[yocto] rootfs mounted read-only on Live USB (x86-64)

[Bruce Ashfield]

On 2016-06-03 10:15 AM, Dan O'Donovan wrote:
> On 06/03/2016 10:54 AM, Oleksandr Poznyak wrote:
>> Hi,
> Hi Oleksandr
>> Check if "read-only-rootfs" feature is added to any of these variables
>> either in your local.conf or your image bitbake recipe:
>>
>> Something like that:
>>
>> IMAGE_FEATURES = "read-only-rootfs"
>>
>> EXTRA_IMAGE_FEATURES += "read-only-rootfs"
> Thanks for your suggestion.  I didn't find "read-only-rootfs" specified
> in the IMAGE_FEATURES in local.conf or elsewhere.  I suspect it might be
> a different issue because it only affects the live-boot of the .iso
> image.  If I install the .hddimage directly to the storage device
> instead, then it boots fine and the rootfs is read/write.
>
> [update]
> It looks like the problem was indeed the lack of aufs.
> I added this in conf/local.conf
>      DISTRO_FEATURES_append = " aufs"
> and this in the kernel recipe
>      KERNEL_FEATURES_append += "${@bb.utils.contains('DISTRO_FEATURES',
> 'aufs', ' features/aufs/aufs-enable.scc', '', d)}"
> and now the live USB image boots correctly with a read-write filesystem.
>
> Considering that the default images built for a generic x86-64 machine
> include a live-boot image (.iso) which is effectively broken, I assume
> the aufs feature (or another solution for the live-boot use case) should
> really be added by default for those builds as well.

aufs is in the linux-yocto-4.1 and 4.4 kernels. It may be that the
SRCREVs for older branches haven't been updated yet.


commit ed2314d234ff26ed50342264e432392c8908c66b
Author: Bruce Ashfield <bruce.ashfield at windriver.com>
Date:   Wed Jul 8 15:46:25 2015 -0400

     aufs4: core support

     Integrating the core aufs4 support from:

       git://github.com/sfjro/aufs4-standalone.git

     Signed-off-by: Bruce Ashfield <bruce.ashfield at windriver.com>



Bruce

>>
>> Thanks,
>> Oleksandr Poznyak!
>>
>> On Fri, Jun 3, 2016 at 12:06 PM, Dan O'Donovan <dan at emutex.com
>> <mailto:dan at emutex.com>> wrote:
>>
>>     Hi all
>>
>>     Has anyone else noticed that the root file-system appears to be
>>     mounted read-only when booting a Live USB image from Yocto 2.1.
>>
>>     This is on a sato build from the krogoth branch of poky and
>>     meta-intel, for a generic x86-64 machine (4.4 kernel).
>>
>>     I'm transferring the resulting .iso image to a usb stick using
>>     'dd', and then picking the 'boot' option at startup.
>>
>>     As well as a bunch of errors about the read-only filesystem (e.g.
>>     failing to create files in /var and other locations), the desktop
>>     UI fails to load.
>>
>>     This worked fine with Yocto 2.0.
>>
>>     I have a hunch that it might be caused by a lack of aufs support.
>>     Is it possible that aufs patches were omitted from the x86 kernels
>>     in Yocto 2.1?
>>
>>     Thanks,
>>     -Dan
>>
>>     P.S. It works fine if I just install it directly, or if I use the
>>     .hddimg, instead of trying to boot the live image from the .iso.
>>     --
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>>
>>
>
>
>