Yesterday I installed openwrt on a rpi4 with the snapshot images. After a few hours I added some further packages. The install procedure failed because of some kernel modules, which required a newer kernel version. I suppose, that the snapshot repository for the rpi4 has been updated during the last hours.
Okay, shit can happen.
To avoid the same situation for the future I would like to know: are there any regular time intervals, where the snapshot repository is updated (e.g. every saturday night)? Or can the update happen at every time (e.g. several times a day)?
snapshots are built daily, and that sets time limits to installing new packages with opkg. Due to kernel version checksums, you can only install “kmod” kernel modules and other kernel version dependent modules from the exactly same snapshot build. So, a few hours after flashing the firmware you may not be able to install new modules with opkg any more
Both images and packages are built roughly once per day for each target, but the frequency depends on the build work needed for the changed packages, as buildbot builds target in a round-robin fashion.
The packages phase2 buildbot uses an SDK built in the firmware images phase1 buildbot, so the packages will be updated to be in line with the new core packages and kernel. Trouble may arise if some "normal" package depends on a package built along the images, and both buildbots have not finished the new matching build rounds.
Ps. there is a similar buildbot for 19.07 and for 18.06.
Either keep a local copy of the repo (or build your own) or update your image to the latest snapshot when you want to install new kernel-dependent packages or kmods. Not the most convenient, but will keep you running.
Because you’re on the RPi4 which is not supported by 19.07, you’ll probably have to wait for an official stable release of the next version(20.x) to be off the snapshot routine. But once on a stable release path, you won’t have to worry about this dance.
In a short sentence: snapshots are a permanently moving target.
In order to get a consistent repository it is best to download the openwrt repository directly after the snapshot creation of the desired target and then working and installing from the local copy.
