executable does include a tiny version of vi, so I downloaded it (luckily enough herokuish includes curl) and made a link to it named vi, living in $PATH. Yay!

Anticipating that I will need it also in the future… here’s a small snippet:

fetch-busybox.sh 226 B

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#!/bin/sh
url='https://busybox.net/downloads/binaries/1.31.0-defconfig-multiarch-musl/busybox-x86_64'
curl -Lo busybox "$url" &&
chmod +x busybox
printf './busybox --install . # installs all aliases in the current directory\n'

install-busybox.sh 405 B

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#!/bin/sh
url='https://busybox.net/downloads/binaries/1.31.0-defconfig-multiarch-musl/busybox-x86_64'
case "$1" in
    (--go)
        curl -Lo busybox "$url" &&
        chmod +x busybox &&
        ./busybox --install .
        ;;
    (*)
        cat >&2 <<END
WARNING: this installs busybox and ALL ITS ALIASES in the current directory.
If you are OK, re-run as: $0 --go
END
        exit 1
        ;;
esac

Local version here (pointing to a local version of the Busybox binary, good for X86_64).

I actually included a slightly different version of the above script in the source for the image, inside a standalone directory that is in $PATH inside the container:

#!/bin/sh
cd "$(dirname "$(readlink -f "$0")")"
curl -Lo busybox 'https://busybox.net/downloads/binaries/1.31.0-defconfig-multiarch-musl/busybox-x86_64'
chmod +x busybox
./busybox --install .

It removes the checks and makes sure to install Busybox in the same directory where the script lives… whichever is more useful is totally up to you!