github.com/feiyang21687/docker@v1.5.0/docs/sources/terms/filesystem.md (about)

     1  page_title: File Systems
     2  page_description: How Linux organizes its persistent storage
     3  page_keywords: containers, files, linux
     4  
     5  # File System
     6  
     7  ## Introduction
     8  
     9  ![](/terms/images/docker-filesystems-generic.png)
    10  
    11  In order for a Linux system to run, it typically needs two [file
    12  systems](http://en.wikipedia.org/wiki/Filesystem):
    13  
    14  1. boot file system (bootfs)
    15  2. root file system (rootfs)
    16  
    17  The **boot file system** contains the bootloader and the kernel. The
    18  user never makes any changes to the boot file system. In fact, soon
    19  after the boot process is complete, the entire kernel is in memory, and
    20  the boot file system is unmounted to free up the RAM associated with the
    21  initrd disk image.
    22  
    23  The **root file system** includes the typical directory structure we
    24  associate with Unix-like operating systems:
    25  `/dev, /proc, /bin, /etc, /lib, /usr,` and `/tmp` plus all the configuration
    26  files, binaries and libraries required to run user applications (like bash,
    27  ls, and so forth).
    28  
    29  While there can be important kernel differences between different Linux
    30  distributions, the contents and organization of the root file system are
    31  usually what make your software packages dependent on one distribution
    32  versus another. Docker can help solve this problem by running multiple
    33  distributions at the same time.
    34  
    35  ![](/terms/images/docker-filesystems-multiroot.png)