Add error when running overlay over btrfs.

[jessfraz]

Fixes #9820.

[jessfraz]

Ah shit sorry the broken commit pushed, at the airport will update soon

[thaJeztah]

Thanks for picking this up so quickly!

[jessfraz]

np, it was an easy update, ok pushed :)

[jessfraz]

i dont know who has the env to test this other than @LK4D4

[jessfraz]

@bobrik if you want to test too that would be cool, no worries if not ;)

[bobrik]

@jfrazelle I can check if I get an error if you tell me where to get the build.

[jessfraz]

I will make some binaries and push to s3

[jessfraz]

Here you go thanks!
http://jesss.s3.amazonaws.com/docker/pr9834/linux/amd64/docker-1.4.1-dev
http://jesss.s3.amazonaws.com/docker/pr9834/linux/amd64/docker-1.4.1-dev.md5
http://jesss.s3.amazonaws.com/docker/pr9834/linux/amd64/docker-1.4.1-dev.sha256

[bobrik]

I've got a little paranoid and decided to compile binary myself. Guess what?

~ λ curl https://docs.docker.com/
curl: (60) SSL certificate problem: Invalid certificate chain
More details here: http://curl.haxx.se/docs/sslcerts.html

curl performs SSL certificate verification by default, using a "bundle"
 of Certificate Authority (CA) public keys (CA certs). If the default
 bundle file isn't adequate, you can specify an alternate file
 using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
 the bundle, the certificate verification probably failed due to a
 problem with the certificate (it might be expired, or the name might
 not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
 the -k (or --insecure) option.

[jessfraz]

whoa thats weird... maybe a SNI problem? and I swear I wouldnt give you a virus lol, unless it was an adobe flash plugin

[bobrik]

Okay, I compiled docker myself, it fails to start as expected:

ERRO[0000] 'overlay' is not supported over btrfs filesystems. Please use over ext4.
FATA[0000] backing file system is unsupported for this graph driver

Still works fine on ext4. LGTM then.

Forget about SSL issue, looks like an issue on my side.

[jessfraz]

yayyy thanks!

[LK4D4]

This is little confusing :) Message is about using over ext4, but you checking for btrfs. Maybe I am using reiser.
Should we deny to run overlay over any fs which is not ext4?

[xiaods]

@SvenDowideit mentioned below request:
can we also add the underlying FS to docker info? (for all graph drivers that have them..)

it also need consider.

[jessfraz]

@xiaods I think that can be a separate pr

[jessfraz]

@LK4D4 I will update

[jessfraz]

updated!

[jessfraz]

I got the magic number for ext4 from http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/include/linux/magic.h

[LK4D4]

LGTM

[icecrime]

Review session with @tiborvass @crosbymichael @unclejack

@LK4D4 We're actually disagreeing with your previous comment: we'd rather have a blacklist of unsupported fs (btrfs + aufs for the moment) than a whitelist of supported fs (especially as ext4 shouldn't be the only one). What about things such as xfs?

[crosbymichael]

Overlayfs is supported with XFS

[jessfraz]

ah ok cool so should I just blacklist Aufs and btrfs what about reiser

[jessfraz]

ok I updated, I put two seperate errors, but I would combine into one if, but I was just trying to avoid someone opening an issue about how we don't tell them what they are running and the error is "vague"

[crosbymichael]

LGTM