On 8/3/20 6:50 PM, Simon Matter via CentOS wrote:
Hi,
I've got a task to have a small number of laptops netboot Linux over WiFi. The kernel is loaded off the USB stick of cource, it's off topic for now.
The WPA-supplicant daemon is started early by dracut off initrd. It works. Mostly.
The problem is that upon shutdown systemd terminates all the processes FIRST and unmounts filesystems NEXT.
Guess what? Upon termination, wpa-supplicant brings the wireless interface down and the system hangs being unable to unmount now-defunct NFSroot.
Short answer:
Looks like this should be fixed in systemd or its configuration.
Long answer is the one I already gave you on centos-devel. I post it here because someone may have deeper knowledge of what exactly goes on:
What I'm wondering here is, do you see the hangs because of wpa_supplicant was terminated and therefore also the wireless interface is down, or do you see the hangs because networking is already completely down.
It's because of wpa_supplicant. When I run the same config over wired network, it shuts down gracefully.
A dirty solution I found is to kill (-9) wpa_supplicant daemon right before shutdown. WiFi keeps running for a second it requires to do a graceful NFS unmount.
Best regards, Dmitry Mikhailov