ubuntu 16.04安装的docker.io后，日志文件在什么位置呢?我的docker 的版本是Docker version 1.12.6, build 78d1802,在一个博文中发现这样的日志文件,请问这是怎么看出来的呢？

                2016-
                09-16T16:
                01:
                18.206540853+
                08:
                00 container kill b3256ef1400a7f6a6f242e377a77af5e25d3b12237c4ee7c2e9b31a5f6437868 (image=training/webapp, name=web5, signal=
                15
                ) 
                2016-
                09-16T16:
                01:
                38.212352224+
                08:
                00 container kill b3256ef1400a7f6a6f242e377a77af5e25d3b12237c4ee7c2e9b31a5f6437868 (image=training/webapp, name=web5, signal=
                9
                ) 
                2016-
                09-16T16:
                01:
                38.235021315+
                08:
                00 container die b3256ef1400a7f6a6f242e377a77af5e25d3b12237c4ee7c2e9b31a5f6437868 (exitCode=
                137, image=training/webapp, name=web5)