How to set zfs module parameters

[jfroy]

With siderolabs/extensions#573, the udev rule for zfs loads the module with no parameters:

❯ talosctl read /usr/lib/udev/rules.d/90-zfs.rules 
SUBSYSTEM!="block|misc", GOTO="zfs_end"
ACTION!="add|change", GOTO="zfs_end"

ENV{ID_FS_TYPE}=="zfs", RUN+="/sbin/modprobe zfs"
ENV{ID_FS_TYPE}=="zfs_member", RUN+="/sbin/modprobe zfs"

KERNEL=="null", SYMLINK+="root"
SYMLINK=="null", SYMLINK+="root"

KERNEL=="zfs", MODE="0666", OPTIONS+="static_node=zfs"

LABEL="zfs_end"

I need to set zfs module parameters. Doing it in the machineconfig (machine.kernel.modules) does not work as that job runs after the udev init job.

So what's the "Talosy way" to do this?

• Override the udev rule via the mc to add module parameters (install file in /etc/udev/rules.d/)?
• Install a modprobe conf file via the mc (install file in /etc/modprobe.d/*.conf)?
• Set zfs.<option> in the kernel command line via the mc?

[jfroy]

I think the modprobe.d/*.conf and udev/rules.d/ methods are not possible because you cannot install files outside of /var with the mc.

create operation not allowed outside of /var: "/etc/modprobe.d/zfs.conf"

[smira]

We don't have a good answer today (unfortunately), we need to figure out something here.

Machine config should apply before udev, but it's racy.

[jfroy]

We don't have a good answer today (unfortunately), we need to figure out something here.

Machine config should apply before udev, but it's racy.

Well you basically can't use the machine config because it won't let you write outside of /var. So I'm testing kernel command line, which should not race with udev since those are applied by the bootloader or embedded in the UKI.

[jfroy]

Using kernel commandline works well enough.

[frezbo]

I think we just need to fix our .machine.kernel.modules to apply the kernel parameters even if the module is already loaded, we'd probably need to fix this in the upstream kmod library