[Bug 1666573] Re: transient systemd ordering cycle in boot with overlayroot ver read-only open-iscsi root

[Dimitri John Ledkov]

Also see http://unix.stackexchange.com/questions/296148/how-to-remount-a
-systemd-mount-unit-with-different-options

I do not know how one can resolve the '/' mount which hosts '/media
/root-ro', with remount of '/media/root-ro' as '/'. As both mounts are
'-.mount' in the systemd brain.

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Title:
  transient systemd ordering cycle in boot with overlayroot ver read-
  only open-iscsi root

Status in open-iscsi package in Ubuntu:
  Confirmed

Bug description:
  In the open-iscsi test we boot a read-only root iscsi target, using
  overlayroot.

  Transiently this operation fails, ultimately leading to emergency shell.
  Since this occurs in automated test, there is no access to that console
  (it is being logged to a file).

  The open iscsi test that triggers this is described at [1], including how
  to run it.

  Most recently, the open-iscsi version 2.0.873+git0.3b4b4500-14ubuntu17 has
  run both successfully and failed when running for trigger cloud-utils and
  systemd [2]

  I am attaching a tarball with logs and artifacts from the autopackage
  test runs here for posterity.

  In the failure case we see evidence of failure at
    [   52.729092] systemd[1]: media-root\x2dro.mount: Found ordering cycle on media-root\x2dro.mount/start
    [   52.730938] systemd[1]: media-root\x2dro.mount: Found dependency on -.mount/start
    [   52.735138] systemd[1]: media-root\x2dro.mount: Found dependency on media-root\x2dro.mount/start
    [   52.739910] systemd[1]: Unable to break cycle
    [   52.744992] systemd[1]: Requested transaction contains an unfixable cyclic ordering dependency: Resource deadlock avoided

  And then it all goes sour later with:
    [ TIME ] Timed out waiting for device dev-disk-by\x2dlabel-UEFI.device.
    [DEPEND] Dependency failed for /boot/efi.
    [DEPEND] Dependency failed for Local File Systems.
    [ TIME ] Timed out waiting for device VIRTUAL-DISK cloudimg-rootfs.

  
  for reference, the image's fstab is:
    LABEL=cloudimg-rootfs   /        ext4   defaults        0 0
    LABEL=UEFI      /boot/efi       vfat    defaults        0 0

  but /etc/fstab is updated by overlayroot in the initramfs, and as such 
  contains the following:
    #
    #  This fstab is in an overlay. The real one can be found at
    #  /media/root-ro/etc/fstab
    #  The original entry for '/' and other mounts have been updated to be placed
    #  under /media/root-ro.
    #  To permanently modify this (or any other file), you should change-root into
    #  a writable view of the underlying filesystem using:
    #      sudo overlayroot-chroot
    #
    LABEL=cloudimg-rootfs /media/root-ro/ ext4 ro,defaults 0 0
    /media/root-ro/ / overlay lowerdir=/media/root-ro/,upperdir=/media/root-rw/overlay/,workdir=/media/root-rw/overlay-workdir/_ 0 0
    LABEL=UEFI /boot/efi vfat defaults 0 0 # overlayroot:fs-unsupported

  --
  [1] https://git.launchpad.net/~usd-import-team/ubuntu/+source/open-iscsi/tree/debian/tests/README-boot-test.md?h=ubuntu/devel
  [2] http://autopkgtest.ubuntu.com/packages/o/open-iscsi/zesty/amd64

  ProblemType: Bug
  DistroRelease: Ubuntu 17.04
  Package: open-iscsi 2.0.873+git0.3b4b4500-14ubuntu17
  ProcVersionSignature: User Name 4.9.0-15.16-generic 4.9.5
  Uname: Linux 4.9.0-15-generic x86_64
  ApportVersion: 2.20.4-0ubuntu2
  Architecture: amd64
  Date: Tue Feb 21 15:50:58 2017
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: open-iscsi
  UpgradeStatus: No upgrade log present (probably fresh install)
  modified.conffile..etc.iscsi.iscsid.conf: [inaccessible: [Errno 13] Permission denied: '/etc/iscsi/iscsid.conf']

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