[yocto] Question about wic partition creation

Ed Bartosh ed.bartosh at linux.intel.com
Mon Nov 7 15:13:40 PST 2016

On Tue, Nov 01, 2016 at 11:14:48AM -0400, Nicolas Bigaouette wrote:
> We are using Yocto (jethro and krogoth) to build an image for a device.
> I organized the compilation process into multiple stages for easier
> integration with our tooling. The last stage is a call to `wic` to
> create a drive image that we can then `dd` to a real drive to get a
> workable system.
Do you use wic images produced by bitbake or run wic after bitbake build?

> I am faced with a problem where I would like the top-level directory
> of one of the partition created by wic to have a different owner
> than root.
> I am able to tell wic the partition information (size, filesystem,
> etc.) but I can't find a way to tell wic to change permissions of
> files/directories inside the partition...
> As an example I have an entry like the following at the end of my `.wks`:
> > part /opt/mnt        --label extra  --fstype=ext4 --align 1024
> --ondisk sda --size=2040
> which will add an extra partition after all others on the final
> image. An entry in `/etc/fstab` will be added so that the partition
> will be mounted to `/opt/mnt`.
> Note that the partition should be empty: I'm not populating it with
> any files or directories.
> But after booting the system, the directory `/opt/mnt` will have the
> permissions of the top-level directory of the created partition, and
> by default those are `0755` and owned by `root:root`.
> So my question is: How can I change this so that it's owned by a
> specific uid and gid (`1000:1000`)?

> I am investigating plugins for now (for example by having a
> `meta-mylayer/scripts/lib/wic/plugins/source/fsimage-mypartition.py`)
> but I still can't see how I can change the owner of the directory.
> Should I provide a rootfs-like directory which is empty but owned by
> the proper uid and gid?
Yes, that's what I'd suggest to do. rootfs plugin may help you with
this. If it doesn't work as expected please create bug for me in Yocto

> Note that letting users be able to mount the partition (by adding
> `users` to `/etc/fstab`) is not what I want; it would _not_ change
> the permissions/owner of the top-level directory of the partition.


More information about the yocto mailing list