** Also affects: linux-hwe (Ubuntu)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Bionic)
Importance: Undecided
Status: New
** Also affects: linux-hwe (Ubuntu Bionic)
Importance: Undecided
Status: New
** Changed in: linux-hwe (Ubuntu Bionic)
Milestone: None => ubuntu-18.04.4
** Changed in: linux-hwe (Ubuntu Bionic)
Importance: Undecided => Critical
** No longer affects: linux (Ubuntu Bionic)
** Changed in: linux (Ubuntu)
Milestone: None => ubuntu-20.01
** Changed in: linux (Ubuntu)
Importance: Undecided => Critical
** Changed in: linux-hwe (Ubuntu)
Status: New => Invalid
** Changed in: linux (Ubuntu)
Status: New => Confirmed
** Changed in: linux-hwe (Ubuntu Bionic)
Status: New => Confirmed
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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 has kernel complaining about
unable to read metadata something rather
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 /.
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