Alpine linux install specific (older) package version

At my project I use Docker-in-Docker images for GitLab CI.

And those are only Alpine-based.

And for some another dependency I needed a very specific version of openssh package installed. An older one. And I could not downgrade the whole version of Alpine I use.

And Alpine does not really allow you to install the older package versions in a way that e.g. Debian-based distros do when you can hook in another version repo and install from it (which is still not exactly recommended).

Long story short, what you CAN do is — build the needed package from source code and install it!

First — go to https://pkgs.alpinelinux.org/packages and find which Alpine version (branch) has the package version you need:

I need Alpine 3.7 e.g. but my main Alpine version is 3.11 which is much newer

Then in your main Alpine version do this:

# Install the build prerequisites.
apk add alpine-sdk sudo
# Create user and add it to the group.
# Because root can not build packages.
adduser -D packager && addgroup packager abuild
# Give him sudo access.
echo 'packager ALL=(ALL) NOPASSWD:ALL' >/etc/sudoers.d/packager
# Switch to that user
su packager
# Clone aports repo with the sources of all Alpine packages.
git clone git://git.alpinelinux.org/aports
# cd into your package dir
cd ~/aports/main/openssh
# Switch to the branch you found at the website.
git checkout 3.7-stable
# Create a signature certificate and build the package!
abuild-keygen -a -i -n && abuild -r
# Exit from the packager user back to root:
exit # or ctrl+d
# Find the package and install it:
cd /home/packager/packages/main/x86_64/ && apk add openssh-7.5_p1-r10.apk openssh-client-7.5_p1-r10.apk

And this can also be neatly wrapped into a single Docker layer command where we also do some cleanup at the end:

RUN apk add alpine-sdk sudo && \
    adduser -D packager && addgroup packager abuild && \
    echo 'packager ALL=(ALL) NOPASSWD:ALL' >/etc/sudoers.d/packager && \
    su - packager -c 'git clone git://git.alpinelinux.org/aports && \
    cd ~/aports/main/openssh && \
    git checkout 3.7-stable && \
    abuild-keygen -a -i -n && \
    abuild -r' && \
    cd /home/packager/packages/main/x86_64/ && \
    apk add openssh-7.5_p1-r10.apk openssh-client-7.5_p1-r10.apk && \
    apk del alpine-sdk sudo

Ciao and good luck!