How can I use a several line command in a Dockerfile in order to create a file within the resulting-CodePudding

I'm following installation instructions for RedhawkSDR, which rely on having a Centos7 OS. Since my machine uses Ubuntu 22.04, I'm creating a Docker container to run Centos7 then installing RedhawkSDR in that.

One of the RedhawkSDR installation instructions is to create a file with the following command:

cat<<EOF|sed 's@LDIR@'`pwd`'@g'|sudo tee /etc/yum.repos.d/redhawk.repo
[redhawk]
name=REDHAWK Repository
baseurl=file://LDIR/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhawk
EOF

How do I get a Dockerfile to execute this command when creating an image?

(Also, although I can see that this command creates the file /etc/yum.repos.d/redhawk.repo, which consists of the lines from [redhawk] to gpgkey=...., I have no idea how to parse this command and understand exactly why it does that...)

CodePudding user response：

Using the text editor of your choice, create the file on your local system. Remove the word sudo from it; give it an additional first line #!/bin/sh. Make it executable using chmod x create-redhawk-repo.

Now it is an ordinary shell script, and in your Dockerfile you can just RUN it.

COPY create-redhawk-repo ./
RUN ./create-redhawk-repo

But! If you look at what the script actually does, it just writes a file into /etc/yum.repos.d with a LDIR placeholder replaced with some other directory. The filesystem layout inside a Docker image is fixed, and there's no particular reason to use environment variables or build arguments to hold filesystem paths most of the time. You could use a fixed path in the file

[redhawk]
name=REDHAWK Repository
baseurl=file:///redhawk-yum/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhawk

and in your Dockerfile, just COPY that file in as-is, and make sure the downloaded package archive is in that directory. Adapting the installation instructions:

ARG redhawk_version=3.0.1
RUN wget https://github.com/RedhawkSDR/redhawk/releases/download/$redhawk_version/\
redhawk-yum-$redhawk_version-el7-x86_64.tar.gz \
 && tar xzf redhawk-yum-$redhawk_version-el7-x86_64.tar.gz \
 && rm redhawk-yum-$redhawk_version-el7-x86_64.tar.gz \
 && mv redhawk-yum-$redhawk_version-el7-x86_64 redhawk-yum \
 && rpm -i redhawk-yum/redhawk-release*.rpm
COPY redhawk.repo /etc/yum.repos.d/

Remember that, in a Dockerfile, you are root unless you've switched to another USER (and in that case you can use USER root to switch back); you do not need generally sudo in Docker at all, and can just delete sudo where it appears in these instructions.

CodePudding user response：

How do I get a Dockerfile to execute this command when creating an image?

Just use printf and run this command as single line:

FROM image_name:image_tag
ARG LDIR="/default/folder/if/argument/not/set"

# if container has sudo command and default user is not root
# you should choose this variant
RUN printf '[redhawk]\nname=REDHAWK Repository\nbaseurl=file://%s/\nenabled=1\ngpgcheck=1\ngpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhawk\n' "$LDIR" | sudo tee /etc/yum.repos.d/redhawk.repo

# if default container user is root this command without piping may be used
RUN printf '[redhawk]\nname=REDHAWK Repository\nbaseurl=file://%s/\nenabled=1\ngpgcheck=1\ngpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhawk\n' "$LDIR" > /etc/yum.repos.d/redhawk.repo

Where LDIR is an argument and docker build process should be run like:

docker build ./ --build-arg LDIR=`pwd`