Two questions:
Why devices (octeon/ubnt_edgerouter, x86-64/generic pcengines apu) with mmcblk use ofsetted root overlay loop mount instead of a separate parition?
Is there another way to use a separate partition for overlay other than pass FILES=dir to imagebuilder with a dir/etc/config/fstab file with a section like this?
config mount
option label 'rootfs_data'
option target '/overlay'
option enabled '1'
option enabled_fsck '1'
counter question, are you sure it applies to ext4 too ?
Not sure if I understand it correctly: ext4 instead of squashfs?
For octeon ubnt_edgerouter imagebuilder produces only squashfs image. I tried to build it manually:
% cat config.diff
--- openwrt-imagebuilder-21.02.3-octeon.Linux-x86_64/.config 2022-04-16 15:59:34.000000000 +0300
+++ ../openwrt-imagebuilder-21.02.3-octeon.Linux-x86_64/.config 2022-05-20 14:50:48.156999340 +0300
@@ -170,10 +170,21 @@
# CONFIG_TARGET_ROOTFS_CPIOGZ is not set
# CONFIG_TARGET_ROOTFS_TARGZ is not set
+CONFIG_TARGET_KERNEL_PARTSIZE=16
+CONFIG_TARGET_ROOTFS_PARTSIZE=256
+CONFIG_TARGET_ROOTFS_PARTNAME=""
+
#
# Root filesystem images
#
# CONFIG_TARGET_ROOTFS_EXT4FS is not set
+CONFIG_TARGET_ROOTFS_EXT4FS=y
+CONFIG_TARGET_EXT4_RESERVED_PCT=0
+CONFIG_TARGET_EXT4_BLOCKSIZE_4K=y
+# CONFIG_TARGET_EXT4_BLOCKSIZE_2K is not set
+# CONFIG_TARGET_EXT4_BLOCKSIZE_1K is not set
+CONFIG_TARGET_EXT4_BLOCKSIZE=4096
+# CONFIG_TARGET_EXT4_JOURNAL is not set
CONFIG_TARGET_ROOTFS_SQUASHFS=y
CONFIG_TARGET_SQUASHFS_BLOCK_SIZE=256
CONFIG_TARGET_UBIFS_FREE_SPACE_FIXUP=y
But sysupgrade fails:
root@OpenWrt:~# sysupgrade -n -v /tmp/openwrt-21.02.3-octeon-ubnt_edgerouter-ext
4-sysupgrade.tar
Tue Jun 21 06:00:02 UTC 2022 upgrade: Image metadata not present
Tue Jun 21 06:00:14 UTC 2022 upgrade: Commencing upgrade. Closing all shell sessions.
*** NMI Watchdog interrupt on Core 0x00 ***
$0 0x0000000000000000 at 0xffffffff81a50000
v0 0xffffffff81a50000 v1 0x0000000000245844
a0 0x0000000000245842 a1 0xffffffff818c4700
a2 0x0000000010009ce0 a3 0xffffffffffff00fe
a4 0xffffffff818c0000 a5 0x0000000000000001
a6 0x0000000000000000 a7 0x0000000000000000
t0 0x0000000000000000 t1 0x0000000000009c00
t2 0x0000000000ffff00 t3 0x0000000000000000
s0 0xffffffff818bf320 s1 0x0000000000000001
s2 0xffffffff818c0000 s3 0xffffffff817aaa38
s4 0xffffffff818d0000 s5 0x0000000000000001
s6 0x8000000002b0ac00 s7 0xffffffff81795120
t8 0x0000000000000000 t9 0xffffffff8179a920
k0 0x0000000000000000 k1 0x0000000000000001
gp 0xffffffff818a8000 sp 0xffffffff818abd90
s8 0x0000000001100000 ra 0xffffffff81162df0
err_epc 0xffffffff811176e0 epc 0xffffffff811176e0
status 0x0000000010489ce5 cause 0x0000000000800000
sum0 0x0080000000000000 en0 0x09a0200500008000
*** Chip soft reset soon ***
*** NMI Watchdog interrupt on Core 0x01 ***
$0 0x0000000000000000 at 0x0000000000000001
v0 0x000000fff335e347 v1 0x000000fff335b1c8
a0 0x000000fff335b1c8 a1 0x000000fff335e570
a2 0x0000000000000400 a3 0x0000000000000000
a4 0x000000fff32c8858 a5 0x0000000000000000
a6 0x0000000000000000 a7 0x0000000000000000
t0 0x0000000000000000 t1 0x800000008b29fd58
t2 0xffffffff81279120 t3 0x0000000000800001
s0 0x000000fffbb19cf8 s1 0x0000000000000003
s2 0x0000000000000000 s3 0x0000000000000008
s4 0x0000000000000001 s5 0x000000012007a37e
s6 0x000000fff335b1c8 s7 0x0000000120076e30
t8 0x0000000000000cc8 t9 0x000000fff331eecc
k0 0x000000000004e798 k1 0xffffffff81a50008
gp 0x000000012009d020 sp 0x000000fffbb19b70
s8 0x0000000000000001 ra 0x0000000120021cb4
err_epc 0x000000fff331eed4 epc 0x000000fff331bd80
status 0x0000000000489cf5 cause 0x0000000000800020
sum0 0x0080000000000000 en0 0x0000000100000000
*** Chip soft reset soon ***
Jumping to start of image at address 0xbfca0000
Anyway all this doesn't answer the main question: why not to use a separate partition for overlay out of the box?