28.11.2024 21:49, Thomas HUMMEL wrote:
On 11/25/24 3:07 PM, Thomas HUMMEL wrote:
On 11/25/24 2:50 PM, Andrei Borzenkov wrote:
On Mon, Nov 25, 2024 at 4:39 PM Thomas HUMMEL
<thomas.hummel@xxxxxxxxxx> wrote:
Hello,
I've got a somehow silly question:
Am I right to think that a service unit I wrote meant to format and
mount a localdisk at boot having the following properties :
Wants=local-fs.target
Before=local-fs.target
+ DefaultDepenencies=no may be racing against udevd in a way the device
(/dev/nvme0) would not be there yet ?
Yes.
If so, would adding After=systemd-udevd suffice ?
No.
Either invoke your service from within udev rule (SYSTEMD_WANTS or
even systemctl start), or configure your service with
Requires=dev-nvme0.device
After=dev-nvme0.device
Actually, you probably want to do it even when invoking by udev rules.
This assumes that /dev/nvme0 is reasonably stable. You may want to use
some other available /dev/disk/by-... stable alias.
Ok, thanks for your reply.
Hello,
coming back to the topic (sorry, I had an actual physical issue with the
device which blurred my analysis):
1. On a system where /dev/nvme0, /dev/nvme0n1 and /dev/nvme0n1p1 files
exist, systemctl list-units --type=device | grep -i nvme only list
physical path ones such as
sys-devices-pci0000:a0-0000:a0:03.1-0000:a1:00.0-nvme-nvme0-nvme0n1.device
for instance.
Did you assume something I do not have by evoking dev-nvme.device ?
Try
systemctl -t device -a
2. on the udev rule way of doing things:
man states:
"Starting daemons or other long-running processes is not appropriate for
udev; the forked processes, detached or not, will be unconditionally
killed after the event handling has finished."
and
"Note that running programs that access the network or mount/unmount
filesystems is not allowed inside of udev rules, due to the default
sandbox that is enforced on systemd-udevd.service."
What defines "event handling has finished". Typically the external
program I'd consider running would be a) partition disk b) format (mkfs)
disk : would that be considered a long-running process in the context of
udev ?
Finally the last statement obviouly means my program could not - as the
current service I'm using does - mount the partition - but this could be
handled elsewhere
I never suggested doing it from within udev rule. I suggested starting
systemd service which runs outside of event handler.
