Need to Extend Data Partition After Resizing RootFS

[schorsche32]

Hey there,

I need a modification to the resizing script for my application. Specifically, I want the data partition (p2) to occupy the unallocated space after:

• The first rootfs partition (p3) is extended to approximately twice its original size.
• A second rootfs partition (p4) is created with the same size as p3
  Here is the initial layout:

+------------+----------+--------+---------------------+
| p1         | p2       | p3     |  (unallocated)|
+------------+----------+--------+---------------------+
^ Boot       ^ /data    ^ RootFS

And here is the desired layout:

+-------------+-----------------------+---------------+--------+
| p1          | p2 (extended)         | p3            | p4     |
+-------------+-----------------------+---------------+--------+
^ Boot        ^ /data                 ^ RootFS_A      ^ RootFS_B

My initial idea was to create a fifth primary partition, but that isn’t possible due to the partition limit. Directly extending p2 also appears non-trivial, since it currently overlaps with p3.

Does anyone have a suggestion for how to solve this?

Thank you in advance for any help!

Best regards,
Georg

[lueschem]

I actually like your idea with the fifth partition. AFAIK the Raspberry Pi bootloader does support an MBR/GPT hybrid partition table setup. With a GPT partition table you can go beyond 4 partitions. The Home Assistant community also shared some obstacles they encountered with the GPT setup (along with how they removed those obstacles).

Another possibility would be to boot into an initial ramdisk and do the partition resizing and moving from there. However, I personally prefer your approach of using 5 partitions.

[schorsche32]

I have now developed a new approach.

Initial layout:

+------------+--------+---------------------+
| p1         | p2    |  (unallocated)|
+------------+--------+---------------------+
^ Boot       ^ RootFS

Final layout:

+-------------+------------------+---------------+--------------+
| p1          | p2               | p3            |p4 (extended)
+-------------+------------------+---------------+--------------+
^ Boot         ^ RootFS_A        ^ RootFS_B      ^ /data               

To implement this approach, I need to:

• Create the p4 partition during the first boot.
• Copy the files from rootfs/data to the p4 partition.
• Mount the p4 partition to /data.
• During A/B updates, remove the contents of the newly downloaded rootfs in the /data folder.

Currently, this approach appears to be working well.

I will share it soon in a fork.