[Bug 1075313] Re: no reliable way to boot from iscsi root

[Dave Gilbert]

The thing is I'd not necessarily expect the path to be stable; as I said in comment 2, I'd expect the iqn to be
stable, but I wouldn't bet on the IP of the SAN staying stable - it's normal for a SAN to have multiple IPs for multiple controllers
etc, and by the magic of multipath stuff often moves around.

Your line of:

            "ro root=/dev/disk/by-path/ip-%s:%s-iscsi-%s-lun-1" % (
                params.fs_host, "3260", tname

is thus OK if the IP address %s is expanded inside the initramfs at boot
time to see where it's connection is currently coming from, but it's not
safe if that expansion is done when the initramfs is built; and I don't
understand the python or the script your modifying to know which of
those happens.

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https://bugs.launchpad.net/bugs/1075313

Title:
  no reliable way to boot from iscsi root

Status in MAAS:
  Fix Committed
Status in MAAS 1.2 series:
  Fix Committed
Status in “open-iscsi” package in Ubuntu:
  Triaged

Bug description:
  In order to boot from iscsi root via kernel parameters, the user would provide kernel parameters something like:
     iscsi_target_name=some-iscsi-target-name iscsi_target_port=3260 iscsi_target_ip=some.host root=LABEL=SOME_LABEL

  or potentially the same above but with root=UUID=SOME_UUID.

  The issue here is that this both LABEL and UUID could collide with a
  local filesystem.   Perhaps a previous install left a filesystem
  labeled "rootfs" that happened to match the filesystem of the
  iscsi_target_name and now using "root=LABEL=rootfs".  The same is
  possible with UUID.

  There needs to be some way to specify explicitly:
     root=iscsi_target_name=some-iscsi-target-name that would make the iscsi initialization code guaranteed to boot with the appropriate root device independent of whatever local filesystems might have.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.10
  Package: open-iscsi 2.0.873-3ubuntu5
  ProcVersionSignature: Ubuntu 3.5.0-17.28-generic 3.5.5
  Uname: Linux 3.5.0-17-generic x86_64
  ApportVersion: 2.6.1-0ubuntu6
  Architecture: amd64
  Date: Mon Nov  5 15:25:48 2012
  MarkForUpload: True
  ProcEnviron:
   LANGUAGE=en_US:
   TERM=screen
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: open-iscsi
  UpgradeStatus: No upgrade log present (probably fresh install)

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