** Summary changed: - why does booting any livefs squashfs cause the kernel to complain about being unable to read metadata + why does booting any livefs squashfs cause the kernel to complain about being unable to read metadata‽
** Tags added: rls-ff-incoming -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1824407 Title: why does booting any livefs squashfs cause the kernel to complain about being unable to read metadata‽ Status in linux package in Ubuntu: Confirmed Status in linux-hwe package in Ubuntu: Invalid Status in linux-hwe source package in Bionic: Confirmed Bug description: 1) Download focal subiquity daily image 2) boot, and press ESC and edit boot command line (F6 in bios, e in UEFI) 3) Before --- insert the following options bebroken debug init=/bin/bash 4) Continue boot (Enter in BIOS, ctrl+x in UEFI) 5) you will be dropped into pivoted root filesystem, before systemd is execed as pid one 6) /run/initramfs/ will contain a debug log, showing how everything was mounted. Ie. cdrom mounted, squashfs losetup from there, then multilower overlay setup from them, moved to /root, and then pivot-root to /root done to finally end up as /. Underlying layers are moved into /cow for your convenience. 7) At this point modifying zero-byte length files, that exist in the lowest layer, but not the middle one, in certain ways, will results in them to be corrupted, after / is remounted. 8) Exhibit A: $ cat /etc/machine-id (no output) $ systemd-machine-id-setup $ cat /etc/machine-id (some machine id) $ mount -o remount / $ cat /etc/machine-id I/O error with overlay errors in dmesg Similarly one can reproduce this with /etc/.pwd.lock & executing systemd-sysusers. systemd-machine-id-setup is probably the easiest to trace. It does a simply open, truncate, lseek, write. On boot, actuall remount is done by the starting a unit which calls /lib/systemd/systemd-remount-fs Lots of things break once machine-id and .pwd.lock are corrupted. I.e. unable to dhcp, connect to dbus, add/remove/change users or groups, etc. We were unable to recreate the issue outside of booting things with casper. Ie. statically on a regular host machine without pivot-root. But hopefully booting to a quite state with nothing running is sufficient to reproduce this. Instead of booting with `bebroken init=/bin/bash` you can boot with `bebroken systemd.mask=systemd-remount-fs.service` this will complete the boot, with /etc/machine-id & .pwd.lock modified, meaning that remount of / will cause IO errors on those files. Currently, we are shipping two hacks in casper to "rm" the offending files, and create them again on the upper rw layer. They then survive remount without i/o errors. However, we'd rather not ship those hacks, and have kernel overlay fixed to work correctly with multi-lower-dir and not corrupt files upon remounting /. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1824407/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
