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[Martin Pitt <martin.pitt@xxxxxxxxxx>]

> I'm surprised the root filesystem is read-only at the point where
systemd starts. Isn't it remounted rw by the initramfs? (It is in
Debian.)

No, it shouldn't; Usually grub passes the "ro" option in which case
initramfs should leave it as readonly (see /usr/share/initramfs-
tools/init). rw mounting happens in systemd-remount-fs.service.

Sorry for the misunderstanding/false information: Indeed /etc/machine-id
must at least exist (empty is okay) in order to regenerate it -- then
systemd will create a new one in a temporary  location in /run, bind-
mount /etc/machine-id to it, and systemd-machine-id-commit.service will
then write it to /etc/machine-id once the fs becomes read-write. So the
message in the description as well as machine-id(5) ("Optionally, for
stateless systems, it is generated during runtime at boot if it is found
to be empty.") are quite correct.

So this is pretty much "wontfix" on the downstream side. There's
probably a way to combine the above so that writing an entirely absent
/etc/machine-id after the root fs becomes rw, but that should then
happen upstream.

** Changed in: systemd (Ubuntu)
   Importance: Undecided => Low

** Changed in: systemd (Ubuntu)
       Status: New => Won't Fix

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https://bugs.launchpad.net/bugs/1508766

Title:
  /etc/machine-id not created if missing

Status in systemd package in Ubuntu:
  Won't Fix

Bug description:
  If /etc/machine-id is missing at boot, systemd does not create it.

  I came across lp:1387090 in which Martin Pitt mentions that it should
  be created if missing, but is unsure why this doesn't work.

  I'm likewise unsure why it doesn't work, but this bit from dmesg makes
  me think it *might* be because systemd is trying to do so while the
  rootfs is still mounted read-only, before it gets remounted read-
  write:

  [   19.240451] systemd[1]: System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.
  [   19.240464] systemd[1]: Booting up is supported only when:
  [   19.240466] systemd[1]: 1) /etc/machine-id exists and is populated.
  [   19.240467] systemd[1]: 2) /etc/machine-id exists and is empty.
  [   19.240468] systemd[1]: 3) /etc/machine-id is missing and /etc is writable.

  A missing /etc/machine-id file has broad consequences for the boot
  process. As one example, the Journal Service doesn't get started.

  This problem appears to have greater impact now that on Wily (desktop)
  /var/lib/dbus/machine-id is a symlink to /etc/machine-id. Previously
  the system dbus instance would generate the machine-id with dbus-
  uidgen if the file was missing, but on Wily desktop it wont.

  Note that on Wily server /var/lib/dbus/machine-id is a regular file,
  is not a symlink to /etc/machine-id. I filed lp:1508697 about this
  separate issue as it seems strange for this to be different between
  Wily desktop and server.

  Thanks!

  ProblemType: Bug
  DistroRelease: Ubuntu 15.10
  Package: systemd 225-1ubuntu9
  ProcVersionSignature: Ubuntu 4.2.0-16.19-generic 4.2.3
  Uname: Linux 4.2.0-16-generic x86_64
  ApportVersion: 2.19.1-0ubuntu3
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Wed Oct 21 19:57:58 2015
  JournalErrors:
   No journal files were found.
   -- No entries --
  MachineType: System76, Inc. Gazelle Professional
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-16-generic root=UUID=424ed0f3-306d-4302-b58c-6b1e7adb7c74 ro quiet splash vt.handoff=7
  SourcePackage: systemd
  UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 05/16/2012
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 4.6.5
  dmi.board.asset.tag: Tag 12345
  dmi.board.name: Gazelle Professional
  dmi.board.vendor: System76, Inc.
  dmi.board.version: gazp7
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 9
  dmi.chassis.vendor: No Enclosure
  dmi.chassis.version: N/A
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr4.6.5:bd05/16/2012:svnSystem76,Inc.:pnGazelleProfessional:pvrgazp7:rvnSystem76,Inc.:rnGazelleProfessional:rvrgazp7:cvnNoEnclosure:ct9:cvrN/A:
  dmi.product.name: Gazelle Professional
  dmi.product.version: gazp7
  dmi.sys.vendor: System76, Inc.

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