Docker build step name cannot start with number - docker

Question

I'm building a docker image for a Sybase database. Docker build command fails because the name of the build step "server" cannot start with a number.
I have searched A LOT for a way to change the build step machine's name and my solution so far is to retry the build until I get a name that starts with a letter...
Step 1/7 : FROM my_image as docker_sybase_db
---> d266899b4eef
Step 2/7 : COPY *.zip /mnt/backup/
---> Using cache
---> 9e8e405848ce
Step 3/7 : COPY entrypoint.sh ~
---> Using cache
---> 5c0c923985db
Step 4/7 : ENV HOSTNAME docker_sybase_db
---> Using cache
---> f2b39a7280a0
Step 5/7 : RUN init_db.sh
---> Running in 0ae1a95b3203
Server name '0ae1a95b3203' begins with an illegal character. The first
character of a server name must be an alphabetic ascii character.
Error running command 'srvbuild -r /tmp/my_super_build.rs':
If I can't modify this old sybase init script, am I out of luck here ?
EDIT: Here is what I am trying to do
Create a database instance
Load a backup
Package that pre-loaded instance into a container.
Loading the backup takes a lot of time and this old database system requires the server name to start with a letter, not a number.

Answer 1

You could try and see if LolHens's idea of changing the hostname in the container namespace (during the docker build) works for you.
docker build . | tee >((grep --line-buffered -Po '(?<=^change-hostname ).*' || true) | \
while IFS= read -r id; do \
nsenter --target "$(docker inspect -f '{{ .State.Pid }}' "$id")"\
--uts hostname 'new-hostname'; \
done)
The docker build output is parsed to:
detect a "change-hostname" directive
do a nsenter, which runs a program in the UTS (UNIX Time Sharing) namespace, with a different hostname (different than the SHA-generated random one)
That means your RUN step should be:
RUN echo "change-hostname $(hostname)"; \
sleep 1; \
printf '%s\n' "$(hostname)" > /etc/hostname; \
printf '%s\t%s\t%s\n' "$(perl -C -0pe 's/([\s\S]*)\t.*$/$1/m' /etc/hosts)" "$(hostname)" > /etc/hosts; \
init_db.sh
That way, init_db.sh should run in an intermediate container with a different hostname (one you do have control over, and which would not start with a number).