How to generate a uuid for eth0 from command line ?

5883 · 01-16-2014, 06:16 PM

hi, if you have NetworkManager, you can check the uuid value in its config files.

Now how does it come up with this uuid in the first place ?
i need to manually generate uuid for eth0.

The real question is, how to change dhcp to static ip from command line if you are using ubuntu 12.04 ?

Thanks !

berndbausch · 01-17-2014, 01:40 AM

Quote:

Originally Posted by 5883

The real question is, how to change dhcp to static ip from command line if you are using ubuntu 12.04 ?

On a non-Ubuntu Debian system (raspbian, to be precise), the file /etc/network/interfaces contains the network interfaces descriptions. On my system:

Code:

iface eth0 inet static
        address 192.168.1.16
        netmask 255.255.255.0
        gateway 192.168.1.1

For more info, try man interfaces.

I can't answer your question about the UUID though.

anon237 · 01-17-2014, 03:41 AM

Quote:

Originally Posted by 5883

hi, if you have NetworkManager, you can check the uuid value in its config files.

Now how does it come up with this uuid in the first place ?
i need to manually generate uuid for eth0.

Network interfaces do not have an UUID, they do have an unique hardware address (HWaddr).

You don't tell us why you need to generate this value. Generally you don't need to provide one, the network interface already has a unique hw address.

If you do want to create one: The general layout is 6 two digit fields separated by a colon (a1:b2:c3:d4:e5:f6), each digit is made up of a number from 0 to F (hexadecimal). Any random combination will do as long as it is not the same as other (virtual) network interfaces on your box.

Here's a one-liner that will generate a random hwaddr:

Code:

openssl rand -hex 6 | sed 's/\(..\)\(..\)\(..\)\(..\)\(..\)\(..\)/\1:\2:\3:\4:\5:\6/'

ericson007 · 01-17-2014, 04:06 AM

Network manager doesn't create the uuid. The system does.

Never tried with nics, but with hdd you can use blkid to get the uuid.

I still am not sure on a small system why it is useful, but on a cluster that is centrally managed containing 300 network cards, the uuid can help out by identifying the actual component rather than eth0 since hundreds of systems would contain eth0

You can also use uuid to mount your partitions etc.

anon237 · 01-17-2014, 04:48 AM

I've never come across a uuid entry for network interfaces, but some research shows that it can be present.

Anyway: If you want/need to generate a random UUID: Have a look at the uuidgen command (uuidgen(1) - Linux man page)

ericson007 · 01-17-2014, 06:15 AM

Uuid is generated as standard on rhel and derivatives. I honestly don't bother with them, if they are there after install, i leave them, but if i manually do fstab entries or nic configs, i don't bother since on a single system i find they make it more difficult to understand which component is involved.