Arch Linux

jono

Member

Registered: 2012-01-03

Posts: 13

[SOLVED] df errors in Docker

Steps to reproduce:
>  docker run ubuntu df -l /
df: no file systems processed

I have noticed that when using Arch as a host my docker containers mount / differently then on my Ubuntu system.

I am wondering if anyone knows why because I have a program (MogileFS) that depends on local filesystems and is failing when Dockerized in Arch.
Here is my full experience.

Using Ubuntu 14 host:

>  uname -av
Linux digitus 3.13.0-54-generic #91-Ubuntu SMP Tue May 26 19:15:08 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
>  docker --version
Docker version 1.6.2, build 7c8fca2
>  docker run ubuntu df
Filesystem                                             1K-blocks     Used Available Use% Mounted on
rootfs                                                 230157492 99560148 118882992  46% /
none                                                   230157492 99560148 118882992  46% /
tmpfs                                                    8193784        0   8193784   0% /dev
shm                                                        65536        0     65536   0% /dev/shm
/dev/disk/by-uuid/e86cc0f4-36,,,         230157492 99560148 118882992  46% /etc/hosts
tmpfs                                                    8193784        0   8193784   0% /proc/kcore
tmpfs                                                    8193784        0   8193784   0% /proc/latency_stats
tmpfs                                                    8193784        0   8193784   0% /proc/timer_stats
>  docker run ubuntu df -l /
Filesystem     1K-blocks     Used Available Use% Mounted on
none           230157492 99561624 118881516  46% /

Using Arch Linux host:

>  uname -av               
Linux ageras 4.0.5-1-ARCH #1 SMP PREEMPT Sat Jun 6 18:37:49 CEST 2015 x86_64 GNU/Linux
>  docker --version
Docker version 1.6.2, build 7c8fca2
>  docker run ubuntu df   
Filesystem                                                                         1K-blocks     Used Available Use% Mounted on
/dev/mapper/docker-254:0-4457836-a4a69a,,,,71744b1  10190136   236036   9413428   3% /
tmpfs                                                                                   3985956        0   3985956   0% /dev
shm                                                                                      65536        0     65536   0% /dev/shm
/dev/mapper/cryptAntergos                                              107140128 14880856  86793776  15% /etc/hosts
tmpfs                                                                                  3985956        0   3985956   0% /proc/kcore
tmpfs                                                                                    3985956        0   3985956   0% /proc/timer_stats
>  docker run ubuntu df -l /
df: no file systems processed
>  docker run ubuntu df -l 
Filesystem                1K-blocks     Used Available Use% Mounted on
tmpfs                       3985956        0   3985956   0% /dev
shm                           65536        0     65536   0% /dev/shm
/dev/mapper/cryptAntergos 107140128 14883984  86790648  15% /etc/hosts
tmpfs                       3985956        0   3985956   0% /proc/kcore
tmpfs                       3985956        0   3985956   0% /proc/timer_stats

Last edited by jono (2015-06-24 04:08:29)

jono

Member

Registered: 2012-01-03

Posts: 13

Re: [SOLVED] df errors in Docker

I want to delete this post but I cant figure out how to on this forum.

I found the problem was that Arch is causing Docker to use the Device Mapper storage driver. This makes it such that containers need to mount a remote filesystem for the root partition. This of course causes 'df -l /' to fail.

Ubuntu was using AUFS as its filesystem that uses a local root partition.

Spider.007

Member

Registered: 2004-06-20

Posts: 1,175

Re: [SOLVED] df errors in Docker

You cannot delete this post, but thanks for adding the solution. You should edit the first post and mark this thread as solved as well

Reason

Member

From: TN, USA

Registered: 2012-06-25

Posts: 7

Re: [SOLVED] df errors in Docker

Just to add to this discussion a little bit: docker picks its 'storage driver' out of a priority list: "aufs,btrfs,devicemapper,vfs,overlay", picking the first available driver.

AUFS isn't in the mainline kernel, but is in ubuntu's patched kernel.

You can override this behavior with "-s <driver>" to force docker to use one driver over another.