On Tue, 2025-09-02 at 23:34 +0200, Tobias Waldekranz wrote: > On tis, sep 02, 2025 at 16:46, Jan Lübbe <[email protected]> wrote: > > On Tue, 2025-09-02 at 11:03 +0200, Ahmad Fatoum wrote: > > > > Yeah I noticed that, _very_ useful. For Infix, if we end up going with > > > > LVM, I suspect we won't be able to send all of that info along with the > > > > commandline, and will end up needing to figure that out (again) in an > > > > initramfs - but for most cases I think it would work really well! > > > > > > Ah, didn't think of LVM. If mix-and-match is no problem for you, then > > > doing it in the initramfs is a workable solution of course. > > > > If you are thinking about LVM, you may want to take a look at how Android is > > using dm-linear for "dynamic partitions": > > https://source.android.com/docs/core/ota/dynamic_partitions/ab_launch > > https://source.android.com/docs/core/ota/dynamic_partitions/implement > > > > This is also related to virtual A/B: > > https://source.android.com/docs/core/ota/virtual_ab > > > > The components are "snapuserd" and "dm-user" (which was not merged): > > https://lpc.events/event/11/contributions/1049/attachments/826/1562/2021%20LPC_%20dm-snapshot%20in%20user%20space.pdf > > https://lwn.net/Articles/838986/ > > > > I'm not sure what they use at the moment... > > Very interesting, thank you! > > I get why they want something like that for Android, but it does feel > quite daunting to deploy for the systems I typically work on. > > If one was to ignore the business of background-merging of COW data > etc. and was just looking to have a way of allocating volumes from > persistent storage, do you see any advantages with Android's metadata > format and/or tooling over that provided by the LVM2 project?
LVM2 in general is quite complex. Some people don't like that it's not easily possible to know (in udev/systemd) when all volumes are found and set-up, making boot time dependencies difficult. The Android metadata (or something similar) seems to be simple enough to implement in a bootloader. So, as we only need a small subset of the full LVM functionality on embedded devices, perhaps there's space for a lightweight alternative? :) Jan -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
