Re: [PATCH v2] overlayfs-etc: add option to skip creation of mount dirs

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

Hi Slava,

On Mon, Feb 12 2024, Vyacheslav Yurkov wrote:
> On 12.02.2024 19:30, Baruch Siach wrote:
>> The 'preinit' script can't create mount directories when rootfs is
>> read-only. Add an option to skip this step. The user must make sure that
>> all required directories are already in the rootfs directory layout.
>>
>> Cc: Vyacheslav Yurkov <uvv.mail@gmail.com>
>> Signed-off-by: Baruch Siach <baruch@tkos.co.il>
>> ---
>> v2: Add a user selectable option. Don't skip mkdir automatically when
>>      read-only-rootfs feature is enabled.
>> ---
>>   meta/classes-recipe/overlayfs-etc.bbclass |  5 ++++-
>>   meta/files/overlayfs-etc-preinit.sh.in    | 16 +++++++++-------
>>   2 files changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/meta/classes-recipe/overlayfs-etc.bbclass b/meta/classes-recipe/overlayfs-etc.bbclass
>> index 0c7834d01f43..d339fbbeee9f 100644
>> --- a/meta/classes-recipe/overlayfs-etc.bbclass
>> +++ b/meta/classes-recipe/overlayfs-etc.bbclass
>> @@ -41,6 +41,7 @@ OVERLAYFS_ETC_USE_ORIG_INIT_NAME ??= "1"
>>   OVERLAYFS_ETC_MOUNT_OPTIONS ??= "defaults"
>>   OVERLAYFS_ETC_INIT_TEMPLATE ??= "${COREBASE}/meta/files/overlayfs-etc-preinit.sh.in"
>>   OVERLAYFS_ETC_EXPOSE_LOWER ??= "0"
>> +OVERLAYFS_ETC_CREATE_MOUNT_DIRS ??= "1"
>>     python create_overlayfs_etc_preinit() {
>>       overlayEtcMountPoint = d.getVar("OVERLAYFS_ETC_MOUNT_POINT")
>> @@ -62,6 +63,7 @@ python create_overlayfs_etc_preinit() {
>>       initBaseName = oe.path.join(d.getVar("base_sbindir"), "init")
>>       origInitNameSuffix = ".orig"
>>       exposeLower = oe.types.boolean(d.getVar('OVERLAYFS_ETC_EXPOSE_LOWER'))
>> +    createMoundDirs = oe.types.boolean(d.getVar('OVERLAYFS_ETC_CREATE_MOUNT_DIRS'))
>>         args = {
>>           'OVERLAYFS_ETC_MOUNT_POINT': overlayEtcMountPoint,
>> @@ -69,7 +71,8 @@ python create_overlayfs_etc_preinit() {
>>           'OVERLAYFS_ETC_FSTYPE': overlayEtcFsType,
>>           'OVERLAYFS_ETC_DEVICE': overlayEtcDevice,
>>           'SBIN_INIT_NAME': initBaseName + origInitNameSuffix if useOrigInit else initBaseName,
>> -        'OVERLAYFS_ETC_EXPOSE_LOWER': "true" if exposeLower else "false"
>> +        'OVERLAYFS_ETC_EXPOSE_LOWER': "true" if exposeLower else "false",
>> +        'CREATE_MOUNT_DIRS': "true" if createMoundDirs else "false"
>>       }
>>         if useOrigInit:
>> diff --git a/meta/files/overlayfs-etc-preinit.sh.in b/meta/files/overlayfs-etc-preinit.sh.in
>> index 8db076f4ba65..b05e3957a382 100644
>> --- a/meta/files/overlayfs-etc-preinit.sh.in
>> +++ b/meta/files/overlayfs-etc-preinit.sh.in
>> @@ -3,12 +3,15 @@
>>   echo "PREINIT: Start"
>>     PATH=/sbin:/bin:/usr/sbin:/usr/bin
>> -mount -o remount,rw /
>> -
>> -mkdir -p /proc
>> -mkdir -p /sys
>> -mkdir -p /run
>> -mkdir -p /var/run
>> +if {CREATE_MOUNT_DIRS}; then
>> +    mount -o remount,rw /
>> +
>> +    mkdir -p /proc
>> +    mkdir -p /sys
>> +    mkdir -p /run
>> +    mkdir -p /var/run
>> +    mkdir -p {OVERLAYFS_ETC_MOUNT_POINT}
>> +fi
>>     mount -t proc proc /proc
>>   mount -t sysfs sysfs /sys
>> @@ -20,7 +23,6 @@ UPPER_DIR=$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}
>
> Hi Baruch,
> Thanks for the v2. Looks good now. Could you please also add a test case to
> cover the new option?
>
> You saw from the test that mount output is parsed to confirm whether overlay
> is actually mounted. sda3 is a 3rd partition from
> https://git.openembedded.org/openembedded-core/tree/meta-selftest/wic/overlayfs_etc.wks.in
> . We could change rootfs (2nd partition) in the file to substitute the fs type
> (ext4/squashfs) from the test and then check that everything is mounted
> correctly. Does it make sense?

Makes sense.

I added mkdirhier of OVERLAYFS_ETC_MOUNT_POINT for the case of
OVERLAYFS_ETC_CREATE_MOUNT_DIRS == 0. Let me know if there is a better
solution for read-only filesystems.

The trouble with testing is that I could not find any existing feature
in yocto-kernel-cache that enables either CONFIG_SQUASHFS or
CONFIG_EROFS_FS. Is there another way to enable kernel features for the
test?

Thanks,
baruch

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