Fix docker user permissions issues

.docs/Docker.md

@@ -61,6 +61,17 @@ For more information, please refer to the [Dockerfile](https://github.com/Tyrrrz
 
 To get your Token and Channel IDs, please refer to [this page](Token-and-IDs.md).
 
+## Permissions issues
+
+This image was designed with a user running as uid:gid of 1000:1000.
+
+If your current user has different IDs, and you want to generate files directly editable for your user, you might want to run the container like this:
+
+```console
+mkdir data # or chown -R $(id -u):$(id -g) data
+docker run -it --rm -v $PWD/data:/out --user $(id -u):$(id -g) tyrrrz/discordchatexporter:stable export -t TOKEN -g CHANNELID
+```
+
 ## Environment variables
 
 DiscordChatExpoter CLI accepts the `DISCORD_TOKEN` environment variable as a fallback for the `--token` option. You can set this variable either with the `--env` Docker option or with a combination of the `--env-file` Docker option and a `.env` file.

DiscordChatExporter.Cli.dockerfile

@@ -40,20 +40,19 @@ LABEL org.opencontainers.image.licenses="MIT"
 
 # Alpine image doesn't come with the ICU libraries pre-installed, so we need to install them manually.
 # We need the full ICU data because we allow the user to specify any locale for formatting purposes.
-RUN apk add --no-cache icu-libs
-RUN apk add --no-cache icu-data-full
+RUN apk add --no-cache icu-libs icu-data-full
 ENV DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=false
 ENV LC_ALL=en_US.UTF-8
 ENV LANG=en_US.UTF-8
 
-# Use a non-root user to ensure that the files shared with the host are accessible by the host user
-# https://github.com/Tyrrrz/DiscordChatExporter/issues/851
-RUN adduser --disabled-password --no-create-home dce
-USER dce
+# Use a non-root user
+RUN apk add --no-cache su-exec
+RUN addgroup -S -g 1000 dce && adduser -S -H -G dce -u 1000 dce
 
 # This directory is exposed to the user for mounting purposes, so it's important that it always
 # stays the same for backwards compatibility.
 WORKDIR /out
 
 COPY --from=build /tmp/app/DiscordChatExporter.Cli/bin/publish /opt/app
-ENTRYPOINT ["/opt/app/DiscordChatExporter.Cli"]
+COPY docker-entrypoint.sh /
+ENTRYPOINT ["/docker-entrypoint.sh"]

docker-entrypoint.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env sh
+
+# If we are root, ensure the files in /out are writable
+# by the dce user and restart the process as the dce user
+if [ "$(id -u)" = '0' ]; then
+  chown -R dce:dce /out
+  exec su-exec dce "$0" "$@"
+fi
+
+exec /opt/app/DiscordChatExporter.Cli "$@"