本文的运行环境为Centos 7.3，Docker与Kubernetes的安装方式见
最近在整理Docker和Kubernetes中的日志与相关配置，在尝试通过/etc/docker/daemon.json配置Docker的log-driver参数，遇到了Docker无法启动的错误。
配置信息如下
{ "log-driver": "json-file", "log-opts": { "max-size": "1m", "max-file": "5" }} 错误提示如下
[root@devops-101 ~]# journalctl -amu docker-- Logs begin at Thu 2018-08-30 08:28:53 CST, end at Thu 2018-08-30 08:47:53 CST. --Aug 30 08:29:07 devops-101 systemd[1]: Starting Docker Application Container Engine...Aug 30 08:29:08 devops-101 dockerd-current[1102]: unable to configure the Docker daemon with file /etc/docker/daemon.json: the following directives are specified both as a flag and in the configuration file: log-driAug 30 08:29:08 devops-101 systemd[1]: docker.service: main process exited, code=exited, status=1/FAILUREAug 30 08:29:08 devops-101 systemd[1]: Failed to start Docker Application Container Engine.
这个含义应该是Docker启动的时候传入了命令行参数，同时也指定了配置文件，两个配置发生了冲突。那么就查看一下Docker服务启动文件。
[root@devops-101 ~]# vim /usr/lib/systemd/system/docker.service [Service]Type=notifyNotifyAccess=allEnvironmentFile=-/run/containers/registries.confEnvironmentFile=-/etc/sysconfig/dockerEnvironmentFile=-/etc/sysconfig/docker-storageEnvironmentFile=-/etc/sysconfig/docker-networkEnvironment=GOTRACEBACK=crashEnvironment=DOCKER_HTTP_HOST_COMPAT=1Environment=PATH=/usr/libexec/docker:/usr/bin:/usr/sbinExecStart=/usr/bin/dockerd-current \ --add-runtime docker-runc=/usr/libexec/docker/docker-runc-current \ --default-runtime=docker-runc \ --exec-opt native.cgroupdriver=systemd \ --userland-proxy-path=/usr/libexec/docker/docker-proxy-current \ --init-path=/usr/libexec/docker/docker-init-current \ --seccomp-profile=/etc/docker/seccomp.json \ $OPTIONS \ $DOCKER_STORAGE_OPTIONS \ $DOCKER_NETWORK_OPTIONS \ $ADD_REGISTRY \ $BLOCK_REGISTRY \ $INSECURE_REGISTRY \ $REGISTRIES
可以看到启动的时候会从/etc/sysconfig/docker中获取环境变量。
[root@devops-101 ~]# vim /etc/sysconfig/docker# /etc/sysconfig/docker# Modify these options if you want to change the way the docker daemon runsOPTIONS='--selinux-enabled --log-driver=journald --signature-verification=false'if [ -z "${DOCKER_CERT_PATH}" ]; then DOCKER_CERT_PATH=/etc/dockerfi 可以看到参数中默认了--log-driver=journald，把这一段删掉就可以了。重启之后，就可以在/var/log/containers下看到容器产生的日志文件了。
[root@devops-101 containers]# pwd/var/log/containers[root@devops-101 containers]# ls coredns-78fcdf6894-52gp9_kube-system_coredns-6eea955dfaad8027b9382a9911817057c917e3187dee41502dcd687d8de18729.logcoredns-78fcdf6894-mkvqn_kube-system_coredns-16ed56195ca55c613dec218cfd57c647f8bbe0341b38c446210db98d6ab78f3c.logetcd-devops-101_kube-system_etcd-42717aa4eda15817f05f35b68f84306ab83fd3f397426c2c9b47d71ebf61942b.logkube-apiserver-devops-101_kube-system_kube-apiserver-0df17d68a3b1742e9e34620b759b4617f1949bbe2d826b03216419b6994db42c.logkube-controller-manager-devops-101_kube-system_kube-controller-manager-ee1743e4a4c0114da1cfb32bd78f4f7a576bfc021aacd943e92d2e09cb41116d.logkube-flannel-ds-7sgps_kube-system_install-cni-92ce6121a1a5456752f502c07ae324676e0d1297261dad266b385a5e6522852c.logkube-flannel-ds-7sgps_kube-system_kube-flannel-e6eb715062314f175d9fbaa52323f93eeffbb9fa16eed95797c9950884f68b73.logkube-proxy-79gws_kube-system_kube-proxy-8ce96b3b403d0f7231ca6a004bfec162a093f85ea940867264f50530846d3e0a.logkube-scheduler-devops-101_kube-system_kube-scheduler-c7ce974eedbc3119320e729310e1b905f65df84dbe46624918dfc33628d9a864.log