From 81ad9419e35af871a62242db09e4330a3314407c Mon Sep 17 00:00:00 2001 From: Andrew Jeddeloh Date: Fri, 17 Aug 2018 10:33:21 -0700 Subject: [PATCH] design doc: add design doc Add a document to record conclusions from dicsussions in the issues section. --- Design.md | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 Design.md diff --git a/Design.md b/Design.md new file mode 100644 index 0000000..63dbc4f --- /dev/null +++ b/Design.md @@ -0,0 +1,41 @@ +# Design Document + +This document captures the design decisions made after discussion in issues. When a design issue is closed, the +conclusion should be summarized here with a link to the issue. + +## Disk Layout + +Originally discussed in issue [#18](https://github.com/coreos/fedora-coreos-tracker/issues/18). See also [dustymabe's comment](https://github.com/coreos/fedora-coreos-tracker/issues/18#issuecomment-409668929) summarizing the discussion in the FCOS meeting. + +### Summary: + + - FCOS will use a "dd-able" image and ship with a standard partition layout. + - The bare metal image and cloud images have the same layout. + - Anaconda will not be used for installation. + - FCOS should not use the [GPT generator](https://www.freedesktop.org/software/systemd/man/systemd-gpt-auto-generator.html). + - LVM should be supported, but not used by default. + - Ignition will be used to customize disk layouts. + +FCOS should have a fixed partition layout that Ignition can modify on first boot. The installer will be similar to the +Container Linux installer; the core of it will be dd'ing an image to the disk. + +The partition layout is still undecided, but initial proposals look something like: + + Number Type Purpose + ----------------------------------- + 1 fat32 Boot partition/ESP + 2 N/A Bios Boot partition + 3 ? Root + 4 ? /var + +We also want to support moving the root partition to new locations by recreating the OSTree at the new location. This +would involve downloading the OSTree repo contents and doing the deploy between the Ignition disks and files stage if +the root filesystem has changed. This is currently untested. + +### Open Questions: + + - What do we do about 4k sector disks? We could make a "hybrid" disk image, but it technically breaks the GPT spec and + may not work with poorly implemented UEFIs. + - What is the exact partition layout? + - Do we make /etc a ro bind mount? + - What filesystem do we use for / and /var? ext4?