I’m wondering if that is an over simplified policy? Today turned ugly when I tried to update Discourse. It said I needed to update Docker. I was reminded that I never switched devmapper from loop mode to direct-lvm. According to the Docker site devmapper direct-lvm is the recommended method on Redhat and CentOS. Because AUFS is not supported. Now I have to use --skip-prereqs using the Docker recommended storage driver. Is the default loop mode actually the problem because people never do the xtra steps to direct-lvm (block level)?
> [root@xxxx ~]# docker info
> Containers: 2
> Running: 0
> Paused: 0
> Stopped: 2
> Images: 39
> Server Version: 1.12.6
> Storage Driver: devicemapper
> Pool Name: docker-thinpool
> Pool Blocksize: 524.3 kB
> Base Device Size: 10.74 GB
> Backing Filesystem: xfs
> Data file:
> Metadata file:
> Data Space Used: 490.7 MB
> Data Space Total: 490.7 MB
> Data Space Available: 0 B
> Metadata Space Used: 122.9 kB
> Metadata Space Total: 4.194 MB
> Metadata Space Available: 4.071 MB
> Thin Pool Minimum Free Space: 48.76 MB
> Udev Sync Supported: true
> Deferred Removal Enabled: true
> Deferred Deletion Enabled: true
> Deferred Deleted Device Count: 0
> Library Version: 1.02.135-RHEL7 (2016-11-16)
> Logging Driver: json-file
> Cgroup Driver: systemd
> Plugins:
> Volume: local
> Network: host bridge null overlay
> Swarm: inactive
> Runtimes: docker-runc runc
> Default Runtime: docker-runc
> Security Options: seccomp
> Kernel Version: 3.10.0-514.10.2.el7.x86_64
> Operating System: CentOS Linux 7 (Core)
> OSType: linux
> Architecture: x86_64
> Number of Docker Hooks: 2
> CPUs: 2
> Total Memory: 3.86 GiB
> Name: xxxx
> ID: 4HCD:CXPT:UOD3:TH6S:6CZ3:XOEV:FYIF:GHBZ:OCIR:JBTX:UVG6:G37X
> Docker Root Dir: /var/lib/docker
> Debug Mode (client): false
> Debug Mode (server): false
> Registry: https://index.docker.io/v1/
> Insecure Registries:
> 127.0.0.0/8
> Registries: docker.io (secure)