Adding net.ifnames=0 to image-factory extra kernel arguments is not being respected

[budimanjojo]

Bug Report

I tried a fresh install in a VM with only net.ifnames=0 extra kernel command-line args using image-factory and it gives me factory.talos.dev/installer/6905bc709e5947573a4ec2d11723b58882936d3d0e15c708f7d78f0c689684a5:v1.5.5 installer URL.
I put that into machine config and do talosctl apply-config --insecure into the machine, did a talosctl bootstrap and then talosctl get addresses after it finishes. The result shows enx56e63648f898 as the interface name instead of eth0.

I'm not sure if this only happens for net.ifnames=0 or all kernel arguments.

[frezbo]

This is expected, since these only gets added for iso or pxe boot, needs to add the same in machine.install.extraKernelArgs

[budimanjojo]

So kernel args are useless for install image?

If I'm booting from an iso image downloaded from the image-factory with the kernel args, then do installation without specifying machine.install.extraKernelArgs, does that kernel args also got deleted on reboot?

[frezbo]

If I'm booting from an iso image downloaded from the image-factory with the kernel args, then do installation without specifying machine.install.extraKernelArgs

I believe it should preserve

[budimanjojo]

This makes it even weirder if the kernel arguments in the downloaded ISO is permanent and can't be removed/changed.
Is it really the intended behavior and not something that should be improved?
a. If I download the ISO from the github releases (bare iso without any extension and kernel args), then I use the image-factory generated installer to install Talos to the machine and expecting the image will enable the kernel arguments I specify in the image-factory.
b. If I download the ISO from image-factory with the kernel arguments I wanted at the moment, I can't remove it in the future unless I boot from a brand new ISO image.

[frezbo]

This makes it even weirder if the kernel arguments in the downloaded ISO is permanent and can't be removed/changed.

net.ifnames get special treatment, it's one of the ones that gets preserved. Other's gets dropped:

For what it's worth, these are the only ones that gets preserved:

• siderolink.api
• talos.events.sink
• talos.logging.kernel
• em.events_url
• talos.dashboard.disabled
• net.ifnames

For a -> installer never will have any kernel arguments, if you'd need extra that needs to be part of machine config

For b -> Starting with Talos 1.6 we support removing kernel args with -<key> for removing all and -<key>=<value> to remove an exact one

[budimanjojo]

thanks! this is clear now. I'll close this issue.

[smira]

The fact that installer ignores extra args is documented here: https://www.talos.dev/v1.5/learn-more/image-factory/#restrictions

Image Factory still accepts a schematic with extra args for an installer, so that you can use same schematic say for ISO and installer, this way ISO captures initial boot args, and installer later on doesn't touch it. (So that there's no need to create a separate schematic for an installer).

To add some more confusion to the issue, SecureBoot installer actually accepts extra args, as they are part of the signed payload of the boot asset, and install.extraKernelArgs is ignored in SecureBoot mode.

[budimanjojo]

@smira thanks for the explaination.This is indeed really confusing. 😅