Re: [PATCH] overlayfs-etc: take read-only-rootfs into account

[Vyacheslav Yurkov <uvv.mail@gmail.com>]

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On 11.02.2024 14:23, Baruch Siach wrote:
> As I understand, the point of read-only-rootfs feature is to keep rootfs
> intact. Filesystems like squashfs or erofs don't support rw mount at
> all. How can we support this use case?

That's a really good question. I assume we need to differentiate here 
the ro rootfs just because it's set this way in fstab, or ro rootfs, 
which doesn't support writing at all. For the latter you still need all 
your directories already created in the image (squashfs, erofs) or you 
would mount it in some location on tmpfs. Point is, mount point has to 
exist. I suggest we follow the similar approach like in 
overlayfs.bbclass, i.e. we add a flag, which can be used to skip 
directory creation for this use case. Please use 'false' as a default, 
so existing users don't have to change anything when they upgrade their 
Yocto version.

>> With this patch overlayfs.OverlayFSEtcRunTimeTests.test_sbin_init_preinit
>> fails:
>>
>> 2024-02-08 21:12:40,616 - oe-selftest - INFO - Traceback (most recent call
>> last):
>>    File
>> "/home/uvv/projects/upstream/poky/meta/lib/oeqa/core/decorator/__init__.py",
>> line 35, in wrapped_f
>>      return func(*args, **kwargs)
>>    File
>> "/home/uvv/projects/upstream/poky/meta/lib/oeqa/selftest/cases/overlayfs.py",
>> line 370, in test_sbin_init_preinit
>>      self.run_sbin_init(False)
>>    File
>> "/home/uvv/projects/upstream/poky/meta/lib/oeqa/selftest/cases/overlayfs.py",
>> line 399, in run_sbin_init
>>      self.assertTrue("/data" in output, msg=output)
>> AssertionError: False is not true : /dev/sda2 on / type ext4 (ro,relatime)
> Where is this /dev/sda2 coming from? I have also seen it in my
> /etc/fstab once I enabled the overlayfs-etc feature. I see no mention of
> sda2 in meta/lib/oeqa/selftest/cases/overlayfs.py.

The test actually expects sda3 as overlay partition. The partitions are 
created by means of wic, the configuration is in 
https://git.openembedded.org/openembedded-core/tree/meta-selftest/wic/overlayfs_etc.wks.in 
, and pulled in by WKS_FILE in meta/lib/oeqa/selftest/cases/overlayfs.py.

Perhaps we could extend test coverage for your use case by parametrizing 
wks.in file further and placing rootfs on squashfs partition? I haven't 
checked TBH whether wic supports it :)
>> The test is not really explicit, but it looks like overlay is not mounted. We
>> could also add a generic test to search for "PREINIT" done/failed.
> How can I run this test?

Use this command:
oe-selftest -r overlayfs.OverlayFSEtcRunTimeTests.test_sbin_init_preinit

Check also this link https://wiki.yoctoproject.org/wiki/Oe-selftest and 
prepare your environment first


Cheers,
Slava

>
> Thanks,
> baruch

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