I'm new to docker. I've a very simple Dockerfile but when I try to build an image from this Dockerfile, i get "cannot normalize nothing" error.
FROM alpine:latest
RUN apk add vim
CMD ["bash"]
WORKDIR $HOME
For building the image, I use the following command:
$ docker build -t aamirglb/test:1.0 .
I used Play With Docker (PWD) to test this script and here is the output.
If I comment out WORKDIR $HOME line, the build is successful.
Any help in understanding this error will be highly appreciated.
Thanks in advance.
CodePudding user response：
For those that can't reproduce, this error does not happen with buildkit:
$ docker build -t test-workdir -f df.workdir-empty .
[ ] Building 0.2s (6/6) FINISHED
=> [internal] load build definition from df.workdir-empty 0.0s
=> => transferring dockerfile: 43B 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 34B 0.0s
=> [internal] load metadata for docker.io/library/alpine:latest 0.0s
=> [1/3] FROM docker.io/library/alpine:latest 0.0s
=> CACHED [2/3] RUN apk add vim 0.0s
=> exporting to image 0.0s
=> => exporting layers 0.0s
=> => writing image sha256:cadafef9a77c95b1b32499bcc1beba016ff0a7071710a1c37eb4e5f32e5d1c94 0.0s
=> => naming to docker.io/library/test-workdir 0.0s
But if you build with the classic builder, the error does appear:
$ DOCKER_BUILDKIT=0 docker build -t test-workdir -f df.workdir-empty .
Sending build context to Docker daemon 23.04kB
Step 1/4 : FROM alpine:latest
---> 14119a10abf4
Step 2/4 : RUN apk add vim
---> Running in a286e7f3107a
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/community/x86_64/APKINDEX.tar.gz
(1/5) Installing xxd (8.2.4708-r0)
(2/5) Installing lua5.3-libs (5.3.6-r0)
(3/5) Installing ncurses-terminfo-base (6.2_p20210612-r0)
(4/5) Installing ncurses-libs (6.2_p20210612-r0)
(5/5) Installing vim (8.2.4708-r0)
Executing busybox-1.33.1-r3.trigger
OK: 26 MiB in 19 packages
Removing intermediate container a286e7f3107a
---> acdd6e1963db
Step 3/4 : CMD ["bash"]
---> Running in 6deb306db96a
Removing intermediate container 6deb306db96a
---> 960f0de2f376
Step 4/4 : WORKDIR $HOME
cannot normalize nothing
And before you get your hopes up, workdir in the buildkit example is not set to the user's home directory:
$ docker inspect test-workdir:latest --format '{{.Config.WorkingDir}}'
/
So first, what does cannot normalize nothing mean? Normalizing is the process of taking a path like /.//some/../path and turning that into /path, cleaning the string of unnecessary content and converting it into a uniform path. That process doesn't work on nothing, it needs a string or value, or at least the classic builder does (buildkit seems to have a sensible default).
Why doesn't $HOME default to /root? Because that variable was never set in docker. The only environment variable defined in there is a path:
$ docker inspect test-workdir:latest --format '{{.Config.Env}}'
[PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin]
When you launch a shell like /bin/sh in the container, that shell is what is defining $HOME and various other variables:
$ docker run -it --rm test-workdir /bin/sh
/ # env
HOSTNAME=c68d4370e413
SHLVL=1
HOME=/root
TERM=xterm
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
PWD=/
Since there was no ENV or ARG to set $HOME, you cannot use it in the WORKDIR step.