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GNUser

Member

Registered: 2017-03-16

Posts: 570  

what starts the eudev service? [SOLVED]

Even though eudev is a service (sudo service eudev status produces output and /etc/init.d/eudev exists), I cannot find a corresponding link in /etc/rc2.d (i.e., none of the links have eudev, udev, or udevd in the name).

What starts the eudev service and how?

Last edited by GNUser (2018-08-29 23:52:58)

ralph.ronnquist

Administrator

From: Battery Point, Tasmania, AUS

Registered: 2016-11-30

Posts: 1,251  

Re: what starts the eudev service? [SOLVED]

Looking at my own system (ascii), the story is something like the following.

The process is named udevd.

It's first started by its pre-pivot init-top/udev script, in initramfs. That process is then killed at the end of the pre-pivot init sequence, by its  init-bottom/udev script, still in initramfs.

Next it has its init link /etc/rcS.d/S0?eudev (or possibly /etc/rcS.d/S0?udev) for starting udevd in the post-pivot init sequence.

The pre-pivot start up includes a forced traversal of the /sys tree through a udevadm trigger --action=add command, and then that init-top/udev script also waits for udevadm settle to return, before it "pokes" extra on scsi devices, if any, followed by an optional additional timeout in some circumstances. Further, the init-bottom/udev script at the end of pre-pivot init merely kills the pre-pivot udevd process, and then moves the pre-pivot /dev to be available as post-pivot /dev.

Note that pre-pivot init is a script, usually a copy of /usr/share/initramfs-tools/init, and it ends with an exec run-init ..., which becomes the post-pivot init process (or a panic, if exec fails).

GNUser

Member

Registered: 2017-03-16

Posts: 570  

Re: what starts the eudev service? [SOLVED]

Thank you, ralph.ronnquist. I'm embarrassed that S0?eudev is in /etc/rcS.d/ (instead of in /etc/rc2.d/) but I didn't know to look there. A careful look at /etc/inittab would have clued me in to the fact that the /etc/rcS.d/ directory exists and its scripts run before those in /etc/rc?.d/.

You really took it to the next level with the information about the pre-pivot start up. In my mind all that is simply "initramfs stage"--the fine details of which I never considered or even heard of before. Thank you very much for such an insightful answer.

Last edited by GNUser (2018-08-30 14:28:39)

fsmithred

Administrator

Registered: 2016-11-25

Posts: 2,486  

Re: what starts the eudev service? [SOLVED]

Here's a picture of Ralph, in case anyone was wondering what he looks like.

https://orig00.deviantart.net/60a0/f/20 … 3iiyfb.jpg

GNUser

Member

Registered: 2017-03-16

Posts: 570  

Re: what starts the eudev service? [SOLVED]

That's what I thought.