Hardcode them to:
SYNC_PORT=8080
SYNC_BASE=/anki_data
If these env variables are passed into the container with different values,
they are ignored.
The reasons is if the user modifies SYNC_BASE they risk data loss since
anki-sync-server will no longer write data into the volume. If they change
SYNC_PORT they need to also change it when mapping this internal port to the
external port of the container, which could be confusing plus it has no benefit
to allow this since it's always possible to change the external port even if
the internal port is fixed to 8080 (e.g. `-p 1234:8080`).
In both cases there is no benefit to making these values configurable and there
are risks associated.
Unfortunately there is no easy way of implementing this for the
Dockerfile.distroless so it's up to the user not to modify these values.
PUID and PGID are optional env variables to specify the user and group id of
the user that the anki-sync-server process should run with.
This gives more flexibility for solving permission problems with volumes and is
a common pattern for Docker images (e.g. see here:
https://docs.linuxserver.io/general/understanding-puid-and-pgid/)
The anki-sync-server process will write any files with the permissions of the
user it's running with, which can be a problem when you need to access those
files from outside the container or when they are being written into a bind
mount that is owned by a particular user on the host system.
To be able to implement this the entrypoint.sh needs to run as root (since it
needs to create a user and change file permissions). anki-sync-server then
needs to be started with the user 'anki', which is why the new dependency
'su-exec' is required. The user 'anki' and group 'anki-group' can no longer be
created at image build time because then their ids would be fixed.
Also update the build instructions to require building the Docker image inside
the directory where the Dockerfile resides since the build now needs to copy
the entrypoint.sh and it seems wrong the specify the path
docs/syncserver/entrypoint.sh inside the Dockerfile.
