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

[Baruch Siach <baruch@tkos.co.il>]

Hi Slava,

On Thu, Feb 08 2024, Vyacheslav Yurkov wrote:
> On 08.02.2024 08:22, Baruch Siach wrote:
>> Don't remount rootfs read-write when read-only-rootfs feature is
>> enabled. Assume that all mount points are in place for the read-only
>> case.
>>
>> Cc: Vyacheslav Yurkov <uvv.mail@gmail.com>
>> Signed-off-by: Baruch Siach <baruch@tkos.co.il>
>> ---
>>   meta/classes-recipe/overlayfs-etc.bbclass |  4 +++-
>>   meta/files/overlayfs-etc-preinit.sh.in    | 16 +++++++++-------
>>   2 files changed, 12 insertions(+), 8 deletions(-)
>>
>> diff --git a/meta/classes-recipe/overlayfs-etc.bbclass b/meta/classes-recipe/overlayfs-etc.bbclass
>> index 0c7834d01f43..e695ebdcf843 100644
>> --- a/meta/classes-recipe/overlayfs-etc.bbclass
>> +++ b/meta/classes-recipe/overlayfs-etc.bbclass
>> @@ -69,7 +69,9 @@ python create_overlayfs_etc_preinit() {
>>           'OVERLAYFS_ETC_FSTYPE': overlayEtcFsType,
>>           'OVERLAYFS_ETC_DEVICE': overlayEtcDevice,
>>           'SBIN_INIT_NAME': initBaseName + origInitNameSuffix if useOrigInit else initBaseName,
>> -        'OVERLAYFS_ETC_EXPOSE_LOWER': "true" if exposeLower else "false"
>> +        'OVERLAYFS_ETC_EXPOSE_LOWER': "true" if exposeLower else "false",
>> +        'READ_ONLY_ROOTFS': bb.utils.contains("IMAGE_FEATURES", "read-only-rootfs",
>> +                                              "true", "false", d)
>>       }
>>         if useOrigInit:
>> diff --git a/meta/files/overlayfs-etc-preinit.sh.in b/meta/files/overlayfs-etc-preinit.sh.in
>> index 8db076f4ba65..79cecf8ac97d 100644
>> --- a/meta/files/overlayfs-etc-preinit.sh.in
>> +++ b/meta/files/overlayfs-etc-preinit.sh.in
>> @@ -3,12 +3,15 @@
>>   echo "PREINIT: Start"
>>     PATH=/sbin:/bin:/usr/sbin:/usr/bin
>> -mount -o remount,rw /
>> -
>> -mkdir -p /proc
>> -mkdir -p /sys
>> -mkdir -p /run
>> -mkdir -p /var/run
>> +if ! {READ_ONLY_ROOTFS}; then
>> +    mount -o remount,rw /
>> +
>> +    mkdir -p /proc
>> +    mkdir -p /sys
>> +    mkdir -p /run
>> +    mkdir -p /var/run
>> +    mkdir -p {OVERLAYFS_ETC_MOUNT_POINT}
>> +fi
>
> I don't think this would be a correct approach. You probably should only
> remount to ro after all mount points are created.

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?

> 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 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?

Thanks,
baruch

>
>>   mount -t proc proc /proc
>>   mount -t sysfs sysfs /sys
>> @@ -20,7 +23,6 @@ UPPER_DIR=$BASE_OVERLAY_ETC_DIR/upper
>>   WORK_DIR=$BASE_OVERLAY_ETC_DIR/work
>>   LOWER_DIR=$BASE_OVERLAY_ETC_DIR/lower
>>   -mkdir -p {OVERLAYFS_ETC_MOUNT_POINT}
>>   if mount -n -t {OVERLAYFS_ETC_FSTYPE} \
>>       -o {OVERLAYFS_ETC_MOUNT_OPTIONS} \
>>       {OVERLAYFS_ETC_DEVICE} {OVERLAYFS_ETC_MOUNT_POINT}
>
> Thanks,
> Slava


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