Dockerfile添加启动脚本后执行报错：文件存在却提示不存在

我编写了如下Dockerfile：

FROM alpine:latest
WORKDIR /app
RUN echo -e "#!/bin/bash\necho test" > /app/test.sh
RUN chmod 744 /app/test.sh
ENTRYPOINT [ "/app/test.sh" ]

运行容器时，却报错：exec /app/test.sh: no such file or directory。

我尝试在ENTRYPOINT前添加命令验证文件状态：

FROM alpine:latest
WORKDIR /app
RUN echo -e "#!/bin/bash\necho test" > /app/test.sh
RUN chmod 744 /app/test.sh
RUN ls -al && exit 1
ENTRYPOINT [ "/app/test.sh" ]

构建结果显示test.sh确实存在且拥有执行权限：

[+] Building 0.6s (8/8) FINISHED                                                                                        docker:default
 => [internal] load build definition from Dockerfile                                                                              0.0s
 => => transferring dockerfile: 200B                                                                                              0.0s
 => [internal] load metadata for docker.io/library/alpine:latest                                                                  0.3s
 => [internal] load .dockerignore                                                                                                 0.0s
 => => transferring context: 2B                                                                                                   0.0s
 => [1/5] FROM docker.io/library/alpine:latest@sha256:77726ef6b57ddf65bb551896826ec38bc3e53f75cdde31354fbffb4f25238ebd            0.0s
 => CACHED [2/5] WORKDIR /app                                                                                                     0.0s
 => CACHED [3/5] RUN echo -e "#!/bin/bash\necho test" > /app/test.sh                                                              0.0s
 => CACHED [4/5] RUN chmod 744 /app/test.sh                                                                                       0.0s
 => ERROR [5/5] RUN ls -al && exit 1                                                                                              0.2s
------                                                                                                                                 
 > [5/5] RUN ls -al && exit 1:
0.171 total 16
0.171 drwxr-xr-x    1 root     root          4096 May 31 05:21 .
0.171 drwxr-xr-x    1 root     root          4096 May 31 05:28 ..
0.171 -rwxr--r--    1 root     root            22 May 31 05:21 test.sh
------
Dockerfile:5
--------------------
   3 |     RUN echo -e "#!/bin/bash\necho test" > /app/test.sh
   4 |     RUN chmod 744 /app/test.sh
   5 | >>> RUN ls -al && exit 1
   6 |     ENTRYPOINT [ "/app/test.sh" ]
--------------------
ERROR: failed to solve: process "/bin/sh -c ls -al && exit 1" did not complete successfully: exit code: 1

明明文件存在且有权限，请问问题出在哪里？

原因分析 #

Alpine镜像默认只预装了轻量shell ash，没有安装bash。你的脚本开头用#!/bin/bash指定了解释器，容器执行脚本时找不到/bin/bash，就会抛出exec /app/test.sh: no such file or directory错误——这是Linux系统的常见行为：不是脚本文件不存在，而是脚本依赖的解释器不存在。

解决方案 #

有两种可行的解决方式：

方案1：改用Alpine默认的ash

把脚本的shebang改成#!/bin/sh，修改后的Dockerfile：

FROM alpine:latest
WORKDIR /app
RUN echo -e "#!/bin/sh\necho test" > /app/test.sh
RUN chmod 744 /app/test.sh
ENTRYPOINT [ "/app/test.sh" ]

方案2：在Alpine中安装bash

如果必须使用bash，可以在构建阶段通过apk安装：

FROM alpine:latest
WORKDIR /app
RUN apk add --no-cache bash
RUN echo -e "#!/bin/bash\necho test" > /app/test.sh
RUN chmod 744 /app/test.sh
ENTRYPOINT [ "/app/test.sh" ]

内容的提问来源于stack exchange，提问作者Ahmad