[Bug 2122583] Re: Current questing daily installation hangs on NW config screen

[Olivier Gayot]

My previous understanding was flawed. I anticipated that renaming the
00-installer-config.yaml to 10-livefs.yaml (because 00-installer-
config.yaml is special to Subiquity) would work but it doesn't.

The main problem is that Subiquity and netplan (or the underlying
network daemon, really) have different understandings of priority when
multiple network configs match for the same interface. (obviously
netplan should be considered right and ideally Subiquity should defer to
netplan).

For instance, in the following situation:

/etc/netplan/00-installer-config.yaml
network: 2
  version:
  ethernets:
    zz-all-en:
      match:
        name: "en*"
      dhcp4: true

/etc/netplan/50-cloud-init.yaml
network
  version: 2
  ethernets:
     enc600:
       addresses: [10.245.236.23/24]

1. netplan (systemd-networkd) decides to honor the static addressing from 50-cloud-init.yaml.
Indeed the generated conf files for systemd-networkd are:
   * /run/systemd/network/10-netplan-enc600.network
   * /run/systemd/network/10-netplan-zz-all-en.network
Quote from systemd.network(5): 
> The network file contains a [Match] section, which determines if a given network file may
> be applied to a given interface; and a [Network] section specifying how the interface
> should be configured. The first (in alphanumeric order) of the network files that matches
> a given interface is applied, all later files are ignored, even if they match as well.

so 10-netplan-enc600.network (generated from /etc/netplan/50-cloud-
init.yaml) is honored.

2. Subiquity decides to honor DHCP addressing because it takes the first
matching config from /etc/netplan/*.yaml (and it reads 00-installer-
config.yaml before 50-cloud-init.yaml).

In an ideal world, Subiquity should use the same logic as netplan but
netplan defers to the underlying network daemon so that will be a
challenging task. Maybe going forward Subiquity should read the
currently active network config (e.g., netplan status?) rather than
parsing /etc/netplan?

In any case, we have a few options today:

* Rename 00-installer-config.yaml to 60-livefs.yaml. This will not impact netplan but will impact make Subiquity give more priority to 50-cloud-init.yaml
* Drop 00-installer-config.yaml completely
* Change Subiquity so that it guesses better which config will be used after netplan apply.

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https://bugs.launchpad.net/bugs/2122583

Title:
  Current questing daily installation hangs on NW config screen

Status in Ubuntu on IBM z Systems:
  New
Status in subiquity package in Ubuntu:
  Incomplete

Bug description:
  Today I wanted to use the latest questing daily to test an installation with now kernel 6.17 using an interactive install.
  As usual, I've configured static IPs in the basic network setup (casper).
  And when I then reach the "Network configuration" screen, I notice that DHCPv6 is suddenly selected (which was not the case in the past), and I cannot do anything anymore, probably due to the loss of the static IP configuration.
  Due to this I can also not login to the system and save the logs or anything like that.

  Hence I just attach a screenshot ...

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