为什么可以在Docker镜像中手动运行Java程序，但不能作为入口点

Question

我创建了一个openjdk-11高山docker映像并将我的jar复制到其中。我的Dockerfile是这样的：

FROM pwittchen/alpine-java11
VOLUME /tmp
ARG JAR_FILE
COPY ${JAR_FILE} /opt/app.jar
ENTRYPOINT ["java", "-jar", "/opt/app.jar"]

如果我运行：

docker run -it image

然后

Error loading shared library libjli.so: No such file or directory (needed by /usr/local/share/jdk-11/bin/java)
Error relocating /usr/local/share/jdk-11/bin/java: JLI_Launch: symbol not found
Error relocating /usr/local/share/jdk-11/bin/java: JLI_PreprocessArg: symbol not found
Error relocating /usr/local/share/jdk-11/bin/java: JLI_ReportMessage: symbol not found
Error relocating /usr/local/share/jdk-11/bin/java: JLI_StringDup: symbol not found
Error relocating /usr/local/share/jdk-11/bin/java: JLI_MemFree: symbol not found
Error relocating /usr/local/share/jdk-11/bin/java: JLI_InitArgProcessing: symbol not found
Error relocating /usr/local/share/jdk-11/bin/java: JLI_AddArgsFromEnvVar: symbol not found
Error relocating /usr/local/share/jdk-11/bin/java: JLI_List_add: symbol not found
Error relocating /usr/local/share/jdk-11/bin/java: JLI_List_new: symbol not found

但如果：

docker run -it --entrypoint /bin/sh image

然后我可以直接在shell中执行：

$ java -jar /opt/app.jar

而且有效。

为什么作为ENTRYPOINT运行会使libjli.so库阴影并尝试重新定位JLI*？

Answer 1

问题出在musl中。当您直接从shell执行时，musl能够读取库路径，但当您使用CMD和/或ENTRYPOINT执行时，musl无法解析库路径。

我在阅读后找到了这个，旧问题已经在openjdk8-alpine中解决了。那么这是一个回归。

https://github.com/docker-library/openjdk/issues/77

要解决这个问题，首先创建一个文件ld-musl-x86_64。pat指定musl所需的库的位置。文件内容如下所示：

/lib
/usr/lib
/usr/local/lib
/usr/local/share/jdk-11/lib/jli

在构建阶段将文件复制到docker映像。我的新Dockerfile如下所示：

FROM pwittchen/alpine-java11
VOLUME /tmp
ARG JAR_FILE
#Copy the configuration file with the Library path!
COPY ld-musl-x86_64.path /etc/ld-musl-x86_64.pat
COPY ${JAR_FILE} /opt/app.jar
ENTRYPOINT ["java", "-jar", "/opt/app.jar"]

终于开始工作了。