[SOLVED] hostname changes based on network connection

BryanFRitt · 02-04-2018, 10:20 AM

[Debian 9.x Stable Stretch, KDE]

I tried to change or keep my 'hostname' to 'PC', but it doesn't stick.

Code:

echo PC | sudo tee /etc/hostname
sudo hostname PC
sudo hostnamectl set-hostname PC

But it changes when I switch how I connect to the network. (Wi-Fi, Ethernet, ...)

How can I keep the hostname the same no matter what the network connection? or should I not do this?

inside of my /etc/hosts file

Quote:

127.0.0.1 localhost

::1 ip6-localhost ip6-loopback
::1 localhost6.localdomain6 localhost6
::1 localhost ip6-localhost ip6-loopback
::1 localhost
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

127.0.0.1 PC

ferrari · 02-04-2018, 03:29 PM

Check how the DHCP client is configured. (For example, the 'send host-name' option in dhclient.conf)

BryanFRitt · 02-04-2018, 04:05 PM

Quote:

Originally Posted by ferrari

Check how the DHCP client is configured. (For example, the 'send host-name' option in dhclient.conf)

I found a /etc/dhcp/dhclient.conf file. It had "send host-name = gethostname();" in it.

Quote:

option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;

send host-name = gethostname();
request subnet-mask, broadcast-address, time-offset, routers,
domain-name, domain-name-servers, domain-search, host-name,
dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers,
netbios-name-servers, netbios-scope, interface-mtu,
rfc3442-classless-static-routes, ntp-servers;

The rest was commented out.

What does this statement do?, and how to fix things?

Should I change it to something like "send host-name = 'PC';"?
Just tried that and it didn't fix anything.

BryanFRitt · 02-04-2018, 04:18 PM

I can change the hostname to 'PC' temporarily with those commands, but after 2nd reboot with the network device connected, the hostname isn't kept, and the hostname changes whenever I disconnect one network connection and activate another one.

ferrari · 02-04-2018, 04:40 PM

Are you using NetworkManager to manage your connections?

First you need to establish which DHCP client is in use.

The following command might help with that

Code:

ps -A|grep dh

ferrari · 02-04-2018, 04:51 PM

Quote:

I found a /etc/dhcp/dhclient.conf file. It had "send host-name = gethostname();" in it.

Quote:
option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;

send host-name = gethostname();
request subnet-mask, broadcast-address, time-offset, routers,
domain-name, domain-name-servers, domain-search, host-name,
dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers,
netbios-name-servers, netbios-scope, interface-mtu,
rfc3442-classless-static-routes, ntp-servers;
The rest was commented out.

What does this statement do?, and how to fix things?

If dhclient really is use, that should be sufficient, and it can also be hard set as you mentioned. However, you need to answer the question about whether you're using NetworkManager.

BryanFRitt · 02-04-2018, 05:00 PM

Quote:

Originally Posted by ferrari

Are you using NetworkManager to manage your connections?

First you need to establish which DHCP client is in use.

The following command might help with that

Code:

ps -A|grep dh

results in

Quote:

5139 ? 00:00:00 dhclient

BryanFRitt · 02-04-2018, 05:20 PM

Quote:

Originally Posted by ferrari

If dhclient really is use, that should be sufficient, and it can also be hard set as you mentioned. However, you need to answer the question about whether you're using NetworkManager.

I tried the "hard set" method, and it didn't work. Still goes by network device name.

If I use those `sudo hostname PC` commands it'll keep the hostname on the first reboot, but on second, etc... the hostname will go by the network device name.(not sure what to call it.) I can tell this by the KDE login screen's message "Welcome to ...". [UPDATE: on this screen I can choose restart X server, and the hostname shown will change to one based on network device]

It is possible I may have (in/un)installed/changed something that effects this when dealing with NVidia video card drivers, and/or OS recovery. ?Don't know?

ferrari · 02-04-2018, 05:21 PM

Ok, and are you using NetworkManager or a connection defined in /etc/network/interfaces?

BryanFRitt · 02-04-2018, 05:41 PM

Quote:

Originally Posted by ferrari

Ok, and are you using NetworkManager or a connection defined in /etc/network/interfaces?

I haven't explicitly set any network manager that I know of.

Code:

cat /etc/network/interfaces | egrep -v '#|^$'

Quote:

source /etc/network/interfaces.d/*
auto lo
iface lo inet loopback
dns-nameservers 208.67.220.123 208.67.222.123

The dns-nameservers are for OpenDNS FamilyShield

Code:

ls -aR /etc/network/interfaces*

Quote:

/etc/network/interfaces

/etc/network/interfaces.d:
. ..

ferrari · 02-04-2018, 05:50 PM

Well, to be connected to the internet you're likely to be using one or the other. Based on the the last post, I assume NM is running

Code:

ps -A|grep -i net

https://manpages.debian.org/testing/...conf.5.en.html

Quote:

hostname-mode
Set the management mode of the hostname. This parameter will affect only the transient hostname. If a valid static hostname is set, NetworkManager will skip the update of the hostname despite the value of this option. An hostname empty or equal to 'localhost', 'localhost6', 'localhost.localdomain' or 'localhost6.localdomain' is considered invalid.

default: NetworkManager will update the hostname with the one provided via DHCP on the main connection (the one with a default route). If not present, the hostname will be updated to the last one set outside NetworkManager. If it is not valid, NetworkManager will try to recover the hostname from the reverse lookup of the IP address of the main connection. If this fails too, the hostname will be set to 'localhost.localdomain'.

dhcp: NetworkManager will update the transient hostname only with information coming from DHCP. No fallback nor reverse lookup will be performed, but when the dhcp connection providing the hostname is deactivated, the hostname is reset to the last hostname set outside NetworkManager or 'localhost' if none valid is there.

none: NetworkManager will not manage the transient hostname and will never set it.

BryanFRitt · 02-04-2018, 06:26 PM

Code:

ps -A|grep -i net

Quote:

56 ? 00:00:00 netns
964 ? 00:00:00 inetd
1012 ? 00:00:06 NetworkManager

ferrari · 02-04-2018, 07:03 PM

Ok, that confirms NetworkManager.

Hmmm...the Debian Stretch NM reference suggests NM honours the name set in /etc/hostname
https://manpages.debian.org/stretch/...conf.5.en.html

By default dhclient is used by NetworkManager, so that is where the hostname is pushed from.

Quote:

dhcp
This key sets up what DHCP client NetworkManager will use. Allowed values are dhclient, dhcpcd, and internal. The dhclient and dhcpcd options require the indicated clients to be installed. The internal option uses a built-in DHCP client which is not currently as featureful as the external clients.

If this key is missing, it defaults to dhclient. It the chosen plugin is not available, clients are looked for in this order: dhclient, dhcpcd, internal.

ferrari · 02-04-2018, 07:18 PM

Returning to the dhclient.conf config you posted in post #3

Code:

request subnet-mask, broadcast-address, time-offset, routers,
domain-name, domain-name-servers, domain-search, host-name,
dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers,
netbios-name-servers, netbios-scope, interface-mtu,
rfc3442-classless-static-routes, ntp-servers;

Remove the 'host-name' entry from the request, and check behaviour after restarting NetworkManager or perhaps reboot.

This might be useful to you...
https://support.cumulusnetworks.com/...stname-Option-

BryanFRitt · 02-04-2018, 08:04 PM

Thought this fixed it for a while, hostname is staying 'PC' and not changing based on network interface, but...
Now deja-dup is saying computer name is localhost instead of 'PC' or the network interface name.

Do I need to put "127.0.0.1 PC" before "127.0.0.1 localhost" in /etc/hosts ? or change another file?

What I did (not sure why I looked this up...)

Code:

apt-file search /etc/init.d/hostname.sh

Quote:

initscripts: /etc/init.d/hostname.sh

Code:

sudo apt-get purge initscripts

Code:

sudo hostname PC
sudo hostnamectl set-hostname PC

[UPDATE]forgot to say I reinstalled initscripts back later[/UPDATE]
---
Haven't tried this yet

Quote:

Remove the 'host-name' entry from the request, and check behaviour after restarting NetworkManager or perhaps reboot.