[Bug 2040153] [NEW] Network Manager will not remove Netplan YAMLs when connections are deleted

[Danilo Egea Gondolfo]

Public bug reported:

When a connection is deleted using any NM facility, libnetplan is
failing to delete the YAML file. Because of that, the connection will be
recreated when "netplan generate" runs again.

This is probably being caused by a combination of two things. First, the
NM's systemd unit has this setting "ProtectSystem=true", which will
mount /usr as read-only for NM. Second, we migrated the default
"00-network-manager-all.yaml" file to, /usr/lib/netplan recently [1].
When libnetplan tries to open this file for writing, the open system
fails with EROFS:

---
22517 openat(AT_FDCWD, "/lib/netplan/00-network-manager-all.yaml", O_WRONLY|O_CREAT|O_TRUNC, 0600) = -1 EROFS (Read-only file system)
22517 write(2, "netplan_delete_connection: Canno"..., 76) = 76
---


[1] - https://launchpad.net/ubuntu/+source/ubuntu-settings/23.10.1

** Affects: netplan.io (Ubuntu)
     Importance: Critical
         Status: Triaged

** Affects: network-manager (Ubuntu)
     Importance: Critical
         Status: Triaged

** Affects: netplan.io (Ubuntu Mantic)
     Importance: Critical
         Status: Triaged

** Affects: network-manager (Ubuntu Mantic)
     Importance: Critical
         Status: Triaged


** Tags: foundations-todo

** Also affects: netplan.io (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: network-manager (Ubuntu Mantic)
   Importance: Undecided
       Status: New

** Also affects: netplan.io (Ubuntu Mantic)
   Importance: Undecided
       Status: New

** Changed in: netplan.io (Ubuntu Mantic)
   Importance: Undecided => Critical

** Changed in: network-manager (Ubuntu Mantic)
   Importance: Undecided => Critical

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https://bugs.launchpad.net/bugs/2040153

Title:
  Network Manager will not remove Netplan YAMLs when connections are
  deleted

Status in netplan.io package in Ubuntu:
  Triaged
Status in network-manager package in Ubuntu:
  Triaged
Status in netplan.io source package in Mantic:
  Triaged
Status in network-manager source package in Mantic:
  Triaged

Bug description:
  When a connection is deleted using any NM facility, libnetplan is
  failing to delete the YAML file. Because of that, the connection will
  be recreated when "netplan generate" runs again.

  This is probably being caused by a combination of two things. First,
  the NM's systemd unit has this setting "ProtectSystem=true", which
  will mount /usr as read-only for NM. Second, we migrated the default
  "00-network-manager-all.yaml" file to, /usr/lib/netplan recently [1].
  When libnetplan tries to open this file for writing, the open system
  fails with EROFS:

  ---
  22517 openat(AT_FDCWD, "/lib/netplan/00-network-manager-all.yaml", O_WRONLY|O_CREAT|O_TRUNC, 0600) = -1 EROFS (Read-only file system)
  22517 write(2, "netplan_delete_connection: Canno"..., 76) = 76
  ---

  
  [1] - https://launchpad.net/ubuntu/+source/ubuntu-settings/23.10.1

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