SOLR-17353 Remove gosu binary from the Docker image (#4285)

Author: janhoy

changelog/unreleased/SOLR-17353-remove-gosu-from-docker.yml

@@ -0,0 +1,8 @@
+# See https://github.com/apache/solr/blob/main/dev-docs/changelog.adoc
+title: Remove gosu from the Docker image. The Solr Docker image no longer installs the gosu binary.
+type: removed
+authors:
+  - name: Jan Høydahl
+links:
+- name: SOLR-17353
+  url: https://issues.apache.org/jira/browse/SOLR-17353

solr/docker/templates/Dockerfile.body.template

@@ -69,7 +69,7 @@ RUN set -ex; \
 
 RUN set -ex; \
     apt-get update; \
-    apt-get -y --no-install-recommends install curl acl lsof procps wget netcat-openbsd gosu tini jattach; \
+    apt-get -y --no-install-recommends install curl acl lsof procps wget netcat-openbsd tini jattach; \
     rm -rf /var/lib/apt/lists/*;
 
 VOLUME /var/solr

solr/docker/tests/cases/gosu/test.sh

@@ -331,3 +331,7 @@ Older segments will continue to be readable.
 
 WARNING: After upgrading to Solr 10.1, downgrading to an earlier Solr 10.0.x version may fail because the older version does not include the `Lucene104` codec needed to read the newly written segments.
 If you require the ability to roll back, back up your indexes before upgrading.
+
+=== Docker
+
+The `gosu` binary is no longer installed in the Solr Docker image. See https://github.com/tianon/gosu[gosu github page] for alternatives, such as `runuser`, `setpriv` or `chroot`.