# Delta update failure / reliability? **URL:** \ **Category:** General Discussions\ **Tags:** raspberry-pi-4, deltaupdate, system-update\ **Created:** [May 17, 2024, 10:54am UTC](https://hub.mender.io/t/delta-update-failure-reliability/6828 "2024-05-17T10:54:06Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![void\_brain](https://avatars.discourse-cdn.com/v4/letter/v/97f17d/32.png) [@void\_brain](https://hub.mender.io/u/void_brain)\ **Post date:** [May 17, 2024, 10:54am UTC](https://hub.mender.io/t/delta-update-failure-reliability/6828/1 "2024-05-17T10:54:06Z")
I am using an rpi4-b, I have tried a lot of delta updates. However sometimes I do have checksums related issues which i do not understand. For instance I have 3 releases: prod-11 prod-12 prod-13 I have already did an incremental update from 11 to 12 to 13. Then later on, when i downgrade to 12 then proceed to an update from prod-12 to prod-11 it does not work with the following error : ```auto 2024-05-17 09:38:31 +0000 UTC info: Running Mender client version: 3.5.1 2024-05-17 09:38:32 +0000 UTC info: State transition: update-fetch [Download_Enter] -> update-store [Download_Enter] 2024-05-17 09:38:32 +0000 UTC info: No public key was provided for authenticating the artifact 2024-05-17 09:38:32 +0000 UTC error: Artifact dependency "rootfs-image.checksum" not satisfied by currently installed artifact (c3168cb3219f91996d0d5edc57a4f8e22d874f225e084c090576d02da1d42330 != f67209e129e4e164291b7c9e72178c6ca5f21556e3b678b0f19683c77a43b427). 2024-05-17 09:38:32 +0000 UTC info: State transition: update-store [Download_Enter] -> update-status-report [none] ``` However when i update once again to prod-13 it works perfectly. How is that possible ? I do have a read only rootfs with an /etc overlay. My rootfs is mounted as ro, I checked` /proc/cmdline` and fstab. I have a symlink from `/usr/share/myapp` to `/data/myapp.` I am afraid that update will fail if my rpi is in the client. So any help would be appreciated.