overlayfs on Fedora 24

overlayfs.md

OverlayFS on Fedora 24

Create a lower directory and upper directory

$ tree upper/ lower/
upper/
├── upper-file1
└── upper-subdir1
lower/
├── lower-file1
└── lower-subdir1

2 directories, 2 files

Merge:

$ sudo mount -t overlay overlay -o lowerdir=./lower,upperdir=./upper,workdir=./workdir ./merged

$ tree lower upper workdir merged/
lower
├── lower-file1
└── lower-subdir1
upper
├── upper-file1
└── upper-subdir1
workdir
└── work [error opening dir]
merged/
├── lower-file1
├── lower-subdir1
├── upper-file1
└── upper-subdir1

5 directories, 4 files

vagrant@localhost:~/work/merged $ touch lower-subdir1/lower-file1-from-overlay
vagrant@localhost:~/work/merged $ touch upper-subdir1/upper-file1-from-overlay

$ tree merged/
merged/
├── lower-file1
├── lower-subdir1
│   └── lower-file1-from-overlay
├── upper-file1
└── upper-subdir1
    └── upper-file1-from-overlay

2 directories, 4 files
vagrant@localhost:~/work $ tree upper/
upper/
├── lower-subdir1
│   └── lower-file1-from-overlay
├── upper-file1
└── upper-subdir1
    └── upper-file1-from-overlay

2 directories, 3 files
vagrant@localhost:~/work $ tree lower/
lower/
├── lower-file1
└── lower-subdir1

1 directory, 1 file

Notes

$ cat /proc/filesystems  | grep overlay
$ sudo modprobe overlay
$ lsmod | grep overlay
overlay                45056  0
$ cat /proc/filesystems | grep overlay
nodev   overlay

Link

• Role of overlayfs workdir

Issues

• coreos/bugs#989
• https://lwn.net/Articles/627232/
• https://www.google.com.au/q=overlayfs%20bugs