# Hostname / Host ID

## <mark style="color:red;">Commands</mark>

<table data-header-hidden data-full-width="true"><thead><tr><th>Command</th><th>Description</th></tr></thead><tbody><tr><td><mark style="color:yellow;"><code>cat /proc/sys/kernel/hostname</code></mark></td><td>Hostname directly from the kernel's hostname file.</td></tr><tr><td><mark style="color:yellow;"><code>hostname</code></mark></td><td>Displays the hostname.</td></tr><tr><td><mark style="color:yellow;"><code>uname -n</code></mark></td><td>Displays just the hostname.</td></tr><tr><td><mark style="color:yellow;"><code>hostnamectl</code></mark></td><td>*systemd systems - Most comprehensive hostname info</td></tr><tr><td><mark style="color:yellow;"><code>cat /etc/hostname</code></mark></td><td>Displays the hostname stored in the /etc/hostname file.</td></tr><tr><td><mark style="color:yellow;"><code>hostid</code></mark></td><td>Prints the numeric identifier for the current host.</td></tr></tbody></table>

Multiple hostnames: A system can have different hostnames configured for various purposes.

### <mark style="color:purple;">Static vs. Transient</mark>

<mark style="color:yellow;">`hostnamectl`</mark> distinguishes between static (set in configuration files) and transient (set at runtime) hostnames.

## <mark style="color:red;">File Locations</mark>

<table data-header-hidden data-full-width="true"><thead><tr><th width="326">Path</th><th>Description</th></tr></thead><tbody><tr><td>/etc/hostname</td><td>On many Linux distributions such as Debian and Ubuntu, stores the system's hostname.</td></tr><tr><td>/etc/hosts</td><td>Contains mappings of IP addresses to hostnames, often includes the system's hostname for the loopback interface.</td></tr><tr><td>/etc/sysconfig/network</td><td>On Red Hat-based distributions like Red Hat Enterprise Linux (RHEL) and CentOS, sets the system's hostname.</td></tr><tr><td>/etc/rc.conf or /etc/rc.conf.local</td><td>On some Unix systems like FreeBSD, stores the hostname information.</td></tr><tr><td>Dynamic Host Configuration Protocol</td><td>In network configurations using DHCP, the hostname may be assigned dynamically by the DHCP server.</td></tr><tr><td>hostname command</td><td>Used to view or change the hostname temporarily during a session.</td></tr><tr><td>Network Configuration Files</td><td>Some Unix distributions store hostname information in network configuration files.</td></tr><tr><td>NIS/NIS+</td><td>In network environments using NIS or NIS+ for centralized authentication and configuration management.</td></tr></tbody></table>


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://www.shellspells.net/linux/system-ops/system-info/hostname-host-id.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.