Partitions on TP-Link WDR4300v1 with OpenWrt 25.12.1

[jock]

I could do with some advice from someone knowledgeable about overlay partitions. It seems weird that /tmp gets a 59M partition, but the overlay root partition gets 640K.

Part of what is confusing me (I'm easily confused) is that I did a factory reset on a second WDR4300. When it came up pristine, I configured it as usual, all working fine. Then on next reboot, it lost all its configuration. I was only able to determine this from failsafe mode -> mount_root

What I think is happening:

• the initial factory reset is fine, and the partitions are mounted correctly (with the relatively ample MBs disk space I would expect in overlay root)
• I'm able to configure the system as expected on a fresh install, writing the config to the mounted partition
• on reboot, the overlay partition with all the custom configuration is not remounted, leaving only the much smaller 640K partition and read-only config - system is bootable, but devoid of meaningful configuration

Is anyone else seeing this, or am I just doing something dumb? I'm not excluding operator error here.

Details of a 'working' WDR4300 below:

root@foo:/# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/root                 4.8M      4.8M         0 100% /rom
tmpfs                    59.0M    256.0K     58.7M   0% /tmp
/dev/mtdblock4          640.0K    252.0K    388.0K  39% /overlay
overlayfs:/overlay      640.0K    252.0K    388.0K  39% /
tmpfs                   512.0K         0    512.0K   0% /dev

root@foo:/tmp# mount
/dev/root on /rom type squashfs (ro,relatime,errors=continue)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
cgroup2 on /sys/fs/cgroup type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
/dev/mtdblock4 on /overlay type jffs2 (rw,noatime)
overlayfs:/overlay on / type overlay (rw,noatime,lowerdir=/,upperdir=/overlay/upper,workdir=/overlay/work)
tmpfs on /dev type tmpfs (rw,nosuid,noexec,noatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,noatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,noatime)
bpffs on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,noatime,mode=700)

Is it that the partition layout in the wiki is out-of-date?

Or is this as intended?

Any advice gratefully received.

[frollic]

/tmp is RAM, not stored on flash.

Over filling /overlay will make device not save and load config properly.

With 8MB flash, 640kb free, posts flash, doesn't sound very unlikely to me.

[jock]

Thank you - so to confirm I've understood: the partition layout looks right to you, and the problem is likely due to me inadvertently filling the 640K overlay partition during initial config?

[frollic]

Config shouldn't fill it that much, additional packages would.

Run a cat /proc/mtdto see the layout of the flash.

[jock]

Thanks - I'll do another factory reset and leave it as vanilla as possible to see if the config survives a reboot this time. I appreciate the help.

[slh]

It's a 8 MB (minus 192 KB for bootloader and ART) flash device, there simply isn't much space left.

[frollic]

It's another device where the 864 warning should be added.

[jock]

I'm back up and running again. Your diagnosis was spot on. Thanks @frollic and @slh