Dockerfile works when every line run interactively, but fails using docker build

Question

I have a simple Dockerfile that downloads the node.js source tarball, checksums it, extracts it, builds and installs it. The checksum works when manually run in an interactive docker container, but fails when running the exact same commands when building a Dockerfile.

Works:

docker run -i -t ubuntu:12.04 /bin/bash

cd /tmp

apt-get update -y

apt-get install wget build-essential automake -y

wget http://nodejs.org/dist/latest/node-v0.10.26.tar.gz

wget http://nodejs.org/dist/latest/SHASUMS256.txt

sha256sum -c SHASUM256.txt 2>&1|grep -qs OK

tar -xvf node-v0.10.26.tar.gz && cd node-v0.10.26

./configure && make && make install

Doesn't work:

sudo docker build -t="my_docker_node_image_01" .

Error is:

sudo docker build -t="my_docker_node_image_01" .                                        
Uploading context 7.168 kB
Uploading context 
Step 0 : FROM ubuntu:12.04
 ---> 9cd978db300e
Step 1 : RUN cd /tmp
 ---> Using cache
 ---> 0467ad75bbd6
Step 2 : RUN apt-get update -y
 ---> Using cache
 ---> d2933f250090
Step 3 : RUN apt-get install wget build-essential automake -y
 ---> Using cache
 ---> e8a71b28782a
Step 4 : RUN wget http://nodejs.org/dist/latest/node-v0.10.26.tar.gz
 ---> Using cache
 ---> bae7de7b46f7
Step 5 : RUN wget http://nodejs.org/dist/latest/SHASUMS256.txt
 ---> Using cache
 ---> 245f6b6ceb84
 ---> 77532c879864
Step 6 : RUN sha256sum -c SHASUM256.txt 2>&1|grep -qs OK
 ---> Running in 77765e80f55b
2014/04/22 22:27:32 The command [/bin/sh -c sha256sum -c SHASUM256.txt 2>&1|grep -qs OK] returned a non-zero code: 1

I tried adding less SHASUMS256.txt to the Dockerfile just to confirm that file is successfully downloaded uncorrupted, and it is, but still getting the error anyway.

I'm not sure how to troubleshoot this since normally I would just manually run all the steps in an interactive container to see what goes wrong. Any suggestions much appreciated.

Why are you piping the result to grep? sha256sum might write to the console, but should set the proper exit code if the file is OK. Also, can you echo the sum from SHASUM256.txt and the calculated sum from node.gz? I couldn't get this to fail. — Todd
Thanks, the problem is that every line in SHASUMS256.txt that doesn't checksum gets sent to stderr, resulting in non-zero exit code and the build failing even if one line does successfully checksum. The solution I thought would work is to merge stderr with stdout, pipe it to grep, filter the single line that checksums (OK), and suppress all output except exit codes. That would result in 0 if OK is present, 1 if not. It works in interactive mode, but not non-interactive Dockerfile build. Trying to figure out why. — Kurtosis

Todd Todd · Accepted Answer · 2014-04-24T19:15:56

I think I figured this out and it's just a typo, at least when I cut and paste your commands above! You download SHASUMS256.txt but test against a file called SHASUM256.txt (missing the S). Because you throw away the output and pipe it to grep, you weren't seeing that error.

$ sha256sum -c SHASUM256.txt 
sha256sum: SHASUM256.txt: No such file or directory

$ sha256sum -c SHASUM256.txt 2>&1|grep -qs OK
$ echo $?
1

Doing an echo $? tells you the return code of the last command executed (in this case 1). By correcting the file, it works for me now:

 $ sha256sum -c SHASUMS256.txt 2>&1|grep -qs OK
 $ echo $?
 0

Dockerfile works when every line run interactively, but fails using docker build

1 Answers