Re: [PATCH v2] expand-on-first-boot: Allow expanding extended MBR partitions

[Jan Kiszka <jan.kiszka@siemens.com>]

On 15.06.20 12:27, [ext] Jan Kiszka wrote:
> On 15.06.20 12:10, Harald Seiler wrote:
>> Extended partitions cannot be resized like primary partitions because
>> both the last logical partition and the EBR primary partition containing
>> it need to be expanded.
>>
>> To do this, add a second SED directive for removing the parition size of
>> the EBR partition.  This part is detected by having either type `f` (Win
>> 95 Ext') or `5` (Extended).
>>
>> Signed-off-by: Harald Seiler <hws@denx.de>
>> ---
>>
>> Notes:
>>     Changes in v2:
>>     - Keep a type `f` EBR as type `f`.
>>     - Update comment to better explain what is done.
>>     
>>     I've built myself a little test-suite to see how this script
>>     behaves when given different layouts.  It seems to work just fine
>>     now for the following cases:
>>     
>>     - Expanding last partition of a GPT.
>>     - Expanding last partition of an MBR without extended partitions.
>>     - Expanding last (logical) partition of an MBR when the last
>>       primary partition is the EBR.
>>     
>>     Having the EBR somewhere in the middle is *not* supported.  The
>>     script will fail with an error message, without accidentally
>>     ruining the layout.  I think such a case is too rare to be worth
>>     supporting.
> 
> Ack.
> 
>>
>>  .../files/expand-last-partition.sh             | 18 +++++++++++++-----
>>  1 file changed, 13 insertions(+), 5 deletions(-)
>>
>> diff --git a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
>> index 08c69db30529..7175dfd38b7e 100755
>> --- a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
>> +++ b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
>> @@ -17,12 +17,20 @@ if [ "${ROOT_DEV}" = "${BOOT_DEV}" ]; then
>>  	exit 1
>>  fi
>>  
>> -LAST_PART="$(sfdisk -d ${BOOT_DEV} 2>/dev/null | tail -1 | cut -d ' ' -f 1)"
>> +LAST_PART="$(sfdisk -d "${BOOT_DEV}" 2>/dev/null | tail -1 | cut -d ' ' -f 1)"
>>  
>> -# Remove all hints to the current medium (last-lba) and last partition size,
>> -# then ask sfdisk to recreate the partitioning
>> -sfdisk -d "${BOOT_DEV}" 2>/dev/null | grep -v last-lba | \
>> -	sed 's|\('"${LAST_PART}"' .*, \)size=[^,]*, |\1|' | \
>> +# Transform the partition table as follows:
>> +#
>> +# - Remove any 'last-lba' header so sfdisk uses the entire available space.
>> +# - If this partition table is MBR and an extended partition container (EBR)
>> +#   exists, we assume this needs to be expanded as well; remove its size
>> +#   field so sfdisk expands it.
>> +# - For the previously fetched last partition, also remove the size field so
>> +#   sfdisk expands it.
> 
> Very nice.
> 
>> +sfdisk -d "${BOOT_DEV}" 2>/dev/null | \
>> +	grep -v last-lba | \
>> +	sed 's|^\(.*, \)size=[^,]*, \(type=[f5]\)$|\1\2|' | \
>> +	sed 's|^\('"${LAST_PART}"' .*, \)size=[^,]*, |\1|' | \
>>  	sfdisk --force "${BOOT_DEV}"
>>  
>>  # Inform the kernel about the partitioning change
>>
> 
> LGTM.
> 
> Jan
> 

Baurzhan, this is overdue.

Jan

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