/tmp read-only with stretch and FAI 5.1.2

[Stephen Dowdy]

Jeff, (btw, i work with Jeff)
I think it's useful to add some of the other stuff we discovered here.

The overlay fs seems to be setup in 'dracut', and not having ever used
this, i was confused by the parameters for upperdir+workdir
(/cow/{rw,work}) not existing in the running fai environment.
apparently /cow/rw gets bind mounted in dracut to /live/cow, which
does exist in fai environment and reflects changes we make (e.g.
creating character device "blackout/mask" files if we move or delete
stuff in / (which is bind mounted to /live/image)

We have discovered that we can:

    mv /tmp /tmp-
    mkdir /tmp

and after that, BOTH the new /tmp and the old /tmp, now /tmp- are writeable!

This seems to be a bug with the overlayfs (like overlayfs hasn't fully
initialized its namespace or something, and is defaulting to protected
subelements of / by default).   I see people reporting ENOTSUPP when
SELINUX is in play, but it is definitely not in play in the FAI
environment ( no /sys/fs/selinux, nor /selinux )

the "Operation Not Supported" is true for all subdirectories in /,
just not / itself (where you can create, delete, move, etc).  So, this
certainly poses problems in /var as well.

Very strange -- any ideas on known bugs or standard diagnostic
operations for 'overlayfs' appreciated.

thanks,
--stephen



On Wed, Aug 10, 2016 at 9:02 AM, Jeffrey Stolte <stolte at ucar.edu> wrote:
> Thomas,
>
> Thank you for creating the nfsroot tarball.  Unfortunately, using this
> nfsroot produces the same problem for me (/tmp not writeable).  If
> this nfsroot works OK for you, then my problem must be somewhere else.
> Maybe a boot parameter or NFS export option?  I'll keep looking and let
> you know if I find anything.  Thanks.
>
> Jeff



-- 
Stephen Dowdy  -  Systems Administrator  -  NCAR/RAL
303.497.2869   -  sdowdy at ucar.edu        -  http://www.ral.ucar.edu/~sdowdy/