the kernel version check in the overlay2 driver appears to be unnecessarily restrictive for the case where the overlay driver support for multiple lower dirs has been backported, as it has in EL 7. from what i can tell, the 3.10 kernel in EL7 does support multiple lower directories, so should be supported. Here's my replication of the kernel docs' description of support for this feature in an EL 7.2 test-kitchen VM:
[root@docker-centos-72 ~]# uname -r
3.10.0-327.el7.x86_64
[root@docker-centos-72 ~]# mkdir -pv /lower1 /lower2 /lower3 /merged
mkdir: created directory ‘/lower1’
mkdir: created directory ‘/lower2’
mkdir: created directory ‘/lower3’
mkdir: created directory ‘/merged’
[root@docker-centos-72 ~]# touch /lower1/1.txt /lower2/2.txt /lower3/3.txt
[root@docker-centos-72 ~]# mount -t overlay overlay -olowerdir=/lower1:/lower2:/lower3 /merged
[root@docker-centos-72 ~]# ls /merged/
1.txt 2.txt 3.txt
but on starting the daemon, it fails with error: time="2016-06-28T05:17:20.646178896Z" level=fatal msg="Error starting daemon: error initializing graphdriver: driver not supported".
Output of docker version:
Client:
Version: 1.12.0-rc2
API version: 1.24
Go version: go1.6.2
Git commit: 906eacd
Built:
OS/Arch: linux/amd64
Experimental: true
Server:
Version: 1.12.0-rc2
API version: 1.24
Go version: go1.6.2
Git commit: 906eacd
Built:
OS/Arch: linux/amd64
Experimental: true
Output of docker info:
[root@docker-centos-72 ~]# docker info
Cannot connect to the Docker daemon. Is the docker daemon running on this host?
Additional environment details (AWS, VirtualBox, physical, etc.):
tested in VirtualBox
Steps to reproduce the issue:
- install docker 1.12 rc on EL 7.2
- run docker daemon with
--storage-driver=overlay2
- observe error
Describe the results you received:
docker daemon start failure due to initialization check for kernel version >= 4.0 when running docker with overlay2 storage driver on EL 7.2
Describe the results you expected:
success running docker with overlay2 storage driver on EL 7.2
the kernel version check in the overlay2 driver appears to be unnecessarily restrictive for the case where the overlay driver support for multiple lower dirs has been backported, as it has in EL 7. from what i can tell, the 3.10 kernel in EL7 does support multiple lower directories, so should be supported. Here's my replication of the kernel docs' description of support for this feature in an EL 7.2 test-kitchen VM:
but on starting the daemon, it fails with error:
time="2016-06-28T05:17:20.646178896Z" level=fatal msg="Error starting daemon: error initializing graphdriver: driver not supported".Output of
docker version:Output of
docker info:Additional environment details (AWS, VirtualBox, physical, etc.):
tested in VirtualBox
Steps to reproduce the issue:
--storage-driver=overlay2Describe the results you received:
docker daemon start failure due to initialization check for kernel version >= 4.0 when running docker with overlay2 storage driver on EL 7.2
Describe the results you expected:
success running docker with overlay2 storage driver on EL 7.2