Difference between udev and udevadm

nisargshah95 · 02-06-2015, 11:14 AM

Hi. I am relatively new to linux systems. I recently jumped on an endeavor to install a vanilla kernel (3.18.5) from the kernel website. Its Documentation/Changes file mentions the minimum version requirements of the packages needed. For udev, it mentioned

Code:

udevd --version

to check the version number. But looking around I found for Fedora its

Code:

udevadm --version

(I'm using Fedora Workstation 21 64-bit). Is there any fundamental difference between these two utilities? Any explanation would be helpful.

rtmistler · 02-06-2015, 12:12 PM

udevadm(8) is the the udev management tool used for configuring it and how it behaves.

udevd(8) is the udev daemon, that which has it's behavior changed by udevadm

Links above bring you to the manual pages.

nisargshah95 · 02-06-2015, 12:25 PM

Then shouldn't

Code:

udevd --version

also return the version number? I'm sorry I am clueless here.

rtmistler · 02-06-2015, 12:33 PM

Quote:

Originally Posted by nisargshah95

Then shouldn't

Code:

udevd --version

also return the version number? I'm sorry I am clueless here.

Yep, unless it's not install. You could try

Code:

which udevd

to see if the command exists at all on your system.

nisargshah95 · 02-06-2015, 12:39 PM

I think it doesn't

Code:

[nisarg@localhost linux-3.18.5]$ which udevd
/usr/bin/which: no udevd in (/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/home/nisarg/.local/bin:/home/nisarg/bin)

RockDoctor · 02-06-2015, 03:52 PM

From Fedora Rawhide (FWIW):

Code:

~$ ps aux | grep udev
root       406  0.0  0.1  43940  3988 ?        Ss   15:09   0:00 /usr/lib/systemd/systemd-udevd
a         2159  0.0  0.0 113096   848 pts/0    S+   15:48   0:00 grep --color=auto udev

Code:

~$ rpm -q --whatprovides /usr/lib/systemd/systemd-udevd 
systemd-218-4.playground.fc22.x86_64

Code:

~$ udevadm --version
218