Adding new NIC gives these network devices: eth0, eth1_rename.
1. Having a system with one or more NICs.
2. They are correct listed in /etc/udev/rules.d/70-persistent-net.rules as eth0 (eth1, eth2, ...).
3. Adding new NIC to the system.
4. udev takes 30sec more.
5. you get devices: eth0 eth1_rename
6. The tmp-rules file (/dev/.udev/tmp-rules--70-persistent-net.rules) contains a rule for the new device, but as name for new device it has one which was already given to another NIC in normal rules file.
Rebooting will not solve the problem, as at reboot-time the tmp-rule file is also getiing saved to normal location.
That means every boot udev will take its 30sec more, and leave at least one eth?_rename interface.
1. delete rule-files:
2. Edit rule file(s) to contain unique device names.
Bug is caused by this:
code to look for already used device-names tests the rules file for existance before getting its info out of there.
So far so good. But in our case (root-fs still read-only) it only checks tmp-location /dev/.udev/tmp-rules--... which for sure is not existing at that point. Thus device-logic can accept already used device, and udev rename logic fight with two or more interfaces to get that name.
Fixed in udev-104-r11 by just deleting that check - sed can cope with non-existing files, will only print a warning (that gets redirected to /dev/null by udev).