Following from the Btrfs as rootfs idea in the "Proposal: drop 'Test installation media' from live media" thread, I went down the separate rabbit hole of how to do persistence by default. The following is not Btrfs specific. The xorriso options (isohybrid-mbr, et al) we're using creates a deeply conflicted image. I'm not finding an easy way of dealing with it. The short answer is, I think we need a dedicated image for enabling persistence. Or alternatively, teach Fedora Media Writer how to do substantial surgery akin to livecd-iso-to-disk, but going even further. Here's what I've found with the current Live ISOs used by desktops: 1. The image, and thus the USB stick, is firstly an ISO 9660 image. This format "owns" the entire media, and has no partitions. 2. The image also has MBR and GPT partition maps with different (conflicting) information in them. These are intended to be used by the firmware when booting the image from a USB stick. 3. Because the MBR is not a PMBR, and also has more than one partition entry, per the UEFI spec the GPT is invalid. 4. I haven't discovered a tool that will modify the GPT alone, without insisting on stomping on the MBR. gdisk even refuses to modify the GPT, requiring a completely new GPT. I expect systemd-repart won't touch the GPT either: a) it only supports GPT, b) the GPT is invalid, c) the MBR isn't a PMBR. 5. Overwriting the MBR and GPT with a proper one that contains merged partitions from both the original MBR and GPT still boots both UEFI and BIOS computers. 6. However, following boot, /dev/vda is considered ISO 9660 by linux. None of the partitions will mount. I get EBUSY. 7. I can't create a file system for overlayfs, nor extend the Btrfs seed rootfs, using a spare partition I've created from the vast free space on the USB stick. I get EBUSY. So I'm stuck. The rootfs image needs to be extracted from the ISO 9660 image, in order to bring about the possibility of persistence. Further, it should do so in a way that doesn't require the entire stick to be FAT32 based, which limits root and home to 4G each at best. A. Teach Fedora Media Writer how to do this surgery. B. Teach the compose system, maybe OS Build, to create a ready-to-go image for this purpose. -- Chris Murphy _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
