runtimetest: add root filesystem validation

[Mashimiao]

Signed-off-by: Ma Shimiao [email protected]

[liangchenye]

Hi @Mashimiao I just submitted a PR #81 which does the same thing, but by using mount information.

I think it might be wrong to verify the readonly property of the root file system by using os.stat.
if you mount yourPartition -o /mnt/readonly-point and use os.stat, it might still show us 'drwxr-xr-x. But when you toucha` file in /tmp/readonly-point, it will tell:

touch: cannot touch 'a': Read-only file system

[wking]

On Thu, May 26, 2016 at 03:43:54AM -0700, 梁辰晔 (Liang Chenye) wrote:

if you mount yourPartition -o /mnt/readonly-point and use os.stat,
it might still have write permission. But when you touch a file in
/tmp/readonly-point…

Ah, good point. We should definitely be testing read-only by
attempting writes, because the per-file POSIX-mode permissions are
distinct from the per-mount filesystem options.

[Mashimiao]

@liangchenye @wking re-implemented with pre-write

[wking]

On Thu, May 26, 2016 at 09:47:37PM -0700, Ma Shimiao wrote:

@liangchenye @wking re-implemented with pre-write

I'll leave it to you and @liangchenye to decide whether this rerolled
version takes precedence over #81 ;).

[liangchenye]

@wking Ah! I'll rollback my second commit in #81 :)

[mrunalp]

Probably needs gofmt run.

[Mashimiao]

@mrunalp Ah, sorry. fixed.

[mrunalp]

LGTM