How to set the domain name on GNU/Linux?
I want to change my domain name. I can use the domainname command, but is there a way to make it permanent across reboots? I think it can be configured in /etc/resolv.conf but this file is generally generated and I don’t know exactly the difference between search and domain directives. And at what time exactly the information there is passed to the domainname program to set the domain name?
Do you have any ideas on that?
I’d like to be mostly compatible across distributions. So if if anyone has pointers on the different distributions flavours, I’d gladly accept them.
Every distribution does this differently. Which ones are you interested in? And did you read their documentation?
Mostly RedHat and Debian flavours. And I couldn’t find relevant information in the documentation. But perhaps I haven’t looked hard enough, I admit I don’t know exactly where in the documentation it could be (or even if it is in the docs).
That’s fair. In Red Hat’s documentation, it’s buried in an appendix. While in Debian’s it’s not buried in an appendix, but it is confusing.
@Michael This link on the debian mailing list is mostly useful, especially So to finally answer your question, you configure your FQDN wherever you want names resovled. If you want it in files on the box itself, then it goes in /etc/hosts. If you run your own name server like I do (I run dnsmasq for simplicity) then you only have to record the information in
On red hat 7 and derived systems you should use hostnamectl to set up the hostname. cyberciti.biz/faq/rhel-redhat-centos-7-change-hostname-command/…
3 Answers 3
Set FQDN
I’m using Debian 7 and this is what worked for me; thanks to Fernando Ribeiro.
server # here's where you put the server's host name activate hostname
add domain name and address to the server
192.168.1.2 server.domain server VERIFY
> hostname --short server > hostname --domain domain > hostname --fqdn server.domain > hostname --ip-address 192.168.1.2 after changing server name in /etc/hostname you might not be able to edit /etc/hosts . In this case you have to use xauth add as stated in this answer stackoverflow.com/questions/20611783/…
When you use redhat-base systems, linux uses /etc/sysconfig/network file and you should set variable HOSTNAME to FQDN , when you use FQDN , linux itself determines domain name.
But when you use debian-base systems, you should fill /etc/hostname file with FQDN :
NOTE: if you want to set domain name be sure set FQDN (Fully Qualyfied Domain Name)
When you set, hostname -d shows you the domain name .
Thank you, but I was under the impression that these files should only contain the hostname without the domain part. If I do what you suggest, hostname will return the fqdn directly (no difference between hostname and hostname -f ).
oh by the way, i forget to say you should set hostname by hand hostname web.mydomain.com after configure your files. because when you configure your file memory can’t apply changes.(if it was useful, don’t forget useful flag)
man hostname , being cited from its end to beginning
FILES /etc/hostname Historically this file was supposed to only contain the hostname and not the full canonical FQDN. Nowadays most software is able to cope with a full FQDN here. This file is read at boot time by the system initialization scripts to set the hostname. /etc/hosts Usually, this is where one sets the domain name by aliasing the host name to the FQDN. THE FQDN The FQDN (Fully Qualified Domain Name) of the system is the name that the resolver(3) returns for the host name, such as, ursula.example.com. It is usually the hostname followed by the DNS domain name (the part after the first dot). You can check the FQDN using hostname --fqdn or the domain name using dnsdomainname. You cannot change the FQDN with hostname or dnsdomainname. The recommended method of setting the FQDN is to make the hostname be an alias for the fully qualified name using /etc/hosts, DNS, or NIS. For example, if the hostname was "ursula", one might have a line in /etc/hosts which reads 127.0.1.1 ursula.example.com ursula Technically: The FQDN is the name getaddrinfo(3) returns for the host name returned by gethostname(2). The DNS domain name is the part after the first dot. Therefore it depends on the configuration of the resolver (usually in /etc/host.conf) how you can change it. Usually the hosts file is parsed before DNS or NIS, so it is most common to change the FQDN in /etc/hosts. If a machine has multiple network interfaces/addresses or is used in a mobile environment, then it may either have multiple FQDNs/domain names or none at all. Therefore avoid using hostname --fqdn, hostname --domain and dnsdomainname. hostname --ip-address is subject to the same limitations so it should be avoided as well. I’d say it does describe the whole thing thoroughly.
How to correctly set hostname and domain name?
I am also renting a domain name, let’s name it domain.org . What I would like to do would be to rename my server as server1.domain.org .
This means configuring my hostname as server1 and my domain name as domain.org .
How can I do it correctly?
Indeed, the manpage for hostname is not clear. To me at least:
- When called with one argument or with the —file option, the commands set the host name or the NIS/YP domain name. hostname uses the sethostname(2) function, while all of the three domainname, ypdomainname and nisdomainname use setdomainname(2). Note, that this is effective only until the next reboot. Edit /etc/hostname for permanent change.
- You cannot change the FQDN with hostname or dnsdomainname.
So it seems that editing /etc/hostname is not enough? Because if it really changed the hostname, it would have changed the FQDN. There’s also a trick I read to change the hostname with the command sysctl kernel.hostname=server1 , but nothing says whether this is the correct way or an ugly trick.
- What is the correct way to set the hostname?
- What is the correct way to set the domain name?
5 Answers 5
- You’ll want to edit /etc/hostname with your new hostname.
- Then, run sudo hostname $(cat /etc/hostname) .
Setting your domain, assuming you have a resolvconf binary:
- In /etc/resolvconf/resolv.conf.d/head , you’ll add then line domain your.domain.name (not your FQDN, just the domain name).
- Then, run sudo resolvconf -u to update your /etc/resolv.conf (alternatively, just reproduce the previous change into your /etc/resolv.conf ).
If you do not have resolvconf , just edit /etc/resolv.conf , adding the domain your.domain.name line.
Finally, update your /etc/hosts file. There should be at least one line starting with one of your IP (loopback or not), your FQDN and your hostname. grepping out ipv6 addresses, your hosts file could look like this:
127.0.0.1 localhost 1.2.3.4 service.domain.com service In response to hostnamectl suggestions piling up in comments: it is not mandatory, nor exhaustive.
It can be used as a replacement for step 1 & 2, IF you OS ships with systemd. Whereas the steps given above are valid regardless of systemd being present (pclinuxos, devuan, . ).
Both those conf files say DO NOT EDIT THIS FILE BY HAND — YOUR CHANGES WILL BE OVERWRITTEN on my server (same version).
Don’t be fooled by the fact that the «DO NOT EDIT» warning appears in /etc/resolvconf/resolv.conf.d/head . Everything in the head file is prepended to the resulting /etc/resolv.conf output file, so that’s why the warning is in there, so that it shows up in the final result. Threw me for a loop at first.
This doesn’t seem to apply to 18.04 LTS — there’s no such file /etc/resolvconf/resolv.conf.d/head and there’s no such utility resolvconf .
Note also that if you use AWS you’ll also need to preserve the hostname after reboots — sudo nano /etc/cloud/cloud.cfg update preserve_hostname: true (default is false ).
127.0.0.1 hostname.domain.com hostname localhost MUST HAVE SINGLE HOSTNAME after FQDN in /etc/hosts file. Works fine on Ubuntu 18.04.1 and all other versions. On EC2 and elsewhere.
Didn’t mess with resolve file or anything else.
That shows hostname in shell and then has the FQDN when you need it.
@MikeCiffone Technically, hostname should not contain the domain name — i.e. should not be FQDN. Many deployments do it, but it should not be done that way. Note that in-kernel hostname under Linux after 1.0 is restricted to 64 characters (see man 2 sethostname ) because that’s the value of HOST_NAME_MAX . (Until 1.0 it was mere 8 bytes.)
@bfontaine You don’t have to care about any of the reasons I’ll state — most of my hosts were configured with hostname=fqdn most of the time, and they worked. One reason is that your FQDN, not shortname, is then limited to 63ch ( HOST_NAME_MAX ). Another is that molly-guard will require you to type fqdn, not the shortname. Another is that hostname CLI prints out the full FQDN, not just hostname -f . Another is that some software might print out FQDN in place of shortname, or append the domain a second time to the FQDN (i.e. foo.example.org.example.org instead of foo.example.org ).
You can, of course, dismiss all of these as hypotheticals — but I feel correctness of having the hostname contain just, well, the hostname is more correct and professional.
Instructions written against Ubuntu 18.04.3 LTS (bionic)
sudo hostnamectl set-hostname server1 Check result by running hostnamectl :
root@www:/# hostnamectl Static hostname: server1 Change the domain via new network manager, Netplan, by editing /etc/netplan/01-netcfg.yaml and changing the search parameter:
sudoedit /etc/netplan/01-netcfg.yaml # This file describes the network interfaces available on your system # For more information, see netplan(5). network: version: 2 renderer: networkd ethernets: eth0: dhcp4: yes nameservers: search: [ domain.org ] Test changes by logging in a second time, and running sudo netplan try in one of the sessions and checking settings in the other:
# netplan try Do you want to keep these settings? Press ENTER before the timeout to accept the new configuration Changes will revert in 97 seconds Configuration accepted. # systemd-resolve --status . Link 2 (eth0) Current Scopes: DNS LLMNR setting: yes MulticastDNS setting: no DNSSEC setting: no DNSSEC supported: no DNS Servers: 8.8.8.8 8.8.4.4 DNS Domain: domain.org # cat /etc/resolv.conf . nameserver 127.0.0.53 options edns0 search domain.org # hostname -f server1.domain.org It all is well, press ENTER at the sudo netplan try prompt to make things permanent.
[…] You cannot change the FQDN with hostname or dnsdomainname. The recommended method of setting the FQDN is to make the hostname be an alias for the fully qualified name using /etc/hosts, DNS, or NIS. For example, if the hostname was "ursula", one might have a line in /etc/hosts which reads 127.0.1.1 ursula.example.com ursula Technically: The FQDN is the name getaddrinfo(3) returns for the host name returned by gethostname(2). The DNS domain name is the part after the first dot. Therefore it depends on the configuration of the resolver (usually in /etc/host.conf) how you can change it. Usually the hosts file is parsed before DNS or NIS, so it is most common to change the FQDN in /etc/hosts. If a machine has multiple network interfaces/addresses or is used in a mobile environment, then it may either have multiple FQDNs/domain names or none at all. Therefore avoid using hostname --fqdn, hostname --domain and dnsdomainname. hostname --ip- address is subject to the same limitations so it should be avoided as well. […] This was kindly pointed out by poige in another thread and is exactly what Lutz proposed here.
You should not put your fqdn into /etc/hostname .
I tried to change my domain entry from myhome.local to myhome.lan I had to edit the /etc/hosts file and the /etc/network/interfaces file. My /etc/hosts file now looks like:
127.0.0.1 localhost 192.168.3.2 server.myhome.lan server and my /etc/network/interfaces file now looks like:
# This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). source /etc/network/interfaces.d/* # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto enp2s0 iface enp2s0 inet static address 192.168.3.2 netmask 255.255.255.0 network 192.168.3.0 broadcast 192.168.3.255 gateway 192.168.3.1 # dns-* options are implemented by the resolvconf package, if installed dns-nameservers 192.168.3.1 dns-search myhome.lan