Capture ouput of docker build into a log file?

General Discussions
#1

I’d like to be able to capture the output of a docker build task into a log file.

I assumed that docker build <arguments> --progress=plain >> docker-build.log would suffice however the resulting file is empty.

I’ve tried to see if docker keeps a log file anywhere of the output from builds however I’ve not been able to find any reference to this.

#2

That’s because the output is not on the standard output but the standard error stream. So you can try this to redirect everything into the file:

docker build --no-cache --progress=plain  . &> build.log

or just redirect standard error if you think there should be some other output to show in the terminal

docker build --no-cache --progress=plain  . 2> build.log

Or you can use tee to show the logs and also save it to a file

docker build --no-cache --progress=plain . 2>&1 | tee build.log

If you want to append new logs and not to overwrite on every build, use >> for the redirection as you did originally. If you choose the version with tee, you can use tee -a to append the new logs

3 Likes
#3

That worked perfectly.

Thank you!

#4

I am glad it helped.

When I came back to see your response I noticed I left the --no-cache option in all of my commands. That option is not required of course. You can remove it.