Mounted volume is empty inside container - docker

Question

I've got a docker-compose.yml like this:
db:
image: mongo:latest
ports:
- "27017:27017"
server:
image: artificial/docker-sails:stable-pm2
command: sails lift
volumes:
- server/:/server
ports:
- "1337:1337"
links:
- db
server/ is relative to the folder of the docker-compose.yml file. However when I docker exec -it CONTAINERID /bin/bash and check /server it is empty.
What am I doing wrong?

Answer 1

Aside from the answers here, it might have to do with drive sharing in Docker Setting. On Windows, I discovered that drive sharing needs to be enabled.
In case it is already enabled and you recently changed your PC's password, you need to disable drive sharing (and click "Apply") and re-enable it again (and click "Apply"). In the process, you will be prompted for your PC's new password. After this process, run your docker command (run or compose) again

Answer 2

Try using:
volumes:
- ./server:/server
instead of server/ -- there are some cases where Docker doesn't like the trailing slash.

Answer 3

As per docker volumes documentation,
https://docs.docker.com/engine/tutorials/dockervolumes/#/mount-a-host-directory-as-a-data-volume
The host-dir can either be an absolute path or a name value. If you
supply an absolute path for the host-dir, Docker bind-mounts to the
path you specify. If you supply a name, Docker creates a named volume
by that name

Answer 4

I had similar issue when I wanted to mount a directory from command line:
docker run -tid -p 5080:80 -v /d/my_project:/var/www/html/my_project nimmis/apache-php5
The container has been started successfully but the mounted directory was empty.
The reason was that the mounted directory must be under the user's home directory. So, I created a symlink under c:\Users\<username> that mounts to my project folder d:\my_project and mounted that one:
docker run -tid -p 5080:80 -v /c/Users/<username>/my_project/:/var/www/html/my_project nimmis/apache-php5

Answer 5

If you are using Docker for Mac then you need to go to:
Docker Desktop -> Preferences -> Resources -> File Sharing
and add the folder you intend to mount. See the screenshot:

Answer 6

I don't know if other people made the same mistake but the host directory path has to start from /home
So my msitake was that in my docker-compose I was WRONGLY specifying the following:
services:
myservice:
build: .
ports:
- 8888:8888
volumes:
- /Desktop/subfolder/subfolder2:/app/subfolder
When the host path should have been full path from /home. something like:
services:
myservice:
build: .
ports:
- 8888:8888
volumes:
- home/myuser/Desktop/subfolder/subfolder2:/app/subfolder

Answer 7

On Ubuntu 20.04.4 LTS, with Docker version 20.10.12, build e91ed57, I started observing a similar symptom with no apparent preceding action. After a docker-compose -p production-001 -f deploy/docker-compose.yml up -d --build command, with no changes to one of the services (production-001-volumeConsumingService is up-to-date), a part of the volumes stopped mounting.
# deploy/docker-compose.yml
version: "3"
services:
...
volumeConsumingService:
container_name: production-001-volumeConsumingService
hostname: production-001-volumeConsumingService
image: group/production-001-volumeConsumingService
build:
context: .
dockerfile: volumeConsumingService.Dockerfile
depends_on:
- anotherServiceDefinedEarlier
restart: always
volumes:
- ../data/certbot/conf:/etc/letsencrypt # mouning
- ../data/certbot/www:/var/www/certbot # not mounting
- ../data/www/public:/var/www/public # not mounting
- ../data/www/root:/var/www/root # not mounting
command: "/bin/sh -c 'while :; do sleep 6h & wait $${!}; nginx -s reload; done & nginx -g \"daemon off;\"'"
networks:
- default
- external
...
networks:
external:
name: routing
A workaround that seems to be working is to enforce a restart on the failing service immediately after the docker-compose -p production-001 -f deploy/docker-compose.yml up -d --build command:
docker-compose -p production-001 -f deploy/docker-compose.yml up -d --build && docker stop production-001-volumeConsumingService && docker start production-001-volumeConsumingService
In the case when the volumes are not mounted after a host reboot, adding a cron task to restart the service once should do.

Answer 8

In my case, the volume was empty because I did not use the right path format without quotes.
If you have a relative or absolute path with spaces in it, you do not need to use double quotes around the path, you can just use any path with spaces and it will be understood since docker-compose has the ":" as the delimiter and does not check spaces.
Ways that do not work (double quotes are the problem!):
volumes:
- "MY_PATH.../my server":/server
- "MY_PATH.../my server:/server" (I might have missed testing this, not sure!)
- "./my server":/server
- ."/my server":/server
- "./my server:/server"
- ."/my server:/server"
Two ways how you can do it (no double quotes!):
volumes:
- MY_PATH.../my server:/server
- ./my server:/server