hack/install.sh should encourage installation of linux-image-generic on Ubuntu

[z0u]

I installed Docker on Ubuntu 14.04 under OpenStack using the standard install script, built some images and then started some containers. Then I ran a dist-upgrade on the host, which installed a new kernel version, and rebooted. When the machine came back up, all my containers and images were missing.

I think this is because the aufs kernel module was missing from the new kernel. I don't know for sure, because in the process of debugging this I deleted the stuff in /var/lib/docker. Oops :)

I think the reason this happened is:

• The installation script installs the linux-image-extra... package specific to the currently-running kernel.
• The OpenStack Ubuntu image doesn't come with linux-image-generic installed; it has linux-image-virtual, which does not depend on the -extra package.
• When I ran the upgrade, the kernel was upgraded but the -extra package was not, meaning the aufs driver went missing.

Perhaps the install script should show a warning if the linux-image-generic package is not installed?

docker version:

Client version: 1.5.0
Client API version: 1.17
Go version (client): go1.4.1
Git commit (client): a8a31ef
OS/Arch (client): linux/amd64
Server version: 1.5.0
Server API version: 1.17
Go version (server): go1.4.1
Git commit (server): a8a31ef

docker info:

Containers: 0
Images: 29
Storage Driver: aufs
 Root Dir: /var/lib/docker/aufs
 Backing Filesystem: extfs
 Dirs: 29
Execution Driver: native-0.2
Kernel Version: 3.13.0-49-generic
Operating System: Ubuntu 14.04.2 LTS
CPUs: 4
Total Memory: 7.798 GiB
Name: foo
ID: bar
WARNING: No swap limit support

uname -a:

Linux foo 3.13.0-49-generic #83-Ubuntu SMP Fri Apr 10 20:11:33 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

[thaJeztah]

Thanks for reporting this, @z0u. We recently made some improvements in this area (see #11999). Docker will now scan which driver(s) was/were previously used and produce an error if that driver is no longer supported on your system.

I think that change didn't make it in docker 1.6, but will be in docker 1.7.

/cc @vbatts @tianon

[tianon]

I believe #10860 is definitely relevant here. 👍

[z0u]

Thanks @thaJeztah, that sounds like a good solution.

Thanks @tianon. FWIW, installing linux-image-generic didn't change the kernel that was installed on my OpenStack instance.

[cpuguy83]

Closing since #10860 was merged which contains the warning.