docker overlay 文件系统原理

联合挂载

演示

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mkdir /lower{1,2,3} mkdir /upper /work /merged   mount -t overlay overlay -o lowerdir=/lower1:/lower2:/lower3,upperdir=/upper,workdir=/work /merged   df -h   touch /merged/123.txt   ls -l /upper/ ls -l /lower*   umount /merged   mount -t overlay overlay -o lowerdir=/lower1:/lower2:/lower3,workdir=/work /merged   touch /merged/456.txt   # touch: cannot touch '/merged/456.txt': Read-only file system

 

 

 

/merged 目录作为入口, /upper 是可读写目录, /lower* 是只读目录、对应的是镜像内的目录是不可修改的内容