Conclusion

--When using Docker on NILFS2 filesystem, set the storage driver to "devicemapper".

`/etc/docker/daemon.json`


{
  "storage-driver": "devicemapper"
}

background

The scariest thing about using the Raspberry PI 3b regularly is that the SD card suddenly breaks one day. So I converted/(rootfs) to NILFS, but docker didn't work well, so make a note of it.

Our environment

Operates only with a 32GB micro SD card. Set/dev/mmcblk0p2 to NILFS2.

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 5.4.79-v7+ #1373 SMP Mon Nov 23 13:22:33 GMT 2020 armv7l GNU/Linux
pi@raspberrypi:~ $ df -hT
File system type size used remaining used%Mount position
udev           devtmpfs   424M     0  424M    0% /dev
tmpfs          tmpfs       93M  8.7M   84M   10% /run
/dev/mmcblk0p2 nilfs2      30G   19G  9.6G   66% /
tmpfs          tmpfs      463M  4.0K  463M    1% /dev/shm
tmpfs          tmpfs      5.0M  4.0K  5.0M    1% /run/lock
tmpfs          tmpfs      463M     0  463M    0% /sys/fs/cgroup
/dev/mmcblk0p1 vfat       253M   68M  185M   27% /boot
tmpfs          tmpfs       93M  4.0K   93M    1% /run/user/1000
pi@raspberrypi:~ $ docker version
Client:
 Version:           18.09.1
 API version:       1.39
 Go version:        go1.11.6
 Git commit:        4c52b90
 Built:             Fri, 13 Sep 2019 10:45:43 +0100
 OS/Arch:           linux/arm
 Experimental:      false

Server:
 Engine:
  Version:          18.09.1
  API version:      1.39 (minimum version 1.12)
  Go version:       go1.11.6
  Git commit:       4c52b90
  Built:            Fri Sep 13 09:45:43 2019
  OS/Arch:          linux/arm
  Experimental:     false

Tried storage driver

--overlay2 (default) ... △ (hello-world, busybox works, but ubuntu and large images (with multiple layers) cannot be pulled. --overlay ... × (It is said that permission is denied and it does not work at all) --vfs ... ○, but the performance is the worst. --devicemapper ... ◎. It seems to work fine.

How does devicemapper work?

It seems that a huge sparse file is created in advance, and it is cut out and used. It's refreshing to see 100G files on an SD card that is only 32GB. w

root@raspberrypi:/var/lib/docker# ls -lh devicemapper/devicemapper/data 
-rw-------1 root root 100G December 29 08:34 devicemapper/devicemapper/data

Remaining items

--Memoized the procedure to make root of Raspbian OS NILFS. (I was addicted to various places unexpectedly)

Docker on NILFS2 filesystem (for raspbianOS)