Arch Linux

wangchong

Member

Registered: 2013-06-25

Posts: 76

Understanding the behavior of NetworkManager

I use gnome with NetworkManager in Arch linux. However, I found NetworkManager rather puzzling.

I have a network interface with the name 'enp3s0', and I edited the connection with nmtui, changing ipv6 from ignore to automatic.

However, when I restarted NetworkManager, another enp3s0 connection was set up and connected with ipv6 in ignore state.

I don't understand the situation here and I want to know when will NetworkManager set up a new connection automatically (even if I don't want to)?

CyberLard

Member

Registered: 2015-08-07

Posts: 10

Re: Understanding the behavior of NetworkManager

What does /etc/NetworkManager/system-connections/<connection name> contain?

What DHCP client is it using? I'd imagine dhclient, but check with:

# journalctl -b | egrep "dhc"

wangchong

Member

Registered: 2013-06-25

Posts: 76

Re: Understanding the behavior of NetworkManager

[wangc@wangc-work ~]$ ls  /etc/NetworkManager/system-connections/
wired
[wangc@wangc-work ~]$ sudo journalctl -b -r | egrep "dhc"
Aug 18 19:44:10 wangc-work dhclient[4493]: bound to 166.111.26.145 -- renewal in 1667 seconds.
Aug 18 19:44:10 wangc-work dhclient[4493]: DHCPACK from 166.111.26.1
Aug 18 19:44:09 wangc-work dhclient[4493]: DHCPOFFER from 166.111.26.1
Aug 18 19:44:09 wangc-work dhclient[4493]: DHCPREQUEST on enp3s0 to 255.255.255.255 port 67
Aug 18 19:44:08 wangc-work dhclient[4493]: DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 20
Aug 18 19:44:00 wangc-work dhclient[4493]: DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 8
Aug 18 19:44:00 wangc-work NetworkManager[4489]: <info>  dhclient started with pid 4493
Aug 18 19:43:52 wangc-work dhclient[4437]: bound to 166.111.27.63 -- renewal in 1537 seconds.
Aug 18 19:43:52 wangc-work dhclient[4437]: DHCPACK from 166.111.26.1
Aug 18 19:43:52 wangc-work dhclient[4437]: DHCPOFFER from 166.111.26.1
Aug 18 19:43:52 wangc-work dhclient[4437]: DHCPREQUEST on enp3s0 to 255.255.255.255 port 67
Aug 18 19:43:52 wangc-work dhclient[4437]: DHCPDISCOVER on enp3s0 to 255.255.255.255 port 67 interval 5
Aug 18 19:43:52 wangc-work NetworkManager[4338]: <info>  dhclient started with pid 4437
Aug 18 19:43:03 wangc-work dhclient[4357]: bound to 166.111.27.63 -- renewal in 1479 seconds.
Aug 18 19:43:03 wangc-work dhclient[4357]: DHCPACK from 166.111.26.1
Aug 18 19:43:03 wangc-work dhclient[4357]: DHCPOFFER from 166.111.26.1

Yeah, it's using dhclient.
There is only one item 'wired' in that directory, which is what I configured in nmtui. However, nmtui shows I am connected to another connection 'enp3s0'.

Last edited by wangchong (2015-08-18 11:48:57)

Raynman

Member

Registered: 2011-10-22

Posts: 1,539

Re: Understanding the behavior of NetworkManager

I think I've seen something like that once (second connection with some generic name) when something else already set up the network before NM was started. Are you sure NetworkManager.service is the only network service you have enabled?

wangchong

Member

Registered: 2013-06-25

Posts: 76

Re: Understanding the behavior of NetworkManager

Yeah, I am sure I shut down dhcpcd before turn on Networkmanager. Is there any other services I have to pay attention to?

wangchong

Member

Registered: 2013-06-25

Posts: 76

Re: Understanding the behavior of NetworkManager

It seems when NetworkManager cannot fulfilll my request (Here I request it to get an ipv6 addr which it can't), it will set up a new connection. Is it right?

Last edited by wangchong (2015-08-18 12:42:56)

CyberLard

Member

Registered: 2015-08-07

Posts: 10

Re: Understanding the behavior of NetworkManager

Just to be clear, I do not use NetworkManager, so I'm basing this entirely off of quick Google-fu and years of using Linux.

When you save a connection, it is supposed to be added as a file to  /etc/NetworkManager/system-connections/

It is obviously not doing that, so it could be a few different things. My guess is that it is either a permissions problem or that it is currently unsupported with nmtui (see the note at the bottom re: Wi-Fi connections using WPA Enterprise, or Ethernet connections using 802.1X here: https://access.redhat.com/documentation … nmtui.html )

My suggestion would be to try using the standard GUI or nmcli to add the connection first. If that doesn't work, have a look at https://wiki.archlinux.org/index.php/Ne … ermissions

wangchong

Member

Registered: 2013-06-25

Posts: 76

Re: Understanding the behavior of NetworkManager

Cyber, a file called wired is added to /etc/NetworkManager/system-connections/. That is what I configured, so there's no problem in this sense.

CyberLard

Member

Registered: 2015-08-07

Posts: 10

Re: Understanding the behavior of NetworkManager

Oh. I missed that that was what you configured. What are its contents?