[doc] docker cp gives surprising result with tmpfs #22020
Description
When tmpfs is mounted on a container, docker cp copies the content of the underlying directory rather than the content of the tmpfs.
I'm not sure this is expected result or not.
But even if this is expected result, I think it is worth explictly mentioning this on the documentation.
Output of docker version:
Client:
Version: 1.11.0
API version: 1.23
Go version: go1.5.4
Git commit: 4dc5990
Built: Thu Apr 14 05:05:19 2016
OS/Arch: linux/amd64
Server:
Version: 1.11.0
API version: 1.23
Go version: go1.5.4
Git commit: 4dc5990
Built: Thu Apr 14 05:05:19 2016
OS/Arch: linux/amd64
Output of docker info:
Containers: 58
Running: 1
Paused: 0
Stopped: 57
Images: 294
Server Version: 1.11.0
Storage Driver: overlay
Backing Filesystem: extfs
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge null host
Kernel Version: 4.2.0-30-generic
Operating System: Ubuntu 15.10
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 7.796 GiB
Name: ip-172-31-8-43
ID: 5HJM:SQPO:3NEM:ZYX7:3LME:WIHB:E3BN:RNMZ:6K4F:JCQ6:UY2Z:CR26
Docker Root Dir: /var/lib/docker
Debug mode (client): false
Debug mode (server): true
File Descriptors: 17
Goroutines: 43
System Time: 2016-04-14T05:11:22.886582661Z
EventsListeners: 0
Registry: https://index.docker.io/v1/
WARNING: No swap limit support
Additional environment details (AWS, VirtualBox, physical, etc.):
AWS (not related to this issue)
Steps to reproduce the issue:
On Terminal 1:
host$ (cd DOCKER_SRC_DIR; make shell)
root@78e5073cf591:/go/src/github.com/docker/docker# ls /tmp
root@78e5073cf591:/go/src/github.com/docker/docker# echo foo > /tmp/foo.txt
root@78e5073cf591:/go/src/github.com/docker/docker# ls /tmp
foo.txt
On Terminal 2:
host$ docker cp 78e5:/tmp xtmp
host$ ls xtmp
pip_build_root/ tmp.KrRLOzisMN/ tmp.bRFDLAOQtb/
Describe the results you received:
pip_build_root/ tmp.KrRLOzisMN/ tmp.bRFDLAOQtb/
Describe the results you expected:
foo.txt
Additional information you deem important (e.g. issue happens only occasionally):
hack/dindmounts/tmpon a container and causes this surprising result.- Even reproducible by running
docker run -it --tmpfs=/tmp --rm busyboxinstead ofmake shell. - Not reproducible by just running
docker run -it --rm busyboxinstead ofmake shell. - Reproducible with Docker 1.10.3 + AUFS. So this is not new to 1.11 nor specific to Overlay.