<div dir="auto">Whoops, forgot to reply-all and replied directly to Lennart. Forwarding to the ML</div><div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">---------- Forwarded message --------- From: Adrian Vovk <<a href="mailto:adrianvovk@gmail.com">adrianvovk@gmail.com</a>> Date: Thu, Mar 2, 2023 at 16:59 Subject: Re: [systemd-devel] Immutable Images: Single Data Patition To: Lennart Poettering <<a href="mailto:lennart@poettering.net">lennart@poettering.net</a>> </div> > /home/ with dm-integrity or OPAL for trust, TPM-bound, with homed managed homedirs inside that do encryption How big is the dm-integrity write performance hit? My understanding is that it is 2x slower, though I don't recall where I got this info. Maybe it'd be more beneficial to push through authenticated BTRFS into the kernel and only support BTRFS on the unencrypted home partition? This replaces btrfs's hashes with crypto hashes keyed on whatever, which allows us to do the equivalent of dm-integrity but w/o the performance hit (in theory) > With that you'd have to figure out three sizes, i.e. how to size 2/3, how to size 4 and how to size 5. Yes we're on the same page here > And suddenly we'd have a spec that would be particularly powerful and generic: you could use it for subvols, for dirs, or for loopback files, and mix and match freely, and it would always behave somewhat the same way Makes sense. Is there someone I can collaborate with and/or somewhere to go to talk about this and maybe get that TODO resolved & implemented? > dm-linear Would we be able to reclaim the data if the partition shrinks? For instance, if the user changes jobs and no longer needs containers, so they delete many gb of containers out of /var. Will we be able to shrink the rootfs partition and then merge chunks back into the extension partition (or make a separate extension partition if the disk is already fragmented?) How would we manage the size of the filesystem? Overcommit it to the size of the extension partition, but keep it minimal on disk? Have adjustable headroom? Will we expect the user to adjust the headroom? > Interesting that ChromeOS and Android came to different solutions there Indeed Best, Adrian </div></div>-- <div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature">Sent from Gmail Mobile</div>