How to reload udev rules without reboot?

Question

How should one reload udev rules, so that newly created one can function?

I'm running Arch Linux, and I don't have a udevstart command here.

Also checked /etc/rc.d, no udev service there.

Answer 1

# udevadm control --reload-rules && udevadm trigger

Answer 2

Udev uses the inotify mechanism to watch for changes in the rules directory, in both the library and in the local configuration trees (typically located at /lib/udev/rules.d and /etc/udev/rules.d). So most of the time you don't need to do anything when you change a rules file.

You only need to notify the udev daemon explicitly if you're doing something unusual, for example if you have a rule that includes files in another directory. Then you can use the usual convention for asking daemons to reload their configuration: send a SIGHUP (pkill -HUP udevd). Or you can use the udevadm command: udevadm control --reload-rules.

However, beware that different versions of udev have historically had different triggers for reloading the rules automatically. So if in doubt, call udevadm control --reload-rules: it won't do any harm anyway.

The udev rules are only applied when a device is added. If you want to reapply the rules to a device that is already connected, you need to do this explicitly, by calling udevadm trigger with the right options to match the device(s) whose configuration has changed, e.g. udevadm trigger --attr-match=vendor='Yoyodyne' --attr-match=model='Frobnicator 300'.

Answer 3

I'm adding this because some day I will need it... again.

Sometimes you get an incorrect matching of ethernet device numbers and MAC addresses. Sometimes this is really important, like when running in a VM and each device is assigned to a different VLAN.

1. Bring the network interfaces down, then
2. modify /etc/udev/rules.d/70-persistent-net.rules (or its equivalent)
3. re-load with udevadm control --reload-rules
4. re-trigger with udevadm trigger --attr-match=subsystem=net
5. bring the network interfaces up.

I was surprised how well this worked.

Answer 4

I am not sure if this applies, and this is definitely an older post but it came up pretty high my web search for udev info so I thought I might share some knowledge.

You can trigger udev rules manually for specific devices. This applies only to redhat-related distros (centos fedora etc etc etc)

Once you make the relevant changes in your rules file (/etc/udev/rules.d/whateveryoucalledyourrules), you can echo change in to the device's uevent.

echo change > /sys/block/devname/partname1/uevent

This will force a udev rule reading for ONLY this device. Much better, and more targeted in my opinion.

Answer 5

For me, below command sequence has worked as it is desired.

I have done modifications in /etc/udev/rules.d/70-persistent-net.rules to change the eth number and to reload them without rebooting.

/etc/init.d/networking stop
/etc/init.d/udev stop
udevadm control --reload-rules
/etc/init.d/udev start
/etc/init.d/networking start

By following this, It was successfully loaded in run time without rebooting the machine.

Any suggestion or recommendations on this are welcome, as I have discovered this on my own by reading the man pages.

Answer 6

I'm adding the correct answer here because it took me a while to notice it in the comment from @enthusiasticgeek. All you need to do (assuming you are on the console of the server - clearly this is bad to do if you are ssh'd in!):

1. Get a list of the interface module(s) being used:

cat /etc/udev/rules.d/70-persistent-net.rules | grep "PCI device" | perl -pe 's/.*\((\w+)\).*/$1/g'| uniq

In my case, it's igb, so it prints just that.

2. type sudo rmmod igb (replace igb with your card driver obtained from step 1.

next, edit /etc/udev/rules.d/70-persistent-net.rules as needed, then load the module again using modprobe igb, again replacing igb with yours.

Answer 7

This is a slight change from the main answer: sudo seemed to be required for me on both commands.

Anecdotal evidence: doing sudo udevadm trigger took ~2 sec, but doing it withOUT sudo took only ~0.2 sec. So clearly they are not doing the same thing for me. Do this instead:

sudo udevadm control --reload-rules
sudo udevadm trigger

And then lastly (per the 2nd link below), unplug your device and plug it back in.

References:

1. How to reload udev rules without reboot?
2. https://askubuntu.com/questions/1048870/permission-denied-to-non-root-user-for-usb-device/1187646#1187646

See comments under both of the answers above as well.

Answer 8

in case of multiple networks

cat /etc/udev/rules.d/70-persistent-net.rules | grep "PCI device" | awk '{print $NF}'|sed -e 's/(//g' -e 's/)//g'| uniq > /tmp/listnet
rm -rf /etc/udev/rules.d/70-persistent-net.rules 
for i in $(cat /tmp/listnet); do rmmod $i; modprobe $i;done
service network restart
rm -rf /tmp/listnet