docker: Set the home directory for the user

[pierreprinetti]

Before this change, the docker user had home in a directory it had no
permissions on. The inability of creating a cache directory in $HOME
prevented npm to work properly.

Additionally, the node_modules in the base working directory had its
owner set to root, preventing further changes.

With this change, the etherpad user has a home directory.
Additionally, npm i is now run by etherpad rather than the root
user; this way, it is possible to dynamically change the node_modules
content in day 2 operations.

Note that while switching to the useradd builtin, a conflict was
discovered with the GID 65534 that was previously used. This change is
changing the etherpad user's UID to 5001 to avoid said conflict. As a
consequence, a chmod -R 5001:5001 must be run prior to attaching
volumes created from previous Etherpad versions.

[muxator]

I guess something like a chown -R in /opt/etherpad-liteafter the COPY statement is needed, because docker build complains:

$ docker build --tag muxator/etherpad .
[...]
Step 8/13 : COPY ./ ./
 ---> f882b96b2ccb
Step 9/13 : RUN bin/installDeps.sh
 ---> Running in 31ae5510747f
Copy the settings template to settings.json...
cp: cannot create regular file 'settings.json': Permission denied

It seems that the COPY ./ ./ statement populates /opt/etherpad-lite with root-owned files, even if USER etherpad:etherpad was already executed.

$ docker run -ti --rm 769477de80fd bash
etherpad@2da8f587ec10:/opt/etherpad-lite$ ls -ld /opt/etherpad-lite/
drwxr-xr-x 1 root root 326 Dec  1 18:56 /opt/etherpad-lite/
etherpad@2da8f587ec10:/opt/etherpad-lite$ ls -l /opt/etherpad-lite/
total 104
-rw-rw-r-- 1 root root 26442 Dec  1 18:24 CHANGELOG.md
-rw-rw-r-- 1 root root  8217 Oct 23 22:08 CONTRIBUTING.md
-rw-rw-r-- 1 root root  1424 Dec  1 18:55 Dockerfile
[...]

[pierreprinetti]

Interesting: Podman somehow made it work.

However, it seems to work with Docker now: https://travis-ci.org/ether/etherpad-lite/jobs/619350446

[muxator]

Queued, thanks