volumes in docker compose can't see files if mounted from outside home directory

Docker Engine Compose
1

Dear all,
I use docker quite a lot but this is the first time I see problem like follows:
System: Ubuntu server.
SELinux: disabled
Docker: 20.10.24, build 297e128 (installed with system)
compose.yaml:

version: ‘1’
services:
test:
image: busybox
volumes:
- /data/testdir:/testdir:z
command: tail -F anything

In above example no data stored in /data/testdir is visible inside running container. After copying data to /home/user and changing compose.yaml to

version: ‘1’
services:
test:
image: busybox
volumes:
- /home/user/testdir:/testdir:z
command: tail -F anything

data becomes visible. Permissions are still the same. Docker-compose runned as root. Data permissons 777. What is going on?

2

Please remove the :z at the end of your volume bind and try again.

3

No changes. The compose.yaml I provided here is simplified file for test purpose. In reality I need to share local dir between containers (that’s the reason for :z at the end). But no matter if it’s there or not - still it only works when dealing with dirs within my home dir. If the data is located in root file system - it doesn’t.

4

Though, you do know those are only relevant with selinux, right?
https://docs.docker.com/storage/bind-mounts/#configure-the-selinux-label

Please share the output of following commands:

docker info

docker version

dpkg -l | grep docker

snap list docker
5

Well… No. I didn’t knew that. Good to know.

> docker info
Client:
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc., v0.10.4)
  compose: Docker Compose (Docker Inc., v2.17.2)

Server:
 Containers: 3
  Running: 3
  Paused: 0
  Stopped: 0
 Images: 6
 Server Version: 20.10.24
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 2806fc1057397dbaeefbea0e4e17bddfbd388f38
 runc version:
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: default
  cgroupns
 Kernel Version: 5.15.0-88-generic
 Operating System: Ubuntu Core 22
 OSType: linux
 Architecture: x86_64
 CPUs: 4
 Total Memory: 7.538GiB
 Name: donpedro
 ID: XXXX.XXXX....XXXX.XXXX
 Docker Root Dir: /var/snap/docker/common/var-lib-docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

> docker version
Client:
 Version:           20.10.24
 API version:       1.41
 Go version:        go1.20.7
 Git commit:        297e128
 Built:             Wed Aug 23 20:54:23 2023
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server:
 Engine:
  Version:          20.10.24
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.20.7
  Git commit:       5d6db84
  Built:            Wed Aug 23 20:55:00 2023
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.6.20
  GitCommit:        2806fc1057397dbaeefbea0e4e17bddfbd388f38
 runc:
  Version:          1.1.5
  GitCommit:
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

> dpkg -l | grep docker
-- empty --

> snap list docker
Name    Version   Rev   Tracking       Publisher   Notes
docker  20.10.24  2904  latest/stable  canonical✓  -
6

Please, format your post according to the following guide: How to format your forum posts
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Regarding your issue, as @meyay suspected, you installed Docker from snap which is in our opinion is a bad idea. Install it as it is described in the official documentation.

Snap runs packages in a container which is really bad for Docker. I whish I could make canonical stop publishing that snap package.

1 Like
7

I’m so with you! That makes it so hard for newbes to find what is going on.
Thanks for your help!