[Bug 2064201] Re: Use Debian-specific partx path in kpartx rule

[Chengen Du]

@sergiodj Apologies for the oversight in not providing a detailed test
plan earlier. I've now updated it. Thank you for your help.

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https://bugs.launchpad.net/bugs/2064201

Title:
  Use Debian-specific partx path in kpartx rule

Status in multipath-tools package in Ubuntu:
  New
Status in multipath-tools source package in Bionic:
  In Progress
Status in multipath-tools source package in Focal:
  Fix Committed

Bug description:
  [Impact]
  The issue arises from the installation of the udev rules file /lib/udev/rules.d/68-del-part-nodes.rules by kpartx.
  This file references /usr/sbin/partx, but on Debian, partx is located in /usr/bin.
  This incorrect path leads to the following error:
  systemd-udevd[3302364]: sdrg: Process '/usr/sbin/partx -d --nr 1-1024 /dev/sdrg' failed with exit code 1.

  [Fix]
  The upstream has a patched fix available.
  https://salsa.debian.org/linux-blocks-team/multipath-tools/-/blob/master/debian/patches/0003-kpartx-rules-use-Debian-specific-partx-path.patch?ref_type=heads

  [Test Plan]
  1. Prepare a VM with two NICs and setup an iSCSI target
  root at focal:~# cat /etc/tgt/conf.d/iscsi.conf 
  <target iqn.2024-05.storage.com:disk1>
  	backing-store /dev/sdX
  </target>
  2. Prepare another VM and execute iSCSI discovery and login
  iscsiadm -m discovery -t sendtargets -p XXX
  iscsiadm -m node --login
  3. Show multipath topology
  multipath -ll
  4. Use the following command to trigger the udev rule
  udevadm trigger --subsystem-match="block" --name-match=sdX
  5. Confirm that there is no following error in /var/log/syslog
  systemd-udevd[1788]: sdX: Process '/usr/sssbin/partx -d --nr 1-1024 /dev/sdX' failed with exit code 1.

  [Where problems could occur]
  The patch specifically targets a single udev rule responsible for deleting partition devnodes for slave devices associated with specific aggregate devices, like multipath. This modification solely adjusts the path of the partx command. If the path is incorrect, the devnode will persist.

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