Support `tmpfs-size` and `tmpfs-mode` in compose-file

[luochen1990]

@thaJeztah suggests to use a --mount option as an workaround of --shm-size like that:

docker service create \
  --name tmpfstest \
  --mount type=tmpfs,dst=/dev/shm,tmpfs-size=1000000000 \
  --tty \
  debian:stretch-slim cat

But I can't find anything about how to set the tmpfs-size in the doc about volume-long-syntax. I think this feature should be supported.

[thaJeztah]

Thanks for opening this!

/cc @vdemeester @dnephin

[glyif]

What are you peeps thinking the docker-compose syntax should look like?

Something like this?

volumes:
    - type: tmpfs
       size: 10000

[dnephin]

I think it should match the existing types (bind, volume):

volumes:
 - type: tmpfs
   target: /tmp
   tmpfs:
     size: 10000

[vdemeester]

Sounds like it's been fixed by #808

[ypresto]

Looks tmpfs-mode one is not implemented yet. Only tmpfs: size: ... is implemented.

[thaJeztah]

@ypresto could you open a new issue, so that we don't loose sight?

[mterron]

Actually the supported mount options are the same as the Linux default mount flags. If you do not specify any options, the systems uses the following options: rw,noexec,nosuid,nodev,size=65536k, it's just that the documentation is incorrect.

This actually does what it's supposed to:

version: "2.4"
services:
  my_app:
    image: my_app
    read_only: true
    restart: always
    tmpfs:
      - /run:mode=770,size=1k,uid=200,gid=10000

It'll set /run mode to 770 with a 1k size limit and owned by uid 200 and gid 10000