View source for Network Setup Tips

__TOC__

== NST Script: nstnetcfg ==
See page: '''[[HowTo_Setup_A_Server_With_Multiple_Network_Interface_Adapters_Using:_"nstnetcfg" | HowTo Setup a Server With Multiple Network Interface Adapters Using: "nstnetcfg"]]''' for a simplified means of setting up networking on an NST system.

== Accessing Network Configuration Files ==

To easily access the network configuration files, simply use the '''[http://www.gnu.org/software/bash bash]''' alias: '''"cdnet'''":

<div class="screen">
<div class="userInput"><span class="prompt">[root@probe ~]# </span>cdnet</div>
<pre class="computerOutput">
[root@probe network-scripts]# 
</pre>
<div class="userInput"><span class="prompt">[root@probe ~]# </span>pwd</div>
<pre class="computerOutput">
/etc/sysconfig/network-scripts
[root@probe network-scripts]# 
</pre>
</div>

&nbsp;

== NST Script: nstnetcfg ==
[[HowTo_Setup_A_Server_With_Multiple_Network_Interface_Adapters_Using:_"nstnetcfg"]]

== How To Specify A Host Name To A DHCP Server ==
Some times it is desirable to specify a ''host name'' at the '''DHCP Client''' to be recognized by the '''DHCP Server'''. This will allow for local host names to be resolved by their respective name on the local '''LAN'''. This works well with a [http://www.dd-wrt.com DD-WRT] enabled [http://www.linksys.com LinkSys] router and [http://www.isc.org/software/bind bind].

To do this, add the following line to your network configuration file (Example for: '''eth0''' - We will use file: "'''/etc/sysconfig/network-scripts/ifcfg-eth0'''" and request that the '''DHCP''' server set this system's host name to: "'''emachine'''".):

<pre class="programListing">
DHCP_HOSTNAME=<Your desired host name for this NST DHCP client>
</pre>

Both the "'''network'''" service and the [http://live.gnome.org/NetworkManager NetworkManager] service support this setting for '''DHCP'''.

<div class="screen">
  <div class="screenTitle">''Listing:'' "/etc/sysconfig/network-scripts/ifcfg-eth0"</div>
  <div class="userInput"><span class="prompt">[root@probe-biostar network-scripts]# </span>cat "/etc/sysconfig/network-scripts/ifcfg-eth0"</div>
  <pre class="computerOutput">
#
# DHCP Client Config: eth0
DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes

#
# Disable capabilities security feature when running dhclient so we
# can run the NST dhclient exit hook script: "/etc/dhcp/dhclient.d/nst.sh".
DHCLIENTARGS="-nc"

#
# Specify the 'dhclient' host-name option (-H) to send to the DHCP server.
DHCP_HOSTNAME=emachine
</pre>
</div>

&nbsp;

== How To Permanently Set The Host Name Of Your NST System ==
To do this, add/change the following line to the system configuration file: "'''/etc/sysconfig/network'''"

<pre class="programListing">
HOSTNAME=<your desired host name for this NST system>
</pre>

[http://live.gnome.org/NetworkManager NetworkManager] will be ''notified'' of this change and automatically set the system "'''hostname'''". The example below sets the system host name to: "'''emachine'''". Typically, if this system is a '''DHCP''' client, both the "'''DHCP_HOSTNAME'''" discussed above and the "'''HOSTNAME'''" entries are set identically.

<div class="screen">
  <div class="screenTitle">''Listing:'' "/etc/sysconfig/network"</div>
  <div class="userInput"><span class="prompt">[root@probe-biostar sysconfig]# </span>cat "/etc/sysconfig/network"</div>
  <pre class="computerOutput">
NETWORKING=yes
HOSTNAME=emachine
NOZEROCONF=yes
</pre>
</div>

A system reboot can be done to verify all changes.

<div class="centerBlock"><div class="noteMessage">'''Note on Setting the Host Name when Using DHCP to get the IP Address:''' NST is configured to run the '''dhclient''' exit hook script: "'''/etc/dhcp/dhclient.d/nst.sh'''". This script will try to automatically set the system's host name based on results from '''DHCP'''. Avoid using "'''probe-'''" as the first 6 characters in the "'''HOSTNAME'''" parameter above (e.g., '''probe-sys1''' - Instead use: '''sys1-probe'''). These characters are ''reserved'' by NST.</div></div>

&nbsp;

== Configuring A Static IP Address ==

If the network your interface is connected to does not have a '''DHCP''' server, you will need to configure your system to use a static '''IP''' address. The following shows the contents of file: "'''/etc/sysconfig/network-scripts/ifcfg-eth0'''" which is used to assign a static '''IP''' address of: "'''192.168.12.100'''" to '''eth0''' (an Ethernet interface):

<pre class="programListing">
DEVICE=eth0
BOOTPROTO=static
IPADDR=192.168.12.100
NETMASK=255.255.255.0
NETWORK=192.168.12.0
BROADCAST=192.168.12.255
GATEWAY=192.168.12.1
ONBOOT=yes
</pre>

<div class="centerBlock"><div class="noteMessage">'''Note 1:''' The above assumes that the gateway machine for the network has an '''IP''' address of: "'''192.168.12.1'''" on network: "'''192.168.12.0/24'''".<br/><br />'''Note 2:''' Make sure the '''NetworkManager'''" service is disabled: '''systemctl disable NetworkManager.service;'''<br /><br />'''Note 3:''' Make sure the "'''network'''" service is enabled: '''systemctl enable network.service;'''
</div></div>

&nbsp;

== Configuring A Stealth Network Interface ==

In order to configure a stealth (i.e., A network interface with a non-binding IP Address) network interface set the '''BOOTPROTO''' setting to: "'''none'''".  Example: Make network interface: "'''eth1'''" at stealth interface using this minimal configuration:

<pre class="programListing">
DEVICE=eth1
BOOTPROTO=none
ONBOOT=yes
</pre>

&nbsp;

== Restarting the Network Service ==

After editing any network configuration file, you should restart the ''network'' service as shown below:

<div class="screen">
  <div class="screenTitle">Restarting the Network Service (service command)</div>
  <div class="userInput"><span class="prompt">[root@probe-biostar network-scripts]# </span>service network restart</div>
  <pre class="computerOutput">
[root@tmobile network-scripts]# service network restart
Shutting down interface eth0:                              [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:                                [  OK  ]
</pre><div class="userInput"><span class="prompt">[root@probe-biostar network-scripts]# </span></div>
</div>

For "'''NST 15'''" and above use the '''[http://0pointer.de/public/systemd-man/systemctl.html systemctl]''' command:

<div class="screen">
  <div class="screenTitle">Restarting the Network Service (systemctl command)</div>
  <div class="userInput"><span class="prompt">[root@probe-biostar network-scripts]# </span>systemctl restart network.service</div>
  <pre class="computerOutput">
[root@tmobile network-scripts]# systemctl restart network.service
</pre><div class="userInput"><span class="prompt">[root@probe-biostar network-scripts]# </span></div>
</div>

&nbsp;

== Display Routing Table ==

The following command can be used to display your network routing table (the ''-n'' option was included to prevent the ''route'' command from trying to resolve names):

<div class="screen">
  <div class="screenTitle">Display Routing Table</div>
  <div class="userInput"><span class="prompt">[root@dhcp121 ~]# </span>route -n</div>
  <pre class="computerOutput">
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 eth0
</pre><div class="userInput"><span class="prompt">[root@dhcp121 ~]# </span></div>
</div>

&nbsp;

== IP Aliasing (Multi-Net) ==
=== Overview ===
An '''[http://www.faqs.org/docs/Linux-mini/IP-Alias.html IP Alias]''' allows you to configure multiple '''IP Addresses''' onto a physical device ('''NIC'''). '''IP aliasing''' is known as network layer virtual hosting. It is common to use an '''IP Aliases''' with '''[http://httpd.apache.org/docs/2.0/vhosts/ Apache Virtual Hosting].

=== HowTo Add An IP Alias ===

<div class="screen">
  <div class="screenTitle">IP Alias Add Example: (NIC: p5p1, Alias: p5p1:0)</div>
  <div class="userInput"><span class="prompt">[root@shopper2 ~]# </span>ifconfig</div>
  <pre class="computerOutput">
lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:580 errors:0 dropped:0 overruns:0 frame:0
          TX packets:580 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:44887 (43.8 KiB)  TX bytes:44887 (43.8 KiB)

p5p1      Link encap:Ethernet  HWaddr E0:69:95:B1:6E:BF  
          inet addr:10.222.222.10  Bcast:10.222.222.255  Mask:255.255.255.0
          inet6 addr: fe80::e269:95ff:feb1:6ebf/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:146101 errors:0 dropped:19 overruns:0 frame:0
          TX packets:71495 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:80187453 (76.4 MiB)  TX bytes:44001889 (41.9 MiB)
          Interrupt:46 Base address:0x6000 
  </pre>
  <div class="userInput"><span class="prompt">[root@shopper2 ~]# </span>ifconfig p5p1:0 10.222.222.83/24</div>
  <div class="userInput"><span class="prompt">[root@shopper2 ~]# </span>ifconfig</div>
  <pre class="computerOutput">
lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:580 errors:0 dropped:0 overruns:0 frame:0
          TX packets:580 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:44887 (43.8 KiB)  TX bytes:44887 (43.8 KiB)

p5p1      Link encap:Ethernet  HWaddr E0:69:95:B1:6E:BF  
          inet addr:10.222.222.10  Bcast:10.222.222.255  Mask:255.255.255.0
          inet6 addr: fe80::e269:95ff:feb1:6ebf/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:146101 errors:0 dropped:19 overruns:0 frame:0
          TX packets:71495 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:80187453 (76.4 MiB)  TX bytes:44001889 (41.9 MiB)
          Interrupt:46 Base address:0x6000

p5p1:0    Link encap:Ethernet  HWaddr E0:69:95:B1:6E:BF  
          inet addr:10.222.222.83  Bcast:10.222.222.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:46 Base address:0x6000 
  </pre><div class="userInput"><span class="prompt">[root@shopper2 ~]# </span></div>
</div>

The '''IP Alias''' command above produced a virtual host address for the '''p5p1''' network interface using IP Address: "'''10.222.222.83'''". '''IP Aliases''' are referred to by appending "''':n'''" to the actual network interface device, in which "'''n'''" is an integer. In our example, we created the '''IP Alias''' on NIC: "'''p5p1'''" , with alias number "'''Zero (0)'''".

All network statistics associated with each '''IP Alias''' interface are combined with the physical network interface. To get individual statistics for an '''IP Aliased Interface''' then accounting rules would need to be used through the [http://en.wikipedia.org/wiki/Iptables iptables] command.

=== HowTo Remove An IP Alias ===
To remove an '''IP Alias''' use the '''ifconfig''' command "'''down'''" option:  

<div class="screen">
  <div class="screenTitle">IP Alias Remove Example1: (NIC: p5p1, Alias: p5p1:0)</div>
  <div class="userInput"><span class="prompt">[root@shopper2 ~]# </span>ifconfig p5p1:0 down</div>
  <pre class="computerOutput">  </pre><div class="userInput"><span class="prompt">[root@shopper2 ~]# </span></div>
</div>

&nbsp;

=== HowTo Permanently Add An IP Alias ===
This procedure uses the "'''network'''" service. The following shows the contents of file: "'''/etc/sysconfig/network-scripts/ifcfg-p5p1:0'''" which is used to assign a static '''IP Alias''' address of: "'''10.222.222.83'''" to network interface: "'''p5p1:0'''"

<pre class="programListing">
DEVICE=p5p1:0
BOOTPROTO=static
IPADDR=10.222.222.83
NETMASK=255.255.255.0
NETWORK=10.222.222.0
BROADCAST=10.222.222.255
GATEWAY=10.222.222.1
ONBOOT=yes
</pre>

<div class="centerBlock"><div class="noteMessage">'''Note 1:''' The above assumes that the gateway machine for the network has an '''IP''' address of: "'''10.222.222.1'''" on network: "'''10.222.222.0/24'''".<br/><br />'''Note 2:''' Make sure the '''NetworkManager'''" service is disabled: '''systemctl disable NetworkManager.service;'''<br /><br />'''Note 3:''' Make sure the "'''network'''" service is enabled: '''systemctl enable network.service;'''
</div></div>


== '''Create Predictable Network Interface Names''' ==
Some information in this section was derived from the sites: '''[http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/ freedesktop.org]''' and '''[http://www.linuxfromscratch.org/blfs/view/development/chapter07/network.html Creating stable names for network interfaces on Linux]'''

<div class="centerBlock"><div class="noteMessage">'''Note:''' One can use the NST script: nstnetcfg to [[HowTo_Setup_A_Server_With_Multiple_Network_Interface_Adapters_Using:_%22nstnetcfg%22#Renaming_A_Network_Interface_Device | Rename A Network Interface Device]].
</div></div>

=== Overview ===
Starting with v197 systemd/udev will automatically assign predictable, stable network interface names for all local Ethernet, WLAN and WWAN interfaces. This is a departure from the traditional interface naming scheme ("eth0", "eth1", "wlan0", ...), but should fix real problems. The classic naming scheme for network interfaces applied by the kernel is to simply assign names beginning with "eth0", "eth1", ... to all interfaces as they are probed by the drivers. As the driver probing is generally not predictable for modern technology this means that as soon as multiple network interfaces are available the assignment of the names "eth0", "eth1" and so on is generally not fixed anymore and it might very well happen that "eth0" on one boot ends up being "eth1" on the next. This can have serious security implications, for example in firewall rules which are coded for certain naming schemes, and which are hence very sensitive to unpredictable changing names.

With systemd 197 we have added native support for a number of different naming policies into systemd/udevd proper and made a scheme similar to biosdevname's (but generally more powerful, and closer to kernel-internal device identification schemes) the default. The following different naming schemes for network interfaces are now supported by udev natively:

# Names incorporating Firmware/BIOS provided index numbers for on-board devices (example: eno1)
# Names incorporating Firmware/BIOS provided PCI Express hotplug slot index numbers (example: ens1)
# Names incorporating physical/geographical location of the connector of the hardware (example: enp2s0)
# Names incorporating the interfaces's MAC address (example: enx78e7d1ea46da)
# Classic, unpredictable kernel-native ethX naming (example: eth0)

By default, systemd v197 will now name interfaces following policy 1) if that information from the firmware is applicable and available, falling back to 2) if that information from the firmware is applicable and available, falling back to 3) if applicable, falling back to 5) in all other cases. Policy 4) is not used by default, but is available if the user chooses so.

This combined policy is only applied as last resort. That means, if the system has biosdevname installed, it will take precedence. If the user has added udev rules which change the name of the kernel devices these will take precedence too. Also, any distribution specific naming schemes generally take precedence.

The naming convention is documented in detail in a comment block for source code file: "'''[http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-net_id.c#n20 udev-builtin-net_id.c]'''". Please refer to document in case you are wondering how to decode the new interface names.

<div class="centerBlock"><div class="noteMessage">'''Note:''' If you see network names like '''p1p1''', '''p5p1''', '''p5p2''', etc... these are "'''biosdevnames'''". The udev rules file: "'''/usr/lib/udev/rules.d/71-biosdevname.rules'''" will process them. One can turn off  "'''biosdevnames'''" network interface name renaming using the following Kernel command line parameter:

 biosdevname=0

If you do this the naming convention described above will be used. 

To disable both the "'''biosdevnames'''" renaming and the "'''udev'''" renaming so that the original Kernel "'''ethx'''" (e.g., eth0) networking interface naming is used, which may be unpredictable, the use the following Kernel command line parameters:

 biosdevname=0 net.ifnames=0

</div></div>

=== Ways To Alter The Network Interface Names ===
You basically have four options:

# You disable the assignment of fixed names, so that the unpredictable kernel names are used again. For this, simply mask udev's rule file for the default policy: ''ln -s /dev/null /etc/udev/rules.d/80-net-name-slot.rules''
# You create your own manual naming scheme, for example by naming your interfaces "internet0", "dmz0" or "lan0". For that create your own udev rules file and set the NAME property for the devices. Make sure to order it before the default policy file, for example by naming it ''/etc/udev/rules.d/70-my-net-names.rules''
# You alter the default policy file, for picking a different naming scheme, for example for naming all interface names after their MAC address by default: ''cp /usr/lib/udev/rules.d/80-net-name-slot.rules /etc/udev/rules.d/80-net-name-slot.rules'', then edit the file there and change the lines as necessary.
# You pass the ''net.ifnames=0'' on the kernel command line (since v199)

==== Example: Want to Shorten the Network Interface Name: eno16777736 To eno1 ====
Here is an example on how to change the network interface name: "'''eno16777736'''" to "'''eno1'''".

Before Interface Name Change:
 [root@localhost network-scripts]# ip addr show
 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default 
     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
     inet 127.0.0.1/8 scope host lo
        valid_lft forever preferred_lft forever
     inet6 ::1/128 scope host 
        valid_lft forever preferred_lft forever
 2: eno16777736: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
     link/ether 00:0c:29:d2:af:fc brd ff:ff:ff:ff:ff:ff
     inet 10.222.222.116/24 brd 10.222.222.255 scope global dynamic eno1
        valid_lft 54243sec preferred_lft 54243sec
     inet6 fe80::20c:29ff:fed2:affc/64 scope link 
        valid_lft forever preferred_lft forever

We will use the '''Bus''' position as the key to identify the network interface name to change for the udev rule. Here is a way to find the '''Bus''' position:
 for dir in /sys/class/net/* ; do
   [ -e $dir/device ] && {
     basename $dir ; readlink -f $dir/device
   }
 done

Results:
 eno16777736
 /sys/devices/pci0000:00/0000:00:15.0/0000:03:00.0

Use the '''udevadm''' utility to list all udev environment variables for this network device (eno16777736):
 udevadm info /sys/class/net/eno16777736
 P: /devices/pci0000:00/0000:00:15.0/0000:03:00.0/net/eno16777736
 E: DEVPATH=/devices/pci0000:00/0000:00:15.0/0000:03:00.0/net/eno16777736
 E: ID_BUS=pci
 E: ID_MM_CANDIDATE=1
 E: ID_MODEL_FROM_DATABASE=VMXNET3 Ethernet Controller
 E: ID_MODEL_ID=0x07b0
 E: ID_NET_LABEL_ONBOARD=enEthernet0
 E: ID_NET_NAME_MAC=enx000c29d2affc
 E: ID_NET_NAME_ONBOARD=eno16777736
 E: ID_NET_NAME_PATH=enp3s0
 E: ID_NET_NAME_SLOT=ens160
 E: ID_OUI_FROM_DATABASE=VMware, Inc.
 E: ID_PCI_CLASS_FROM_DATABASE=Network controller
 E: ID_PCI_SUBCLASS_FROM_DATABASE=Ethernet controller
 E: ID_VENDOR_FROM_DATABASE=VMware
 E: ID_VENDOR_ID=0x15ad
 E: IFINDEX=2
 E: INTERFACE=eno16777736
 E: SUBSYSTEM=net
 E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/eno16777736
 E: TAGS=:systemd:
 E: USEC_INITIALIZED=30960

From the results we will now create a custom udev rules file: "'''/etc/udev/rules.d/79-my-net-name-slot.rules'''" to shorten the long network interface name to: "'''eno1'''":
 cat /etc/udev/rules.d/79-my-net-name-slot.rules;
 
 ACTION=="add", SUBSYSTEM=="net", ENV{ID_BUS}=="pci", KERNELS=="0000:03:00.0", NAME="eno1"

<div class="centerBlock"><div class="noteMessage">This is the udev rules file: "'''/etc/udev/rules.d/79-my-net-name-slot.rules'''" to shorten the long network interface name to: "'''eno1'''" using the '''MAC Address''':

 cat /etc/udev/rules.d/79-my-net-name-slot.rules;
 
 ACTION=="add", SUBSYSTEM=="net", ENV{ID_NET_NAME_MAC}=="enx000c29d2affc", NAME="eno1"

- OR -

 cat /etc/udev/rules.d/79-my-net-name-slot.rules;
 
 ACTION=="add", SUBSYSTEM=="net", ATTR{address}=="00:0c:29:d2:af:fc", NAME="eno1"

</div></div>

Files in "'''/etc/udev/rules.d/'''" are parsed in lexical order, and in some circumstances, the order in which rules are parsed is important. In general, you want your own rules to be parsed before the defaults. Therefore the udev rules file: "'''/etc/udev/rules.d/79-my-net-name-slot.rules'''" will be parsed before the default network udev rules file: "'''/usr/lib/udev/rules.d/80-net-name-slot.rules'''".

One can learn about writing udev rules files at the site: "'''[http://www.reactivated.net/writing_udev_rules.html reactivated.net - Writing udev Rules]'''".

One can now reboot the NST system for the interface name change to take effect:

After Interface Name Change:
 [root@localhost network-scripts]# ip addr show
 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default 
     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
     inet 127.0.0.1/8 scope host lo
        valid_lft forever preferred_lft forever
     inet6 ::1/128 scope host 
        valid_lft forever preferred_lft forever
 2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
     link/ether 00:0c:29:d2:af:fc brd ff:ff:ff:ff:ff:ff
     inet 10.222.222.116/24 brd 10.222.222.255 scope global dynamic eno1
        valid_lft 54243sec preferred_lft 54243sec
     inet6 fe80::20c:29ff:fed2:affc/64 scope link 
        valid_lft forever preferred_lft forever
'''
The '''udevadm''' utility now reveals the following for network device: "'''eno1'''"
 udevadm info /sys/class/net/eno1
 P: /devices/pci0000:00/0000:00:15.0/0000:03:00.0/net/eno1
 E: DEVPATH=/devices/pci0000:00/0000:00:15.0/0000:03:00.0/net/eno1
 E: ID_BUS=pci
 E: ID_MM_CANDIDATE=1
 E: ID_MODEL_FROM_DATABASE=VMXNET3 Ethernet Controller
 E: ID_MODEL_ID=0x07b0
 E: ID_NET_LABEL_ONBOARD=enEthernet0
 E: ID_NET_NAME_MAC=enx000c29d2affc
 E: ID_NET_NAME_ONBOARD=eno16777736
 E: ID_NET_NAME_PATH=enp3s0
 E: ID_NET_NAME_SLOT=ens160
 E: ID_OUI_FROM_DATABASE=VMware, Inc.
 E: ID_PCI_CLASS_FROM_DATABASE=Network controller
 E: ID_PCI_SUBCLASS_FROM_DATABASE=Ethernet controller
 E: ID_VENDOR_FROM_DATABASE=VMware
 E: ID_VENDOR_ID=0x15ad
 E: IFINDEX=2
 E: INTERFACE=eno1
 E: SUBSYSTEM=net
 E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/eno1
 E: TAGS=:systemd:
 E: USEC_INITIALIZED=30960

==== HowTo Debug A udev Rules File ====
One can use the "''udevadm test <devpath>''" command to verify, detect any errors and debug your udev rules file. The "''<devpath>''" is the "'''/sys'''" path of the device to query. Below is an example for our network interface device: "'''eno1'''"

 udevadm test /sys/class/net/eno1
 calling: test
 version 208
 This program is for debugging only, it does not run any program
 specified by a RUN key. It may show incorrect results, because
 some values may be different, or not available at a simulation run.
 
 === trie on-disk ===
 tool version:          208
 file size:         5913667 bytes
 header size             80 bytes
 strings            1299963 bytes
 nodes              4613624 bytes
 load module index
 read rules file: /usr/lib/udev/rules.d/10-dm.rules
 read rules file: /usr/lib/udev/rules.d/11-dm-lvm.rules
 read rules file: /usr/lib/udev/rules.d/13-dm-disk.rules
 read rules file: /usr/lib/udev/rules.d/40-libgphoto2.rules
 IMPORT found builtin 'usb_id --export %%p', replacing /usr/lib/udev/rules.d/40-libgphoto2.rules:11
 read rules file: /usr/lib/udev/rules.d/40-usb-media-players.rules
 read rules file: /usr/lib/udev/rules.d/40-usb_modeswitch.rules
 read rules file: /usr/lib/udev/rules.d/42-usb-hid-pm.rules
 read rules file: /usr/lib/udev/rules.d/50-udev-default.rules
 read rules file: /usr/lib/udev/rules.d/56-hpmud.rules
 read rules file: /usr/lib/udev/rules.d/60-cdrom_id.rules
 read rules file: /usr/lib/udev/rules.d/60-drm.rules
 read rules file: /usr/lib/udev/rules.d/60-fprint-autosuspend.rules
 read rules file: /usr/lib/udev/rules.d/60-keyboard.rules
 read rules file: /usr/lib/udev/rules.d/60-net.rules
 read rules file: /usr/lib/udev/rules.d/60-pcmcia.rules
 read rules file: /usr/lib/udev/rules.d/60-persistent-alsa.rules
 read rules file: /usr/lib/udev/rules.d/60-persistent-input.rules
 read rules file: /usr/lib/udev/rules.d/60-persistent-serial.rules
 read rules file: /usr/lib/udev/rules.d/60-persistent-storage-tape.rules
 read rules file: /usr/lib/udev/rules.d/60-persistent-storage.rules
 read rules file: /usr/lib/udev/rules.d/60-persistent-v4l.rules
 read rules file: /usr/lib/udev/rules.d/60-raw.rules
 read rules file: /usr/lib/udev/rules.d/61-accelerometer.rules
 read rules file: /usr/lib/udev/rules.d/61-gnome-bluetooth-rfkill.rules
 read rules file: /usr/lib/udev/rules.d/62-multipath.rules
 read rules file: /usr/lib/udev/rules.d/63-md-raid-arrays.rules
 read rules file: /usr/lib/udev/rules.d/64-btrfs.rules
 read rules file: /usr/lib/udev/rules.d/64-md-raid-assembly.rules
 read rules file: /usr/lib/udev/rules.d/65-libwacom.rules
 read rules file: /usr/lib/udev/rules.d/65-md-incremental.rules
 read rules file: /usr/lib/udev/rules.d/65-sane-backends.rules
 read rules file: /usr/lib/udev/rules.d/69-cd-sensors.rules
 read rules file: /usr/lib/udev/rules.d/69-dm-lvm-metad.rules
 read rules file: /usr/lib/udev/rules.d/69-libmtp.rules
 read rules file: /usr/lib/udev/rules.d/69-xorg-vmmouse.rules
 read rules file: /usr/lib/udev/rules.d/70-power-switch.rules
 read rules file: /usr/lib/udev/rules.d/70-printers.rules
 read rules file: /usr/lib/udev/rules.d/70-spice-vdagentd.rules
 read rules file: /usr/lib/udev/rules.d/70-touchpad-quirks.rules
 read rules file: /usr/lib/udev/rules.d/70-uaccess.rules
 read rules file: /usr/lib/udev/rules.d/70-wacom.rules
 read rules file: /usr/lib/udev/rules.d/71-biosdevname.rules
 read rules file: /usr/lib/udev/rules.d/71-seat.rules
 read rules file: /usr/lib/udev/rules.d/73-seat-late.rules
 read rules file: /usr/lib/udev/rules.d/75-net-description.rules
 read rules file: /usr/lib/udev/rules.d/75-probe_mtd.rules
 read rules file: /usr/lib/udev/rules.d/75-tty-description.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-ericsson-mbm.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-huawei-net-port-types.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-longcheer-port-types.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-nokia-port-types.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-pcmcia-device-blacklist.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-platform-serial-whitelist.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-simtech-port-types.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-telit-port-types.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-usb-device-blacklist.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-usb-serial-adapters-greylist.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-x22x-port-types.rules
 read rules file: /usr/lib/udev/rules.d/77-mm-zte-port-types.rules
 read rules file: /usr/lib/udev/rules.d/77-nm-olpc-mesh.rules
 read rules file: /usr/lib/udev/rules.d/78-sound-card.rules
 '''''read rules file: /etc/udev/rules.d/79-my-net-name-slot.rules'''''
 read rules file: /usr/lib/udev/rules.d/80-drivers.rules
 read rules file: /usr/lib/udev/rules.d/80-mm-candidate.rules
 read rules file: /usr/lib/udev/rules.d/80-net-name-slot.rules
 read rules file: /usr/lib/udev/rules.d/80-udisks2.rules
 read rules file: /usr/lib/udev/rules.d/85-regulatory.rules
 read rules file: /usr/lib/udev/rules.d/85-usbmuxd.rules
 read rules file: /usr/lib/udev/rules.d/90-alsa-restore.rules
 read rules file: /usr/lib/udev/rules.d/90-alsa-tools-firmware.rules
 read rules file: /usr/lib/udev/rules.d/90-libgpod.rules
 read rules file: /usr/lib/udev/rules.d/90-pulseaudio.rules
 read rules file: /usr/lib/udev/rules.d/91-drm-modeset.rules
 read rules file: /usr/lib/udev/rules.d/95-cd-devices.rules
 read rules file: /usr/lib/udev/rules.d/95-dm-notify.rules
 read rules file: /usr/lib/udev/rules.d/95-udev-late.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-battery-recall-dell.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-battery-recall-fujitsu.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-battery-recall-gateway.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-battery-recall-ibm.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-battery-recall-lenovo.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-battery-recall-toshiba.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-csr.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-hid.rules
 read rules file: /usr/lib/udev/rules.d/95-upower-wup.rules
 read rules file: /etc/udev/rules.d/98-kexec.rules
 read rules file: /usr/lib/udev/rules.d/99-qemu-guest-agent.rules
 read rules file: /usr/lib/udev/rules.d/99-systemd.rules
 rules contain 393216 bytes tokens (32768 * 12 bytes), 37195 bytes strings
 30305 strings (254465 bytes), 26909 de-duplicated (220667 bytes), 3397 trie nodes used
 PROGRAM '/lib/udev/rename_device' /usr/lib/udev/rules.d/60-net.rules:1
 starting '/lib/udev/rename_device'
 '/lib/udev/rename_device' [2664] exit with return code 0
 PROGRAM '/sbin/biosdevname --policy physical -i eno1' /usr/lib/udev/rules.d/71-biosdevname.rules:22
 starting '/sbin/biosdevname --policy physical -i eno1'
 '/sbin/biosdevname --policy physical -i eno1' [2665] exit with return code 4
 IMPORT builtin 'net_id' /usr/lib/udev/rules.d/75-net-description.rules:6
 IMPORT builtin 'hwdb' /usr/lib/udev/rules.d/75-net-description.rules:12
 '''''NAME 'eno1' /etc/udev/rules.d/79-my-net-name-slot.rules:2'''''
 RUN '/usr/lib/systemd/systemd-sysctl --prefix=/proc/sys/net/ipv4/conf/$name --prefix=/proc/sys/net/ipv4/neigh/$name --prefix=/proc/sys/net/ipv6/conf/$name --    prefix=/proc/sys/net/ipv6/neigh/$name' /usr/lib/udev/rules.d/99-systemd.rules:52
 ACTION=add
 DEVPATH=/devices/pci0000:00/0000:00:15.0/0000:03:00.0/net/eno1
 ID_BUS=pci
 ID_MM_CANDIDATE=1
 ID_MODEL_FROM_DATABASE=VMXNET3 Ethernet Controller
 ID_MODEL_ID=0x07b0
 ID_NET_LABEL_ONBOARD=enEthernet0
 ID_NET_NAME_MAC=enx000c29d2affc
 ID_NET_NAME_ONBOARD=eno16777984
 ID_NET_NAME_PATH=enp3s0
 ID_NET_NAME_SLOT=ens160
 ID_OUI_FROM_DATABASE=VMware, Inc.
 ID_PCI_CLASS_FROM_DATABASE=Network controller
 ID_PCI_SUBCLASS_FROM_DATABASE=Ethernet controller
 ID_VENDOR_FROM_DATABASE=VMware
 ID_VENDOR_ID=0x15ad
 IFINDEX=2
 INTERFACE=eno1
 SUBSYSTEM=net
 SYSTEMD_ALIAS=/sys/subsystem/net/devices/eno1
 TAGS=:systemd:
 USEC_INITIALIZED=30960
 run: '/usr/lib/systemd/systemd-sysctl --prefix=/proc/sys/net/ipv4/conf/eno1 --prefix=/proc/sys/net/ipv4/neigh/eno1 --prefix=/proc/sys/net/ipv6/conf/eno1 --prefix=/proc/sys/net/ipv6/neigh/eno1'
 unload module index

This command will verify the correct syntax for each udev rules file and also show the order in which each rules file is processed. If a syntax error had occurred, it would be shown for the offending file. Most likely any errors that occurred would be associated with our custom udev rules file.

The custom udev rules file: "'''/etc/udev/rules.d/79-my-net-name-slot.rules'''" is in '''''Italic Bold''''' text above and is also shown as the udev rules file that was responsible for the network interface rename from '''eth0''' to '''eno1'''.

From '''dmesg''' we see when the actual udev rule was used to rename the network interface during the system boot process:

 [    4.526042] systemd-udevd[419]: renamed network interface eth0 to eno1