hostname command in Linux: machine names and resolution, examples

Overview

Plain hostname prints the current node name. This identifies a machine, not a user, and need not be a fully qualified DNS name. The utility can also change the name, so adding an operand changes the purpose of the invocation.

A fully qualified domain name, or FQDN, depends on system name resolution. The source can be /etc/hosts or DNS according to the resolver configuration. Adding a dotted name does not automatically create a valid DNS record.

Options

14

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Option case matters: -i resolves addresses for the host name, whereas -I enumerates interface addresses without relying on resolution of that name. The -I result excludes loopback and IPv6 link-local addresses; order is not guaranteed. Neither option means “public IP”.

-F reads a name from a file and changes state. A plain hostname operand also sets the current node name. For persistent Ubuntu configuration, use hostnamectl and check local name resolution.

Option	What it does	Example
`-a` `--alias`	Aliases obtained through name resolution.	`hostname -a`
`-f` `--fqdn`	The resolved fully qualified host name.	`hostname -f`
`-i` `--ip-address`	Addresses obtained by resolving the current host name.	`hostname -i`
`-I` `--all-ip-addresses`	Interface addresses excluding loopback and IPv6 link-local.	`hostname -I`
`-s` `--short`	The short name before the first dot.	`hostname -s`
`-A` `--all-fqdns`	Resolved FQDNs for interface addresses, not a single canonical identity.	`hostname -A`
`-b` `--boot`	Use a default name if none is available; a setting mode. dangerous	`hostname -b`
`-d` `--domain`	The DNS domain from the resolved FQDN, not the resolver search list.	`hostname -d`
`--long`	Synonym for --fqdn.	`hostname --long`
`-F` `--file` file	Read a name from a file and set it. dangerous	`hostname -F ./hostname.txt`
`-y` `--yp`	The NIS/YP domain, not the DNS domain.	`hostname -y`
`--nis`	Synonym for --yp.	`hostname --nis`
`-V` `--version`	Installed utility version.	`hostname -V`
`-h` `--help`	Display help and exit.	`hostname -h`

Nothing found. Try a shorter query.

Recipes

3

Identify the server before making changes

Check the node name alongside the user identity. These are independent properties.

bash

hostname
whoami

Check resolution of the current name

getent queries the configured system name sources. A result does not prove that DNS supplied it.

bash

getent hosts "$(hostname)"
hostname -f

Compare resolved and interface addresses

Different name and interface configuration can legitimately produce different results. Inspect ip for details.

bash

hostname -i
hostname -I
ip address

Troubleshooting

3

A short name works but the FQDN does not

Check how the system resolver handles the current name. Do not rename the machine merely to suppress the error.

bash

hostname
getent hosts "$(hostname)"

hostname -I returned several addresses

A machine may have several interfaces and addresses. Do not treat the first result as universally correct; match it to the intended network.

bash

ip address

The old name returned after reboot

A temporary change does not replace persistent configuration. Inspect hostnamectl and /etc/hostname; external provisioning can also change the name.

bash

hostnamectl
cat /etc/hostname

Danger zone

Danger. hostname new-name and hostname -F file change the name when privileges permit. This can disrupt expected resolution and dependent services. The cheat sheet above only reads information. Do not rename a machine to “fix DNS” without diagnosing the cause.

hostname — machine names and resolution

Cheat sheet

Overview

Options

Recipes

Identify the server before making changes

Check resolution of the current name

Compare resolved and interface addresses

Troubleshooting

A short name works but the FQDN does not

hostname -I returned several addresses

The old name returned after reboot

Danger zone

See also