ioc: ensure single UID is used in containers.

IOC images do not require multiple users. Ensure all applications and
filesystem files satisfy this restriction, so that no issues occur at
runtime.

CHANGES.md

@@ -7,6 +7,13 @@
 * base: remove CALC dependency on Sequencer. by @henriquesimoes in
   https://github.com/cnpem/epics-in-docker/pull/68.
 
+### Bug fixes
+
+* ioc: ensure single UID is used in containers. by @henriquesimoes in
+  https://github.com/cnpem/epics-in-docker/69
+  * This allows to use ignore_chown_errors=True without subuid and subgid, but
+    still have everything working, especially apt.
+
 ### New features
 
 * base: add IOCStats module. by @gustavosr8 in

Dockerfile

@@ -10,6 +10,9 @@ ARG RUNTIME_PACKAGES
 ARG RUNTIME_TAR_PACKAGES
 ARG RUNTIME_PIP_PACKAGES
 
+COPY --from=build-image /usr/local/bin/lnls-single-uid /usr/local/bin/lnls-single-uid
+RUN lnls-single-uid
+
 RUN apt update -y && \
     apt install -y --no-install-recommends \
         libreadline8 \