#拉一个nginx镜像
[root@localhost ~]# docker pull nginx

#以后台模式启动nginx镜像容器实例
[root@localhost ~]# docker run -d nginx

#获取正在运行容器的ID
[root@localhost ~]# docker ps -all
CONTAINER ID   IMAGE     COMMAND                  CREATED          STATUS          PORTS     NAMES
be2f9901e364   nginx     "/docker-entrypoint.…"   35 seconds ago   Up 32 seconds   80/tcp    nifty_agnesi

#进入容器：
[root@localhost ~]# docker exec -it be2f9901e364

#检查文件系统信息
root@be2f9901e364:/# df -h
Filesystem           Size  Used Avail Use% Mounted on
overlay              589G   74G  490G  14% /
tmpfs                 64M     0   64M   0% /dev
tmpfs                7.8G     0  7.8G   0% /sys/fs/cgroup
shm                   64M     0   64M   0% /dev/shm
/dev/mapper/vg-root  589G   74G  490G  14% /etc/hosts
tmpfs                7.8G     0  7.8G   0% /proc/asound
tmpfs                7.8G     0  7.8G   0% /proc/acpi
tmpfs                7.8G     0  7.8G   0% /proc/scsi
tmpfs                7.8G     0  7.8G   0% /sys/firmware

#进入一个 tmpfs 目录
root@be2f9901e364:/proc/asound# cd /sys/fs/cgroup

root@be2f9901e364:/sys/fs/cgroup# ls
blkio  cpu,cpuacct  cpuset   freezer  memory   net_cls,net_prio  perf_event  systemd
cpu    cpuacct	    devices  hugetlb  net_cls  net_prio		 pids