Query and change the system hostname.
Display operating system.
$ lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 10 (buster) Release: 10 Codename: buster
Display hostname settings.
$ hostnamectl
Static hostname: debian
Icon name: computer-vm
Chassis: vm
Machine ID: 5b1a78753cf747d9b9250ba8ba0d737d
Boot ID: c1989633a9a34eaf8a9d725b8ac0cf6e
Virtualization: oracle
Operating System: Debian GNU/Linux 10 (buster)
Kernel: Linux 4.19.0-6-amd64
Architecture: x86-64
Persistent hostname
Set static (persistent) hostname that will be preserved across a reboot.
$ sudo hostnamectl --static set-hostname debian.localhost.localdomain
Display current static hostname.
$ hostnamectl --static debian.localhost.localdomain
hostname file will be updated accordingly.
$ cat /etc/hostname debian.localhost.localdomain
Remember to update /etc/hosts static table lookup for hostnames.
Transient hostname
Transient hostname can be used only in a specific situation where persistent hostname is set to
localhost, localhost.localdomain or ends with these names (like debian.localhost.localdomain). See additional notes at the end.Set transient (not persistent) hostname that will be overwritten after system reboot.
$ sudo hostnamectl --transient set-hostname debian
Current hostname will be updated immediately.
$ hostname debian
$ sudo sysctl kernel.hostname kernel.hostname = debian
Static hostname will be not altered, so this change will be not preserved across a reboot.
$ hostnamectl --static debian.localhost.localdomain
$ cat /etc/hostname debian.localhost.localdomain
Display current transient hostname.
$ hostnamectl --transient debian
Display hostname settings to notice additional line with transient hostname.
$ hostnamectl
Static hostname: debian.localhost.localdomain
Transient hostname: debian
Icon name: computer-vm
Chassis: vm
Machine ID: 5b1a78753cf747d9b9250ba8b a0d737d
Boot ID: 29280923e1624358b2b485af48d4c5e7
Virtualization: oracle
Operating System: Debian GNU/Linux 10 (buster)
Kernel: Linux 4.19.0-6-amd64
Architecture: x86-64
Remember to update /etc/hosts static table lookup for hostnames.
Supplementary settings
Set pretty hostname.
$ sudo hostnamectl --pretty set-hostname "My computer"
Set host icon.
$ sudo hostnamectl set-icon-name linux-vm
Set host chassis.
$ sudo hostnamectl set-chassis vm
Set host deployment.
$ sudo hostnamectl set-deployment development
Set host location.
$ sudo hostnamectl set-location "Berlin, Germany"
These settings are stored in /etc/machine-info file.
$ cat /etc/machine-info PRETTY_HOSTNAME="My computer" ICON_NAME=linux-vm CHASSIS=vm DEPLOYMENT=development LOCATION="Berlin, Germany"
Use these settings at your discretion.
System service
Functionality described here is provided by the Hostname Service.
$ sudo systemctl status systemd-hostnamed.service
● systemd-hostnamed.service - Hostname Service
Loaded: loaded (/lib/systemd/system/systemd-hostnamed.service; static; vendor preset: enabled)
Active: inactive (dead)
Docs: man:systemd-hostnamed.service(8)
man:hostname(5)
man:machine-info(5)
https://www.freedesktop.org/wiki/Software/systemd/hostnamed
Dec 18 21:03:34 debian systemd[1]: Started Hostname Service.
Dec 18 21:03:34 debian systemd-hostnamed[1409]: Changed pretty host name to 'My computer'
Dec 18 21:04:05 debian systemd[1]: systemd-hostnamed.service: Succeeded.
Dec 18 21:09:58 debian systemd[1]: Starting Hostname Service...
Dec 18 21:09:58 debian systemd[1]: Started Hostname Service.
Dec 18 21:09:58 debian systemd-hostnamed[1566]: Changed icon name to 'linux-vm'
Dec 18 21:10:14 debian systemd-hostnamed[1566]: Changed chassis to 'vm'
Dec 18 21:10:19 debian systemd-hostnamed[1566]: Changed deployment to 'development'
Dec 18 21:10:26 debian systemd-hostnamed[1566]: Changed location to 'Berlin, Germany'
Dec 18 21:10:56 debian systemd[1]: systemd-hostnamed.service: Succeeded.
Additional notes
Inspect following code snippets to understand in detail how it works.
Source file src/hostname/hostnamed.c
static int context_update_kernel_hostname(Context *c) {
const char *static_hn;
const char *hn;
assert(c);
static_hn = c->data[PROP_STATIC_HOSTNAME];
/* /etc/hostname with something other than "localhost"
* has the highest preference ... */
if (hostname_is_useful(static_hn))
hn = static_hn;
/* ... the transient host name, (ie: DHCP) comes next ... */
else if (!isempty(c->data[PROP_HOSTNAME]))
hn = c->data[PROP_HOSTNAME];
/* ... fallback to static "localhost.*" ignored above ... */
else if (!isempty(static_hn))
hn = static_hn;
/* ... and the ultimate fallback */
else
hn = FALLBACK_HOSTNAME;
if (sethostname_idempotent(hn) < 0)
return -errno;
(void) nscd_flush_cache(STRV_MAKE("hosts"));
return 0;
}
static bool hostname_is_useful(const char *hn) {
return !isempty(hn) && !is_localhost(hn);
}
Source file src/basic/hostname-util.c
bool is_localhost(const char *hostname) {
assert(hostname);
/* This tries to identify local host and domain names
* described in RFC6761 plus the redhatism of localdomain */
return strcaseeq(hostname, "localhost") ||
strcaseeq(hostname, "localhost.") ||
strcaseeq(hostname, "localhost.localdomain") ||
strcaseeq(hostname, "localhost.localdomain.") ||
endswith_no_case(hostname, ".localhost") ||
endswith_no_case(hostname, ".localhost.") ||
endswith_no_case(hostname, ".localhost.localdomain") ||
endswith_no_case(hostname, ".localhost.localdomain.");
}
Source file meson.build
conf.set_quoted('FALLBACK_HOSTNAME', get_option('fallback-hostname'))
Source file meson_options.txt
option('fallback-hostname', type : 'string', value : 'localhost',
description : 'the hostname used if none configured')
Source file src/hostname/hostnamed.c
r = parse_env_file(NULL, "/etc/machine-info",
"PRETTY_HOSTNAME", &c->data[PROP_PRETTY_HOSTNAME],
"ICON_NAME", &c->data[PROP_ICON_NAME],
"CHASSIS", &c->data[PROP_CHASSIS],
"DEPLOYMENT", &c->data[PROP_DEPLOYMENT],
"LOCATION", &c->data[PROP_LOCATION]);