Error loading key "/root/.ssh/id_rsa": invalid format

$ docker login -u gitlab-ci-token -p $CI_BUILD_TOKEN $CI_REGISTRY107WARNING! Using --password via the CLI is insecure. Use --password-stdin.108WARNING! Your password will be stored unencrypted in /root/.docker/config.json.109Configure a credential helper to remove this warning. See110 Succeeded112$ mkdir -p ~/.ssh && touch ~/.ssh/known_hosts113$ echo "$SERVER_SSH" | tr -d '\r' > ~/.ssh/id_rsa114$ chmod 700 ~/.ssh115$ chmod 600 ~/.ssh/id_rsa116$ [[ -f ./dockerenv ]] && echo -e "Host *\n\tStrickHostKeyChecking no\n\n" > ~/.ssh/config117$ which ssh-agent || ( apt-get update -y && apt-get install openssh-client -y )118/usr/bin/ssh-agent119$ eval "$(ssh-agent -s)"120Agent pid 30121$ ssh-add ~/.ssh/id_rsa122Error loading key "/root/.ssh/id_rsa": invalid format124Cleaning up file based variables00:00126ERROR: Job failed: exit code 1